ServoMagazine_11-2003

Circle #32 on the Reader Service Card.Circle #106 on the Reader Service Card. SERVO 11.2003 79

Vol. 1 N

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Control many thingsat the same time!

To order, or for more info on the ServoPod , Visit us at www.newmicros.com, or call 214-339-2204 ™

With ServoPod™, you can do many things at the same time.You can control a LCD, keypad; and 16 analog rangers and 25 servos, at once; or instead 16 analog rangers 6 axes of quadrature encoded servo motors; or 16 motors with channels of analog feedback. ServoPod™ handles them all with ease. The innovative operating system/language, IsoMax™, is interactive and inherently multitasking, and makes a “Virtually Parallel Machine Architecture™”. New Micros, Inc. applied 20 years experience designing embedded microcontrollers, to perfected this powerful 2.3” x 3” board, with a feature-rich 80MHz DSP processor including: 2 S C I , S P I , C A N , 1 6 A / D , 1 2 P W M , 1 6 M u l t i m o d e T i m e r s , G P I O . . . ServoPod™ with IsoMax(TM) is only available from New Micros, Inc. Kit $199

ServoPod™!

If you’re serious about robotics and motion control, you must have a ServoPod™If you’re serious about robotics and motion control, you must have a ServoPod™

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features

16 ALWAYS ON ROBOTICS

71 NEURONS FOR ROBOTS

74 WHAT WOULD YOU TRUSTA ROBOT TO DO?

SERVO Magazine ((IISSSSNN 11554466--00559922//CCDDNN PPuubb AAggrreeee##4400770022553300)) is published monthly for $24.95 per year by T & L Publications, Inc., 430 Princeland Court, Corona, CA 92879.PERIODICALS PENDING AT CORONA, CA AND AT ADDITIONAL MAILING OFFICES. POSTMASTER: Send address changes to SERVO Magazine, 430 PrincelandCourt, Corona, CA 92879-1300 or Station A, P.O. Box 54,Windsor ON N9A 6J5.

4 SERVO 11.2003

8 STARS OF THESILVER SILKSCREEN

Cover Photo by Keith Hamshere.Lucasfilm & . All rights reserved.

11.2003

Photo by Giles Keyte

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columns departmentsprojects

34 Low Cost Sound Sensor

38 Battery Fuel Gauge

42 Hexatron - Part 1

52 SOZBOTS - Part 2

56 The Head Tracker

6 Mind/Iron

21 Ask Mr. Roboto

24 GeerHead

29 Menagerie

62 Robytes

64 Events Calendar

66 Robotics Resources

78 Appetizer

6 Publisher’s Info

30 New Products

33 Robot Bookstore

65 Robotics Showcase

78 Advertiser’s Index

SERVO 11.2003 5

Vol. 1 No. 1

Robosaurus

Coming 12.2003 in SERVO

table oof ccontents

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Published Monthly By The TechTrax Group — A Division Of

T & L Publications, Inc.430 Princeland Court

Corona, CA 92879-1300(909) 371-8497

FAX (909) 371-3052www.servomagazine.com

Subscription Order ONLY Line1-800-783-4624

PUBLISHERLarry Lemieux

[email protected]

ASSOCIATE PUBLISHER/VP OF ADVERTISING SALES

Robin [email protected]

MANAGING/TECHNICAL EDITORDan Danknick

[email protected]

CIRCULATION DIRECTORMary Gamar

[email protected]

WEB CONTENT/STOREMichael Kaudze

[email protected]

PRODUCTION/GRAPHICSRosa Gutierrez

Shannon Lemieux

DATA ENTRYKarla Thompson

Dixie Moshy

OUR PET ROBOTSGuidoMifune

Copyright 2003 by T & L Publications, Inc.

All Rights Reserved

All advertising is subject to publisher's approval.We are not responsible for mistakes, misprints,or typographical errors. SERVO Magazineassumes no responsibility for the availability orcondition of advertised items or for the honestyof the advertiser.The publisher makes no claimsfor the legality of any item advertised in SERVO.This is the sole responsibility of the advertiser.Advertisers and their agencies agree toindemnify and protect the publisher from anyand all claims, action, or expense arising fromadvertising placed in SERVO. Please send allsubscription orders, correspondence, UPS,overnight mail, and artwork to: 430 PrincelandCourt, Corona, CA 92879.

by Dan Danknick

My friend Dave has an Emailtagline that makes melaugh every time I read it:

"The revolution will be digitized."It is both superficially funny, aswell as secretly sublime. As anengineer, I know that once Idigitize a sample from thecontinuum, I can filter, convolve,store, and express it according tomy desire. Although I don't havecontrol over the fields of nature, Iget to choose how I extractinformation.

And that is exactly whatSERVO Magazine is all about —separating raw data frommeaning.

Although we started workingfull-time on this many monthsago, the foundation was laid lastyear when the first AmateurRobotics Supplement showed upwith the June issue of Nuts &Volts Magazine. It wasn't that weproduced it — but rather that you,the hobbyist and technologist,consumed it. So like the skips of astone upon water that growcloser, our publication datescontracted to a monthly interval.And now there are many ripples.

This magazine spans theGaussian curve, from recreationalreading to homeworkassignment. I expect it to be asmuch at home on a coffee tableas getting splattered with fluxremover and tapping fluid on theworkbench. I want it to consumeyour thoughts on the drive home,

inspire arguments at your nextrobotics club meeting, and fill youwith the unspoken optimism thattechnology promises.

I have an A-Team of writers.From Forth evangelists toresearchers in cognitiveheuristics, there is no facet ofrobotics that will escape ourcollective gaze. I am ascomfortable publishing thedetails of CANBUS identifieracceptance registers as I am withQ-learning algorithms and themotion control system in R2D2(see page 14).

Our currency is ideas.Whether they originate from anelectronics inventor in NewZealand, a C++ programmer inhigh school, or an MIT professorworking in the private sector —we are striving to become theFederal Reserve Bank of therobotics movement. Every projectpresents an obvious benefit inaddition to a covert one. We onlyask that you show up with awillingness to think.

But if you wish to interact, wewelcome that too — check outthe Mr. Roboto Q&A column(page 21) and the Menagerie,where you can share yourcreation with our readership(page 29). The conduit movesinformation both ways.

And if you act today, you'lleven get to choose which side ofthe A/D converter you wish to beon during the revolution.

6 SERVO 11.2003

Mind / Iron

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SUBSCRIBE NOW!12 issues for $24.95www.servomagazine.com or call toll free 1-800-783-4624

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The movie industry has longbeen fascinated with robots,dating back to shortly after

the word was coined. In a way, it'snot all that surprising given robots'theatrical origin: The word robot wasfirst used in 1920 by Czechoslovakianauthor Karel Capek, who derived itfrom robota — a Czech word meaningserf or slave. When Capek's playabout the dehumanization of man,R.U.R. (short for Rossum's UniversalRobots), was translated into English,the word robot was quickly absorbedinto the English language.

The first movie robot appearedshortly thereafter — "Maria" from FritzLang's 1927 epochal film Metropolis.If her slender golden shape remindsyou of another robot who made hiscinematic debut 50 years later, consid-er the words of Ralph McQuarrie(www.ralphmcquarrie.com), theindustrial artist George Lucas hired tocreate the initial illustrations thathelped sell Star Wars to 20th CenturyFox. “George talked about C-3P0 asbeing a robot that looked similar tothe Metropolis robot in Fritz Lang'sfilm. Well, that was a girl, Georgesaid, make it a boy.” In a way, C-3P0'spopularity has helped bolsterMetropolis' popularity because of theconnection between the two robots.

Metropolis' theme of oppressedworkers in stifling cities was verymuch in keeping with many of theconcerns of 1920s intellectuals, ascommunism had only recentlybecome a reality in the Soviet Union,and fascism would soon be on therise as well. Of course, as David Stork(http://rii.ricoh.com/~stork), the

author of Hal's Legacy (MIT Press,ISBN: 0262692112) has noted,"Science fiction is often about thetime it's written, more than the timeit's depicting."

(Obviously, as we move forward,we're going to overlook some favoritemovie and TV robots in this piece —there just isn't time to go over everyrobot to clank through a soundstage.But hopefully we won't miss toomany of the milestones.)

Robbie: The Man inthe PolypropyleneSuit

Robots largely took a back seat inthe movies until the 1950s, when avariety of forces converged to allowthe decade that brought us The ManIn The Gray Flannel Suit to also bringus men in the oversized moldedpolypropylene suits, including one ofthe most famous movie robots:Robbie.

As Peter Abrahamson, (home.pacbell.net/roninsfx) the founder ofRonin Special Effects (and a fine robotbuilder himself) says, “I really enjoyrobots that have character, and that'sone of the reasons why I love Robbie somuch. Because Robbie was great, eventhough he was a robot, he really had acertain coolness to him. He had agreat character about him.” Robbie'scharacter is enhanced by the tensioncreated by his somewhat menacingblack form and booming mechanicalvoice, and his initial ambivalence as acharacter — until the end of the film,it's hard to tell whose side he's on. By

the end of Forbidden Planet, as hepilots the “United Planets” spacecrafthome to Earth, it's clear he's one ofthe good guys, and well accepted bythe crew.

Of course, Robbie requires a cer-tain suspension of disbelief from theaudience — his anthropomorphicshape makes it fairly obvious thatthere's a man inside him. Zack Bieber,owner of The Machine Lab(www.themachinelab.com), saysthat in addition to the limitations ofmovie special effects, “Robots need-ed to be human-like to install any kindof emotion in the audience. Youknow the robot is angry when itbangs its fist into the spaceship,because that's something that ahuman would do. So to convey thatemotion, you had to depict somethingthat the viewer could relate to.”

Life Inside a MachinePerhaps the first great change in

what a robot could look like occurredin Stanley Kubrick's 1968 film, 2001:A Space Odyssey, which to many crit-ics (and fans alike) is not only thegreatest science fiction film evermade, but a watershed moment inmovie history.

Kubrick wanted to show howman evolved from primitive apes(with a powerful assist from a God-like monolith) to his present form.Kubrick gave his audiences two possi-ble successors to mankind: HAL, asentient super-computer, and theNietzsche-inspired "Superman" (norelation to Clark Kent) that KeirDullea's Dave Bowman character

ROBOTS WITH CHARACTER. ROBOTS ENHANCED.

by Ed Driscoll, Jr.

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evolves into at the end of the film. HAL, who controls the Discovery

— the film's main spacecraft — is essen-tially an intelligent robot that theastronauts live inside of. (In a way, heanticipates the world of The Matrix,where the Earth's entire civilizationexists inside a supercomputer.) HALoriginally began life as a mobile robot,but given the limits of mid-1960s spe-cial effects, and Kubrick's fear that2001 would resemble previous sciencefiction films, “I think from a cinematicpoint of view, it's just far more effec-tive to be enveloped in the computer,”David Stork notes, than it is to have itas another actor playing a robot that isalongside the characters onscreen.

Silent RunningThrough the Empire

Hal was the springboard for sever-al robots in the 1970s that began tolook less and less like men as theirshapes diversified. Not coincidentally,this was also the decade that high-tech began to play an increasing rolein real life, as robots began showingup on assembly lines, and the person-

al computer became a reality. The first big change occurred in

1972's Silent Running. As a film, it'saged rather badly — its somber eco-ter-rorist plot may have seemed hip in theearly 1970s, but now feels dangerous-ly realistic. But as a repository for bril-liant special effects, Silent Running ishard to top. Its three 'drones' — Huey,Dewey, and Louie — were arguably thefirst movie robots to not look like menin rubber suits.

Of course, that's exactly whatthey were — Douglas Trumbull, thefilm's director, hired three actors whohad lost their legs, and then designedthe plastic costumes around their bod-ies. Once encased in them, the actorswalked on their hands, which were inthe rubber and plastic feet of therobot costumes. It's an amazingly real-istic effect that holds up quite well.

Silent Running's three dronesbecame the inspiration for one of themost popular movie robots of all time— R2-D2. Along with his companion,the equally famous C-3P0, R2 and heare the non-human glue that holds allof the Star Wars films together.

In fact, it's interesting to compare

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R2 and C-3P0, and their audienceacceptance: the heroic, brave “Artoo,”who constantly saves the day in the StarWars films (even getting "killed" andrebuilt at the end of Episode IV) is farmore popular than the prissy, cowardlyC-3P0, even though C-3P0 has an obvi-ously human shape, and can speakEnglish. And the sprightly Huey, Dewey,and Louie steal Silent Running right outfrom Bruce Dern's morose character.

The 1980s: TheDecade of theAndroid

Inspired by the success of the firstStar Wars trilogy, the 1980s sparked anexplosion of science fiction in themovies and on TV, and with it, cameseveral interesting robotic characters.

In contrast to the non-human robot-ic stars of the 1970s, the 1980s saw atrend of robots designed to pass forhumans. In other words — androids.

In the Star Wars films, the word“droid,” an abbreviation of android, isused to refer to all of the robotsonscreen, no matter what their form.But according to Webster's dictionary,the word “android” dates back evenfurther than the word “robot,” to circa

1751, and is based on the Greek wordandroeides, which means, not surpris-ingly, “manlike.”

In the 1980s, man-like androidswere featured in the first three Alienfilms, the 1983 cult classic BladeRunner, The Terminator films, and onTV, with Mr. Data in Star Trek: The NextGeneration, who later made the jumpto the movies, along with the rest ofthe Next Generation cast.

It's probably not a coincidence thatthese androids became popular just asthe postmodern crowd began askingwhat exactly man was — did he have asoul? Or was he merely a machine him-self?

Of course, fans of movie specialeffects would argue that these androidsbegan appearing in the movies notbecause of trendy po-mo philosophiz-ing, but because movie special effectsbecame sophisticated enough to createeffects such as the metallic skeletonunderneath Arnold Schwarzenegger'sTerminator character, and the evenmore impressive liquid metal of the

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shape shifting terminators played byRobert Patrick in T2 and the beautifulKristanna Loken in T3.

Perhaps the most beloved android isStar Trek: The Next Generation's Mr. Datawho, like HAL, is an intelligent, sentientmachine. But unlike HAL and theTerminator robots who apparently feelthey are superior beings, Data, likePinocchio, wants to be human. At firstglance, Data's Pinocchio-like quest appearsto be a Blade Runner homage. But DavidGerrold (www.gerrold.com), the sciencefiction author who created the much-lovedtribbles for the original Star Trek, andhelped develop The Next Generation, saysthat “The most likely antecedent wasGene's show, The Questor Tapes,” a failedTV pilot written by Star Trek's creator GeneRoddenberry in the mid-1970s.

Gerrold, who has two books, The ManWho Folded Himself and The Martian Child(both recently released in trade paperback)says, “We wanted a character who wouldtake on the responsibilities of Spock, butwe didn't want another Vulcan. So wedecided to do the opposite of Spock-anandroid who would be like Pinocchio. Hewants to become a 'real boy.' Gene came

up with the name Data, despite the factthat just about everybody else hated it.”

Fortunately, the audience didn't seemto mind Data's name. And like Spock,because Data allows us to see mankindfrom an outsider's viewpoint, Databecame a science fiction superstar — evenif he never did quite become a man.

The 1990s: Is Life But aDream?

The postmodernists of the 1980sdebated “what is man” with android char-acters like Data. Movie postmodernists ofthe 1990s could argue, "what is reality?"because by the late 1990s, digital specialeffects radically changed the scope ofwhat movies could present.

The Matrix trilogy takes 2001's themeof living in a spaceship controlled by acomputer to its ultimate conclusion: Whatif your very existence is an illusion createdby a computer? The result is a wild ride, asinside the Matrix, the human characterssuch as Neo, Morpheus, and Trinity fightholographic androids in the form of AgentSmith and his cohorts. And outside theMatrix, our intrepid trio fights the evil-look-

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ing robotic Sentinels. All of which arecontrolled by a central computer,which uses humans as “living batter-ies.” (Or at least that's what we knowfrom the first two movies. The lastfilm in the trilogy, Matrix Revolutions,hasn't been released at the time thisarticle is being written, and promisesadditional mind-blowing plot twists.)

The EvolutionContinues

Based on a concept developedby Stanley Kubrick, Steven Spielberg'sA.I. is a maddeningly inconsistentfilm, but it shows a world in whichrobots are evolving far faster thanman is. David, the Pinocchio-like boyplayed by the charismatic youngactor Haley Joel Osment, is yearsbeyond our current technology. Butby the end of the film, he meets upwith even more advanced robots,which control planet Earth thousands

of years in the future, after mankindis extinct. Of course, our current levelof technology is nowhere near David,Hal, R2, or the Matrix (I think … say,who was that fellow in the black suitand tie clip following me last night??)But robots, as this new magazinedemonstrates, are increasingly allaround us. And artificial intelligencewill be a reality as well — someday.But as David Stork notes, “It's goingto be many, many decades. Or asJohn McCarthy said, it will either bewithin four, or four hundred years,and it depends on getting twoEinsteins and three Von Neumanns-you can't predict it; it could be soon,or might not be.”

In any case, the movies have givenus a wonderful sneak preview intoour biomechanical future.

SERVO 11.2003 13

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(c) Lucasfilm & TM. All rights reserved.Digital work by Industrial Light & Magic.

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“Hey, this R2 unit of your seems a bitbeat up. Do you want a new one?”

“Not on your life! That little droid andI have been through a lot together.”

R2-D2 is such a popular movie robot,and so beloved by many readers of Nuts &Volts and Servo, that we wanted to inter-view the man who controls him, to findout exactly what's going on underneathR2's silver and blue dome.

Don Bies (www.starwars.com/bio/donbies.html) began with Industrial Lightand Magic in 1987 as a puppeteer on TheWitches of Eastwick, and later that yearjoined Lucasfilm Ltd., as R2-D2's operatorfor a series of Japanese commercials. Sincethen, he's controlled R2 on each of the lat-est trilogy of Star Wars films, including itsfinal chapter (apparently titled, if youbelieve the Internet rumors, Star Wars:Episode III: An Empire Divided, which obvi-ously is subject to change), due for releasein May of 2005. As he's in Australia, shoot-ing that film's live action sequences, wespoke with Bies by phone.

Bies says that mechanically, R2 is actu-ally quite simple. “We've got two wheel-chair motors in the left and right foot. And

then the front foot is a caster. For the headturn, we just directly attached a big chunkyservo, and it works pretty well.”

Ever since Episode I, Bies has usedFutaba 9ZAP nine channel model airplaneradio control units to operate R2. Essentiallystock, their batteries have been replaced byMakita batteries for longer life.

“We have a Vantec speed control(www.vantec.com) to control themotors. It drives off of one stick, and it'sdone through the Futaba radio transmitter.So I can just push this one stick forwardand the robot runs forward. And if I pushit backward, it goes back, and left goesleft, and right goes right, as opposed tohaving two stick controls, as in a tankdrive.”

Back to the FutureWhile the current Stars Wars trilogy

features gobs of cutting-edge digital tech-nology, much of its production designowes its lineage to the first round of Star

Inside The World'sMost Popular Droid

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Wars films, back when movie specialeffects were far less sophisticated.

While R2's basic shape came from theseminal illustrations that George Lucas hadpainted by industrial artist Ralph McQuarrie,his design was finalized by John Stears, whoheaded the British on-stage special effectsdepartment of Star Wars' original sound-stage — EMI's Elstree studios.

The many documentaries made dur-ing the shooting of those first Star Warsfilms featured numerous shots of radiocontrolled R2s crashing into walls, or sim-ply refusing to move on cue. Bies admitsthat the original R2s “had a lot of prob-lems, because the R/C technology at thetime was pretty much in its infancy. Butsince then, the radio control units them-selves have become very, very stable.”

The stability of those controls allowsBies to effectively think like an actor whenhe's on set, “to a certain extent. I don'twant to sound like I'm doing brain surgeryor anything,” because R2 is “so limited inwhat it can do — the head can turn, andwe have the little holographic eye thatmoves up and down, so you can get a lit-tle motion out of that. I think that 90 per-

cent of R2's character comes out of thesounds that they put in later, so you get allthose movements in with the bleep or thesad whistle or whatever.”

The Man Inside ArtooOf course, R2 has another handler —

since the mid-1970s, three foot, eight inchtall Kenny Baker (www.kennybaker.co.uk)has often been inside of him. In the origi-nal films, in most shots where R2 wasshown waddling on two legs, Baker wasinside. For George Lucas and the rest of theoriginal Star Wars production team, havingan actor inside of Artoo was often far morereliable than the R/C controls of the time.

For better or worse, technology hasrendered Baker increasingly superfluous tothe latest trilogy. “Kenny's been used lessand less,” according to Bies, “partiallybecause of the stability and the reliabilityof the R2 units, and partially because R2 isgoing more in the digital route. In EpisodeI, Kenny was in the film a fair amount,whenever there's a two-legged version. InEpisode II, we didn't use Kenny at all inAustralia — we were able to do everythingwith the radio-controlled units. And if we

needed a two-legged R2 for a shot, itwould typically be me just hiding behind,or underneath it wiggling it around whennecessary, with a radio-controlled headthat we put on it, so that it could turn itshead back and forth.”

Bies says that it was out of courtesy toBaker that Lucas allowed him to control R2for one shot in Episode II. And Bies is sureBaker will be inside R2 for a shot or two inEpisode III, as well. The films just wouldn'tlook right without Baker getting a screencredit for portraying R2.

And digital effects are reducing Bies'srole with R2, as well. “On Episode II, some-body did a shot count, and there weresomething like 96 R2 shots in the film, and14 of them were digital R2s, there was oneKenny shot, and then the rest were mewith the radio controlled units. WithEpisode III, it's too early to tell, but R2 hasa bigger role in the film, and has moreaction sequences, so there will probablyend up being more digital shots of R2 inthe picture.”

Of course, whether he's radio con-trolled, actor controlled, or digital, R2 willalways be a hero to movie fans.

Perform proportional speed, direction, and steering withonly two Radio/Control channels for vehicles using two

separate brush-type electric motors mounted right and leftwith our mixing RDFR dual speed control. Used in manysuccessful competitive robots. Single joystick operation: upgoes straight ahead, down is reverse. Pure right or left twirlsvehicle as motors turn opposite directions. In between stickpositions completely proportional. Plugs in like a servo toyour Futaba, JR, Hitec, or similar radio. Compatible with gyrosteering stabilization. Various volt and amp sizes available.The RDFR47E 55V 75A per motor unit pictured above.www.vantec.com

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IntroductionScience fiction stories have always set the standards for

what people expect from "real" robotic creations. Books andmovies like I, Robot, Silent Running, and Short Circuit por-tray robots that exhibit intelligence, resourcefulness, autono-my, self-preservation and other sophisticated behaviors.

Consider the famous odd couple from the Star Warsseries — R2-D2 and C-3PO. They navigate their environments,communicate with each other, and plan rescues of them-selves and their human counterparts. Even though we findthese fantasy robots captivating and compelling, their highlevel abilities do not exist in present day robots, but remainthe exclusive domain of "living systems."

Witness the long and thus-far fruitless efforts to createtrue "artificial intelligence." Even "Deep Blue," IBM's special-ized chess playing computer which soundly defeated humanchess champ Garry Kasparov in 1997, has nothing near theabilities of the fictional HAL 9000 computer in the classicmotion picture 2001: A Space Odyssey.

The many assumptions — both stated and unstated —that lurk behind science fiction robots provide robot builderswith many daunting challenges. Consider the issue of power.

Power ChallengeIn the classic TV series Lost In Space, robot B-9 had its

own station aboard the Jupiter 2 spaceship and regularlyreturned there for recharging.

Likewise, R2-D2 never exhibited a "low battery" conditionin the middle of a battle, or at any other time. The plucky lit-tle Astromech droid routinely located and accessed informa-tion ports conveniently placed throughout the Death Starand other Empire facilities. Though never directly explained inthe movie, droids like R2 evidently could also recharge them-selves as needed, without human intervention.

So the challenge that we as robot builders face in tryingto "make the future come true" lies in bridging the gap

between our imagination and what we can successfullybuild.

To understand that challenge, picture a simple modernrobot capable of "living" around your home. Assume it canrun for six hours on a set of four AA batteries. Operating 24hours a day, 7 days a week, and using regular alkaline cells,it would need a total of 5,840 batteries per year!

If the same robot used rechargeable batteries (a big costsavings, for sure) at four battery changes a day, you wouldperform 1,460 swaps per year — more than the number ofmeals you'll consume in the same time. With the robot requir-ing this kind of attention, you'd have to wonder who's theservant and who's the master!

So to significantly reduce the amount of "routine" atten-tion a robot requires from humans, our mission lies in findingways to endow the robot with the ability to reliably care forits own power needs.

Four Paths to Robot PowerLet's step back and take a look at the four general ways

that autonomous robots handle their needs for power hereat the start of the 21st century.

Path 1 — Live Fast, Die YoungRobots on this path use power at whatever rate they

need, but they neither sense nor "worry" about their reservesrunning out. When the batteries ultimately do die, so do therobots.

Most small and "toy" type robots use this approach. Theygenerally can continue operating even as their power levelsdrop, though they may move more slowly as this happens.

Path 2 — Spend What You EarnThese more frugal types of robots carry solar cells to

charge a storage device, then when they have gathered suf-ficient reserves they move, sometimes just in small jumps. Ofcourse, when the sun or other light source stops shining, the

16 SERVO 11.2003

by Roger Gilbertson

Power Challenges In “Always On”

Robotics

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SERVO 11.2003 17

robots stop too. When the light returns, they continue.Solar powered B.E.A.M.-type robots use this approach

to great success, but power availability generally limits theirsize, since larger robots usually need more power. (Allother factors remaining equal, as robot size increases themass goes up by the third power, but solar panel areaincreases only by the second power.)

Over the past 10 years, Sweden's major appliancecompany — Husqvarna — has fielded several models ofsolar powered lawn mowers to generally positive reviews.Resembling large beetles, the mowers exhibit flat top sur-faces covered in solar cells, and undersides with smallwhirling blades that continuously nibble at the lawn asthey careen randomly around the yard. A "perimeter wire"emitting a faint radio signal limits their zone of operation.

Path 3 — Do Your Thing, Then Call 911As this kind of robot loses its charge, falling power lev-

els can dramatically affect its performance, causing slowedmotions, delayed responses, and endangering its circuitry,its memory, and even nearby life forms.

To protect the robot itself from dangerous "brown out"conditions, as well as anything in the nearby environment(including robot inventors) from spastic or intermittentbehaviors, microprocessor controlled circuits often includelow-voltage detectors that shut the machine down beforeprocessing errors can occur.

All Path 3 robots monitor their own power levels, andthen modify their behaviors to conserve energy, compen-sate for slowed motors, etc. When voltages become toolow to operate properly, the robot may sound an alert,light an LED, or ask for assistance in some other way. Then,a human must step in and either provide power or returnthe robot to an appropriate charging station.

Many "home and garden" robots such as vacuumcleaners and lawn mowers indicate their power levels viacolored LEDs. Then they "rely on the kindness of strangers"to assist in their recharging process.

While this kind of robot offers better performancethan those having no means to compensate for decliningpower reserves, a robot that monitors its own power levelsstill depends on a human being in the life support cycle.Nonetheless, such robots have some awareness of theirown condition, and that puts them just a step away fromautonomously caring for their own needs.

Path 4 — Robot Feed Thyself!When a living creature gets hungry, it seeks out food.

Plants turn towards light, and large creatures eat smallerones. All living creatures survive due to this essential abili-ty to sense their own low energy and find sources toreplenish their reserves. Since an autonomous robotalready has the ability to navigate through its world, whyshould it not also seek out and acquire its own power? Itseems like a small jump, but in the past, too few robotshave attempted to do just this. One can't help but wonderif more of the early robots had incorporated this ability thatthey might still be on duty today.

Unfortunately, only a very small percentage of contem-porary robots have the ability to tend to their own recharg-ing. Some home, entertainment, and garden robots can,but they all carry prices well over $1,000.00. High perform-ance seems to carry a high price.

Given the low cost of powerful microprocessors, andthe wide availability of functional robot platforms, how canwe create a self-charging robot system priced within reachof hobbyists and experimenters?

This observation prompted my associates and I todevelop and produce the OctoBot Survivor, the first self-recharging robot kit for hobbyists and experimenterspriced at under $200.00.

The OctoBot Survivor StoryStarting in the fall of 2002, the design team from

Mondo-tronics and I began exploring the options availablefor building a self-charging robot so that students, hobby-ists, and experimenters could begin testing the boundariesof self-charging robots. For convenience and familiarity, westarted our project with many parts literally "off the shelf"from our RobotStore.com warehouse. Items such as theTwin Motor Gearbox and wide rubber tires from Tamiya,the Mini Dual H-bridge Driver Circuit, the Infrared ProximityDetector circuit, and others proved handy in creating work-

OctoBot fresh off the

charger.

Gilbertson.qxd 10/8/2003 10:36 PM Page 17

ing prototypes to test our initial concepts.Once we had a basic system working, our long time

collaborator and experimenter extraordinaire, ZachRadding, began writing the software routines. The outlinefor the brain's function went as follows:

On a full charge, the OctoBot will select one of twomodes: phototropic mode (active / "happy"), or photopho-bic (not as active / "sad"). On a battery low condition, theOctoBot will seek the charging station, stop when it makescontact with the station, and leave the station when thebatteries are charged.

Initially, the design called for two LEDs as the only out-put indicators, but Zach pushed for the addition of a smallspeaker as a way to "bring a little more life into the bot."We agreed to that, as long as the noises sounded pleasantrather than annoying.

During the "happy" and "sad" modes, we wanted therobot to exhibit a variety of behaviors such as object avoid-ance, light seeking, dark seeking, wall following, and ran-dom wandering. Zach created routines for making "emo-tive" tones that indicate the general state of the robot(without being annoying).

A PIC 16F876 microprocessor serves as the brain ofthe OctoBot. The robot carries six AA-size nickel metalhydride (NiMH) cells and the Dallas Semiconductor DS2436

— a compact battery charging-and-monitoring circuit.Another long time associate, Ed Severinghaus, contributedthe designs for the battery charging system, and relatedpower systems.

Once we worked out and tested the circuits, I beganthe layout of the main circuit board and many smaller sup-porting boards, and prepared the documentation andrelated materials.

Creature Features

As hobbyists ourselves, we wanted to include a greatdeal of expandability into the OctoBot. First of all, weadded a 24-pin DIP socket for a Stamp 2 processor andincluded connections from it to all of the sensors, and adirect line to the OctoBot's PIC brain. On start up, the PICbriefly "listens" to the socket, and if a Stamp responds, thePIC defers to the Stamp for commands. In this mode, thePIC remains very active, performing "low level" tasks such asmovements, seeking the charger, reporting on the batterycondition and such, thus freeing up the Stamp program forbigger tasks.

The OctoBot also has two expansion ports to supportuser-added circuitry. A 20-pin header rests at the center ofthe robot, and follows the Stamp Expansion Header formatfrom Parallax, Inc., makers of the BASIC Stamp processors.This header gives easy access to all the sensor signals andthe PIC processor, so that add-on boards can take control (inthe same way as the Stamp 2 socket), or can carry out otherfunctions.

The second, smaller expansion port on the bottom sideprovides power, ground, and four of the unassignedinput/output lines. This port makes it easy to add circuits forline following, edge detection, shaft encoders, and more.For our own development purposes, we first added an LCDdisplay to the 20-pin header, so that our programs couldreport on their conditions. We've since added RF modems,sonar boards, and a variety of other sensors. These projectsmay make their way into future articles.

OctoBot ChallengesJust as a fish finds itself well-adapted for life in water,

but operates poorly on land, a robot's featuresand abilities must also match its intended envi-ronment.

The OctoBot lives best in a fairly "safe" envi-ronment — with clearly visible walls, no suddendrop-offs, no water hazards or sand traps, andno narrow objects like chair legs. But theOctoBot welcomes other obstacles in its envi-ronment. The IR proximity sensors can detectnearly anything that reflects infrared light —cardboard boxes, wood blocks, sheets of paper,shoes — and experimenters can build their owncomplex and interesting environments for theirOctoBot, including light sources, areas of dark(caves for when exhibiting photophobic behav-

18 SERVO 11.2003

Opening the top reveals NiMH batteries(green) and 20-pin expansion header.

Block Diagramof OctoBot.

Gilbertson.qxd 10/8/2003 10:36 PM Page 18

iors), and more.Also, two or more OctoBots may

even inhabit the same space, since theycan easily detect the protective bodyshells of other OctoBots. However, inter-esting results can occur if two OctoBotsbecome hungry at the same time andattempt to share the same charger.(Darwinism may take over and only thefittest survive!)

If, for whatever reason, an OctoBotshould find itself running so low onpower that it cannot make it to a charg-ing station, it will end up "calling forhelp" by repeatedly uttering its startuptones. If not rescued by a human at some point, it will even-tually become too weak to even speak, and shut down untila human transports its lifeless shell back to a charging sta-tion. Then, resurrected by a fresh charge, it will continuewith its existence, unimpaired by the experience.

OctoBot ChoicesUnlike some of the more sophisticated self-charging

robots, the OctoBot contains no internal representation ofthe world, and no map or knowledge of its surroundings —it does not even store its "mood" but references that "emo-tion" directly from its battery voltage level. Likewise, theOctoBot need not perform any path planning or calculationsin order to return to its charger. Instead, it simply wandersin search of the charger's IR beacon (using its reflexiveresponses to avoid walls and obstacles along the way). Oncelocated, it moves toward the beacon until it makes contactwith the charger contacts. Then the on-board charging sys-tem monitors the batteries until fully charged (from one tothree hours).

In designing the OctoBot system, we observed someinteresting tradeoffs between various design choices. Onesituation involves the interplay between the light outputlevel of the IR beacon emitters, the abilities of the robot'sbeacon detectors, and the nature of objects in the environ-ment. In some cases, these three factors can combine tomislead the robot. Specifically, a brighter IR beacon mayallow the OctoBot to find it from farther away, but it alsosends light bouncing around to more places (IR reflects veryeasily). In a darkened room, the robot can end up searchingfor the beacon as if wandering in a house of mirrors — fol-lowing false reflections away from the charger, and eventu-ally dying a slow death chasing the "ghosts" of the beacon.

Another design interplay comes in setting the reservelevel of the robot's battery pack. An OctoBot that never ven-tures too far from its charger beacon (for example, if it livesin a smallish enclosure) would generally need little reservepower in order to drive itself back to the charger. However,an OctoBot living in a larger enclosure may require muchmore power in order to successfully locate the charger andreturn to it from farther away. So the question becomes, atwhat voltage should the robot begin searching for the

charger?In the end, we chose a reserve level in the middle of the

range — high enough that the OctoBot should have goodreserves to return from a fair distance away (the beacondetection system works to about three meters away), yetlow enough that the robot does not constantly feel theneed to feed.

A Day in the Life of "Asimov"So what does an OctoBot do with its time? For the pur-

poses of this article, I enlisted "Asimov," one of our oldestand most experienced OctoBots, and attached an RF radiolink to it so it could wirelessly report its status to a nearbyPC with an RF receiver. (This might also find its way as thesubject of a future article).

In this way, we recorded all the OctoBot's actions for aday or so, and then analyzed the results. The pie chart givesa summary account of a typical six hour period of its day.

Note how Asimov spends about two thirds of its timecharging (red). Nearly one third of its time involves doingvarious robot tasks around its enclosure (blue), or sitting qui-etly and blinking its LEDs (green). Notice how little time itactually spends in searching for the charger station (tan) —about one percent. These results indicate that Asimovwould probably perform well in a larger enclosure withmore obstacles, which would make for more interestingbehaviors while wandering, light and dark seeking, etc. Thiswould result in more challenging charger searches.

A Self-Charging Future?The OctoBot Survivor kit gives hobbyists and experi-

SERVO 11.2003 19

OctoBot, OctoBot Survivor, Always On, and Always On

Robotics are trademarks, and Mondo-tronics’ Robot Store

is a registered trademark of Mondo-tronics, Inc.

All other trademarks are of their respective holders.

F.Y.I.

Six hours in the life of OctoBot.

Gilbertson.qxd 10/8/2003 10:37 PM Page 19

menters the keys to unlock doors that lead to greater realmsof robot autonomy. We see many more directions to explorewith the OctoBot Survivor and its kin — developing betternavigational methods, expanding its range and endurance,increasing its ability to survive in more varied environments,and perhaps some day even the ability to operate outdoorsin more complex "real world" environments.

For technical information on the OctoBot SurvivorRobot kit, including assembly instructions, accessories,

examples of BASIC Stamp 2 code and more, please visit ourweb site at RobotStore.com

ConclusionEvery new technology pres-

ents us with opportunities tomake our world both safer, clean-er, and more productive, but alsomore complicated and even moredangerous.

As the builders of the future,we carry the great obligation toour descendants to create thebest that we possibly can, and toprepare ourselves for theinevitable changes that accompa-

ny every technological shift.The challenges of creating robots that care for their

own basic needs will continue to daunt us for many years.However, by following our science fiction dreams, and bydeveloping our own clear visions of what we want (and donot want) to achieve, students, hobbyists, and experi-menters of all levels can make significant contributions tothis exciting frontier. In time, our creations themselves mayturn to us and say, "Thanks!" Build more robots!

In college Roger G. Gilbertson studied engineering, robotics and the walking patterns of living creatures.

In 1987, he co-founded Mondo-tronics, Inc. to explore the commercial applications of Shape Memory Alloy wires,

and in 1995 launched RobotStore.com, the internet's first commercial robotics site. Mondo-tronics' Robot Store continues

to lead the field in presenting the best and most innovative new robot products for students, educators, hobbyists

and experimenters. Roger lives and works in Marin County, California, where an intelligent android has not yet managed

to get placed on the ballot for Governor.

About the Author

S

20 SERVO 11.2003

What anOctoBotdoes with

its day.

Gilbertson.qxd 10/8/2003 10:39 PM Page 20

Q.I want to build a robot withbig wheels in the back andsmaller ones in the front.

But I want each side to be driven by thesame output shaft from my gearbox.Obviously, I need to drive the largerwheel slower than the smaller one tokeep the linear speed the same. How doI compute the sprocket ratios for each? Iam going to use #25 chain.

— Anonymousvia Internet

A.You are correct about havingto drive the larger wheel witha lower RPM than the smaller

wheel. The short answer to your ques-tion is that the sprocket ratio must beexactly the same as the wheel ratio, andthe large sprocket must be mounted onthe large wheel. The #25 chain doesn'treally come into this decision processunless the torque loads on the chain cancause the chain to break, or weightbecomes too excessive.

The long answer in calculatingthe sprocket ratios for the wheelsbegins by calculating the ratios of thetwo wheel speeds, as a function ofthe two wheel diameters. Figure 1shows a simplified sketch of this typeof configuration. The linear velocity ofthe wheels is shown in Equation 1,where N is the rotational speed inRPM and D is the diameter of thewheel.

Since both of the wheels arerolling on the same surface, their lin-ear velocity will be equal (as shown inEquation 2). Equation 3 shows howthe wheel ratio affects the larger

wheel's speed as a function of the small-er wheel's speed. Since D1 is larger thanD2, the rotational speed of the largerwheel, N1, must be slower than thesmaller one, N2, which is in agreementwith your question.

To calculate the sprocket ratios, the

same type of an analysis is conducted.Instead of the ground connecting thewheel speeds together, a chain is usedto couple the sprocket speeds together.

Equation 4 shows how the sprocketdiameter ratios relate to the rotationalspeed of the sprockets. Here, the sprock-et diameters are shown with the letter S.

Since the sprockets are physicallyattached to the same drive shaft as thewheel, the sprocket ratios can be equat-ed to the wheel diameter ratios as seenin Equation 5.

For this type of a robot drive systemto work properly, the sprocket ratiomust be the same as the wheel ratio.Sprockets are usually identified by thenumber of teeth they have instead oftheir actual diameters, so the letter Scan be substituted with the number ofteeth on the sprocket. The ratio will bebased upon the number of teeth oneach of the sprockets.

νν == ππ ΝΝ D Equation 1

νν == ππ ΝΝ11 D11 == ππΝΝ22 D22Equation 2

ΝΝ11 == —D22 ΝΝ22D11

ΝΝ11 == —s22 ΝΝ22s11

Equation 3

Equation 4

Figure 1. Illustration of a two wheel drive system with different diameter wheels.

ASK Mr. Roboto

Tap into the sum of all human knowledge and get your questions answered here! From softwarealgorithms to material selection, Mr. Roboto strives to meet you where you are. And what morewould you expect from a complex service droid?

[email protected] Our resident expert on all things robotic, is merely an Email away.

by Pete Miles

SERVO 11.2003 21

roboto.qxd 10/9/2003 1:53 PM Page 21

The challenge to making a robotlike this work properly is finding theright combination of sprockets and

wheels that will have the same ratios.Depending on the sizes of the wheelsyou want to use, you may have tobuild a sprocket and chain based gearbox between your front and rearwheels so that you can use the samemotor to drive both wheels with thesame linear velocity.

Q.I am new to robotics and Iwould like to get into it.What I would like to do is

take a car (full size automobile) andmake it radio controlled. I would mostlikely start with lawn mowers and go-karts. Now, I don't really know whereto start, but I am guessing the RobotBuilder's Sourcebook would be good.Could you point me in some direction?

— Joseph Whitneyvia Email

A.The Robot Builder's Source-book by Gordon McCombfrom McGraw-Hill is probably

the best single source for finding justabout anything you would need tobuild a robot, but you are going toneed to know what to do with theparts in order to build the radio con-trolled automobile.

This may sound silly, but the radiocontrolled gasoline cars you can get atthe hobby store will show you how toget started. Most of the technologythat makes the car radio controlled willbe very similar to what you will needto do to make the automobile radiocontrolled. They are the best place toget started, and taking them apartand modifying them to work better iswhere you will learn a lot about howto remotely control an automobile.

The three most important thingsyou need to keep in mind when doingsomething like this is safety, safety,and safety. A 3,000 pound car cancause a lot of damage, or even death,

if a small mistake is made. A 100pound go-kart can also cause a signif-icant amount of damage if somethinggoes wrong. So starting small is theright way to get rolling.

Probably the two best places toget started with this type of a projectis either getting involved with yourlocal high school FIRST (For Inspirationand Recognition of Science andTechnology) team, or getting involvedwith building combat robots like theones shown on TV, such as RobotWars and BattleBots. Both of theseareas involve building large radio con-trolled robots with a heavy emphasison safety. And what you learn inbuilding them can be applied to build-ing the radio controlled automobile.

More information about FIRST canbe found at www.usfirst.org There isa lot of information about buildingcombat robots that can be found onthe Internet and there are severalbooks that have been published onthis topic. But the best place to learnabout combat robots is to actuallybuild them and participate in a localcontest. A good place to learn aboutthe many different combat robotevents is at the Robot FightingLeague's websitewww.botleague.com

By participating in either of theseactivities, you will learn how to buildthe mechanics, the electronics, andthe radio control systems to drivethese robots around, and all thisknowledge can then be applied tobuilding that radio controlled automo-bile.

Q.I am using an R/C servo tocreate linear motion butmy design prevents the

use of a rack and pinion setup. So, Iam using a standard servo horn with aball joint and some threaded rod. Theproblem is that the travel is uneven,being faster in the middle than at theends.

Is there a clever mechanism I canuse to "linearize" this motion? Or, sinceI am using a BX-24 to drive the servo,is there a quick way to do this in software?

— Anonymous via Internet

A.The rack and pinion and theball screw systems are two ofthe best ways to convert

rotary motion into uniform linearmotion. The linear position and velocityare uniformly proportional to the rota-tional position and velocity of the driveservo.

Another popular method is to usecams to move a sliding bar. Both posi-tion and velocity profiles as a functionof the servo motion can be tuned forlong uniform velocity motions with ashort and fast return motion. Two otherpopular methods for converting rotarymotion into linear motion are called thefour bar linkage and the slider crankmechanism. The advantage to the lat-ter two is that they are relatively easy toimplement (which is probably what youare using right now), but the drawbackis that the output velocity will follow asinusoidal pattern, which also soundslike what you are getting in your setup.

There are many clever kinematicmechanisms that can approximate a"linear" motion from a rotary motion.An excellent source for different typesof mechanisms is the four volume setIngenious Mechanisms by Jones andHorton. But since you have a designconstraint that does not allow a rackand pinion solution, you may not havethe room to implement one of theseclever kinematic solutions. Thus, youmay have to use an electronic and/orsoftware solution.

R/C servos make excellent servomotors when controlling position is themain goal. A servo is designed to moveat its maximum speed to get to its com-manded position, and they only slowdown when it gets very near the com-manded position. Controlling the veloc-

s22s11

Equation 5

==D11

— —D22

1 6

11

16

21

26

31

36

41

46

51

56

61

66

71

76

0

200

400

600

800

1000

1200

Figure 2. Servo position vs. timedue to a trapezoid velocity profile.

22 SERVO 11.2003

roboto.qxd 10/13/2003 2:21 PM Page 22

ity of a servo can be done if you com-mand the servo to make a series ofsmaller move increments instead of onelarge positional movement. Since stan-dard R/C servos require the commandedposition to be updated every 15 to 20ms, this can be used to our advantage.

For example, a common servo mayhave a speed rating of 60 degrees in 0.2seconds. This is the same as a six degreemovement in 20 ms. Now if you wantthe servo to move a total of 60 degrees,you can command the servo to movethe total amount in one command, andthen you will have to repeat this movecommand 10 times (10 x 20 ms = 0.2seconds), for the servo to complete thatmove.

Another way to do this is to createa program loop in your microcontroller

where you increment the commandedposition from six degrees to 60 degreesin six degree increments.

With the same 20 ms pausesbetween each of these move com-mands, you will still get the same totalnet move result in the same amount oftime. This represents the maximumvelocity move for this servo. You can'ttell it to go faster — but you can tell it togo slower.

Now if we changed the same loopto three degree steps, and still used thesame 20 ms time delay between eachcommanded move, the servo will ineffect move at half the speed as in theprevious example. This is because theservo will reach the three degree pointin about 10 ms, as the true velocity ofthe servo is still six degrees per 20 ms.

Thus, the servo will wait for 10 msat the three degree position, until thenext move commend is sent to theservo. If you use one degree incremen-tal steps, then the servo will move atabout 1/6th the maximum speed. Byadjusting the incremental move dis-tances, you can control the speed ofthe servo, as long as the desired speedis less than the maximum speed of theservo.

Now how does this fit in with yourproject? You can command the servoto move at a slower speed for its nor-mal operation — say, half its normalspeed. When you come up with situa-tions where you need to increase thespeed, use fewer and larger incremen-tal movements, and when you want togo slower, use more smaller incremen-tal movements.

The BASIC Stamp 2 is fully capableof doing this. You are going to have todo some experiments to get the rightmotion profile you want. You may haveto make a look-up table with the vari-ous incremental move commands tosimplify the programming of yourmicrocontroller.

The program in Listing 1 shows anexample of using a Lookup function togenerate a trapezoidal velocity profilewith a standard R/C servo. It is alsoshown graphically in Figure 2.Depending on how complex the veloc-ity and motion control profile youwant, you may want to use a dedicat-ed microcontroller to control the servo.

Listing 1

'$STAMP BS2 '$PBASIC 2.5

' Basic Stamp 2 program demonstrating' variable speed control of a Tower Hobbies' TS-53 standard servo, using a Lookup' function to coordinate the velocity and' position together.' This servo will move through the following' sequence:' Move to 0 Degrees at maximum speed, ~300' Deg/sec (60 Deg/0.2 sec)' Move from 0 to 24 Degrees at a constant' velocity 50 Deg/sec' Move from 24 to 66 Degrees at a constant' acceleration 1042 Deg/sec^2' Move from 66 to 114 Degrees at a constant' velocity 300 Deg/sec' Move from 114 to 156 Degrees at a constant' acceleration of -1042 Deg/sec^2' Move from 156 to 180 Degrees at a constant' velocity 50 Deg/sec

i VAR Word ' Counter VariableValue VAR Word ' Position value

Main:FOR i = 1 TO 60 ' Move to start position

PULSOUT 1, 400PAUSE 20

NEXT

FOR i = 0 TO 80 ' Through its pacesLOOKUP i,

[403,407,411,415,419,423,427,431,435,438,442,446,450,454,458,462,466,470,473,477,481,485,489,493,498,504,512,521,533,545,560,576,593,613,634,656,680,703,726,750,773,796,820,843,865,886,906,923,939,954,966,978,987,995,1001,1006,1010,1014,1018,1022,1026,1030,1033,1037,1041,1045,1049,1053,1057,1061,1065,1068,1072,1076,1080,1084,1088,1092,1096,1100], Value

PULSOUT 1, Value ' Each period = 2usPAUSE 20

NEXTGOTO Main ' Restart the motion sequence

END

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23

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Circle #125 on the Reader Service Card.

roboto.qxd 10/13/2003 2:21 PM Page 23

The world is an ocean of parts. Junkyards and hard-

ware stores stand among the dozens of spawning

grounds for your next creation. But finding 'bot

construction materials is not as head spinning as knowing

what to look for.

Shakes WWalker

“Shakes,” a three-servo hexapod walker, handsculpted and soldered together out of copperplated TIG welding rod.

by David [email protected]

GeerHead

24 SERVO 11.2003

Testing YYour MMetal

Geer.qxd 10/10/2003 6:20 AM Page 24

Steels, plastics, brass and copper,bronze, aluminum, woods, and com-posites — these are the best. Factorslike availability, cost, strength, andease of use will influence your choice.“Availability and ease of use are themost crucial,” says Roger G.Gilbertson, President of Mondo-tron-ics, Inc., and The Robot Store.

Proto Parts Primer

Want a 'bot to be proud of? Makeyour mistakes on a prototype first.

Some materials are specially suit-ed to prototypes. Polyvinyl chloride(PVC) and plywood are cheap, easy tofind, and easy to work. Plywood boxesand I-beams are very strong and have

a good weight-to-strength ratio. “PVC is relatively heavy, not as

strong, and deforms, but it's useful inprototyping chassis and support struc-tures,” says Dr. Alan N. Federman, asenior NASA engineer. Aluminumextrusion is pricey, but very boss forprotos.

It can be worked like a giant erec-tor set. Cardboard, foamcore, andStyrofoam help with correct sizing andproto-making.

Heavy Metal Rave —on the Mild Side

Mild steel is common in cars andappliances. Useful in many areas ofrobotics, it's a favorite for low budg-

ets. It has moderate strength, weldseasily, and machines well, too. Mildsteel specs into the neighborhood ofa 1015. (The 15 tells you how muchcarbon it has, says H. Ben Brown, Jr.,Project Scientist, The RoboticsInstitute, Carnegie-Mellon University.)As carbon content increases, so doesstrength, but at the expense of work-ability. "Take a walk on the mild side"when strength is less important thancost. Parts like fasteners come in mildsteel (also in high strength steels, alu-minums, and even titanium).

High Carbon

High carbon steels are in the vicin-ity of a 1030 or 1040 (see AlloyInfoReports at All Metals & ForgeInformation Resources, free registra-tion required). The more carbon, themore heat treatable and the harder itis. It can be precast or you can shapeit yourself.

Music wire (piano wire) — madeof hardened high carbon steel — isavailable in several diameters. Pianowire is good where you need a hardsteel rod.

Drill rod works well where youneed a shaft of a precise diameter anda certain hardness. Dowel pins arealso examples of very hard steel inexact sizes, though in shorter lengths.

Chromoly Alloys(Chrome Moly)

Chromoly is a steel alloyed

FIRST TTeam 2255Extruded aluminum is used for finalchassis construction. (2000) FIRSTNational Champion — Team 255, SanJose, CA.

Photo courtesy of Dr. Alan N. Federman, NASA.

SERVO 11.2003 25

Geer.qxd 10/8/2003 6:02 PM Page 25

(mixed) with molybdenum and chromi-um. Chromoly tubing can be weldedinto strong, light frames. As with race-cars, it's good for robots that will bedoing some traveling (under their ownpower).

Other Steel Formats

“For robots that need to be lightand strong, I like TIG rod (steel rodscoated with copper used for welding).These are inexpensive, strong, and youcan solder them together with aplumbing-soldering gun. It's easy toget really creative!” says Mr.Gilbertson.

Suppliers

Places to locate these and otherparts and materials include McMaster-Carr, All Metals and Forge, the HumanPower Source Guide, surplus outlets,and hardware stores.

The Wrap on Plastics

High Density Polyethylene (HDPE)resists impact, corrosion, and abra-sion. Polycarbonate resists impact andis good for structural and gearboxhousings. Acrylic can be used foroptics and can be made impact resist-ant. Delrin is strong, chemical resist-ant, and has low moisture absorption.It's used for bushings and bearings.Nylon absorbs moisture.

“I use some plastics, like poly-styrene, ABS, and PVC. I use lots of

found parts and adapt them to newuses. For example, an ABS electricalbox cover plate can become the basefor a robot,” says John Kittelsrud,President, PAReX (Phoenix AreaRobotics eXperimenters).

Suppliers abound on the Internet— Tap Plastics, Lowes, Menards, andGE Plastics are good places to startlooking. Sheet plastic can be had fromplastics dealers and hobby shops.

Brass, Copper, andBronze

Brass machines and solders well.Its moderate strength is comparable tomild steel, though it is denser and notas stiff. "There is a property calledYoung's Modulous (the modulous ofelasticity) that tells you the stiffness ofthe material as differentiated from itsstrength. This tells you how much itwill deflect under a certain load," saysMr. Brown. For parts where strength isnot as important as machining andsoldering, brass is worth considering,as well.

Copper is good for electrical andthermal conductivity. It's used forwiring and can be easily soldered.Phosphor bronzes are used in springswhere toughness and elasticity arerequired.

Aluminum Alloys

Aluminum alloys can be heat-treated to varying hardness. 6061 T-6is a very good general-purpose alloy. It

machines pretty well and can be weld-ed. It's available in many shapes likebar stock, beams, channels, and flatsheets. “That's what we use most gen-erally,” says Mr. Brown.

7075 T-6 is stronger than 6061due to the additional alloying compo-nents: copper, zinc, and titanium. TheRobotics Institute uses that to meethigh strength requirements. It's moreexpensive and not available in as manyform factors.

Alloy 2024 T-4 has a strength75% greater than 6061. "There's anumber called yield strength that'simportant. That's the stress level atwhich the material permanentlydeforms. You usually want to stay wellbelow that," says Mr. Brown. Alloy2024 has a 47 kPSI (thousands ofpounds per square inch) yieldstrength. The 6061 T-6 is 40 kPSI andthe 7075 is 73 kPSI. All aluminums willhave about the same weight or stiff-ness, but differing strengths.

Steel is about three times asdense as aluminum and about threetimes as stiff. Though the two metalsseem equal in this respect, aluminumis often the better choice. Given twolarge structures of the same weight,an aluminum one can be stiffer thansteel.

Carbon Fiber

Among Kevlar, carbon fiber, andfiberglass, carbon has the highest stiff-ness-to-weight ratio, and a fairly highstrength-to-weight ratio. With com-

The GGyroverGyrover is a gyroscopically stabilized, single-wheelrobot built inside a 16” lightweight bicycle wheel.The domes on each side are made of polycarbonatesheet which provides transparency with goodstrength and impact resistance. The main platform isfabricated from a sandwich structure of two layers of1/16” aircraft plywood with balsa wood between —this is lightweight and strong, and allows easymounting of components. Other major mechanicalparts are of 6061-T6 aluminum, which has goodstrength, and is low in cost and easy to fabricate.

Photo courtesy of "The Robotics Institute, CarnegieMellon University."

26 SERVO 11.2003

Geer.qxd 10/8/2003 6:03 PM Page 26

posite materials, you can direct thefibers according to where you wantthe strength. For example, if you wanta beam to resist bending, you'll wantthe fibers aligned lengthwise.

Fiberglass is of lower cost, lowerstrength, and not surprisingly, morefrequently used. Kevlar, on the otherhand, is as strong but not as stiff ascarbon. You can buy composite mate-rials in rods, square bar, or sheet stock.You can also buy raw fibers or clothand add the resin yourself to cure itinto a structure of your choice.

Wood

“Wood is low in cost and density,light in weight, and easy to cut anddrill. It's something we use a lot forlarger structures,” says Mr. Brown.Spruce — once used in small aircraft —is good for structures. Pine is also agood structural material. Plywood —layers of wood laminated so the grainsare at different angles for strength —is good for stable construction thatwon't warp.

“Plywood (1/2-inch thick birch) isa great prototyping material,” says Dr.Federman. Light and easy to machine,it can be formed into I-beams or boxes

with glue, hand tools, and drywallscrews. “Plywood is a sophisticated,laminated wood product that can alsobe used to add strength to sheetmetal components,” says Dr.Federman.

According to Mr. Kittelsrud,hobby packs of pre-cut 1/4-inch x1/4-inch hardwoods (available athobby stores) are great to work with(think “wooden LEGOS”). “I usethem because I don't have a big shopto rip lumber down to smallerpieces,” says Mr. Kittelsrud. These arehandy for body frames and mountsfor electronics.

Extra SStuff, NNotes,and PPointers

Additional MaterialsSources

Check the computer junkyard formodular steel and aluminum shelvingunits with pre-drilled L and squarebeams. A hacksaw will do for cuttingthem to size. The Home Depot alsocarries myriad construction materialson the cheap — electrical conduittubes, aluminum fence posts, and

steel hardware.

Don't Dive in Empty-handed

“You don't have to have a full-onComputer Numerically Controlled(CNC) mill set up at home or a degreein mechanical engineering to build arobot,” says Mr. Kittelsrud. Smallpower tools and hand tools will bringmost materials into submission.

A drill press and power sander arerecommended for large or heavywoods and plastics. “If you use steelor heavy aluminum, you will needsome serious metal working equip-ment — a mill, lathe, welder, cutters,and bits,” says Mr. Gilbertson.

Do Most HomeRoboticists Prefer RawMaterials to Kits?

“This is a darn good question. Inall of the contests I have been to, thescratch-builts have always outnum-bered the kits. I think it's part of thewhole DIY robot thing,” says Mr.Kittelsrud. Precast parts that just gotogether are often too easy, likepainting by numbers.

Killer BBee

Killer Bee, 500-gram mini sumorobot.

Photo courtesy of John Kittelsrud.

SERVO 11.2003 27

S

Resources

Geer.qxd 10/8/2003 6:03 PM Page 27

Orb oof DDoom

“The Orb of Doom” is a radio-controlled “hamsterball” robot with a shell of carbon-Kevlar over afoam core form. It met its own, personal doom atthe Second Robot Wars event in 1995.

Photo courtesy of Roger G Gilbertson,RobotStore.com

Millibot TTrainThe Millibot Train combines multiple, tracked modules intoa single train, with articulated joints for enhanced mobility.This working model uses the Fusion Deposition Modeling(FDM) rapid prototyping method for fabrication of its majorparts. FDM allows fast, low-cost fabrication of plastic parts,moderate dimensional resolution (~.010”), and productionof parts — such as the hollow-core sprockets for the tracks— that could not be made by conventional machining. Otherparts include standard hobby servos to drive the tracks,music wire axles, and tubular brass, plus small toothed beltsto make the tracks.

Photo courtesy of The Advanced Mechatronics Lab,Carnegie Mellon University.

The RRobot SStorewww.robotstore.com

Alloy IInfo RReports, AAll MMetals & ForgeInformation RResourceswww.steelforge.com/infoservices/infoservices.asp

McMaster-Carrwww.mcmaster.com

The HHuman PPower SSource GGuidewww.ihpva.org/SourceGuide

Tap PPlastics www.tapplastics.com

Loweswww.lowes.com

Menardswww.menards.com/nindex.html

GE PPlasticswww.geplastics.com

The HHome DDepotwww.homedepot.com

28 SERVO 11.2003

Resources

Geer.qxd 10/8/2003 6:08 PM Page 28

75 MHz INCU BusR. Kieronski, Newport, RI

Send us a high-res picture of your robot with a fewdescriptive sentences and we'll make you famous.Well, mostly. [email protected]

Gliding slowly along the floor,its lighted eyes cast a patternon the wall in the direction ofits video camera gaze.Maneuvered by the operatorthrough a radio link. If you arechosen, it will squirt you withits finger.

It is as a metaphor for theinformation systems that silent-ly exercise their surveillancepowers on us ... at least youcan see this one.

www.lumion.net

Green Eye Silver DragonSuni Murata, Somewhere in CA

Thirty pound fighting robot made of sheetaluminum and fast electric motors. Willsport a pneumatic flipping tail in thefuture. My basic philosophy: Learn fromeveryone else and incorporate the designthat works. [email protected]

GTRBOT666JBOT, San Francisco, CA

This electric guitarplaying robot from theband Captured! ByRobots! is over sevenfeet tall, weighs 130pounds, and reported-ly rocks harder thanyou.

www.capturedbyrobots.com

DexterSteve Benkovick, Northridge, CA

Built to compete in the 10 foot squareIEEE MicroMouse maze, Dexter has a68HC11 brain and 32K of RAM. It is pro-pelled by unipolar steppers, powered by10 NiMH batteries and uses five IR sensorson each side to detect walls within themaze.

www.micromouseinfo.com

SERVO 11.2003 29

menagerie.qxd 10/13/2003 2:25 PM Page 29

Multi-Position Chargers

Cell-Con Incorporatedannounces the

availability of its cus-tom, multi-positionchargers. Multi-positionchargers are availablefor simultaneouscharging of multiplebattery packs assembledfrom one of the following chemistries:lithium ion, NiMH, NiCd, or sealed lead acid.

These chargers are based on existing designs andtechnology that is easily adaptable to specific customerrequirements. Fast project turn around time (30-180 days)and a minimal financial investment are typical. Small andlarge volumes accepted.

Customer specified options such as charging method(constant current/constant voltage, smart, constant cur-rent, overnight, and float), open frame, and batteryrefresh capabilities are available.

Prices range from a few hundred dollars to a fewthousand dollars depending upon the complexity of thecharger and its volume.

Cell-Con Incorporated is a US-based manufacturer ofcustom power systems consisting of single position charg-

ers, multiposition chargers, custom battery assemblies,power supplies, and analyzers.

For further information, please contact:

Servio™ — The New R/C Servo andI/O Slave Controller

PicoBytes, Inc., a leadinginnovator of robotics and

automation controllers, hasreleased its new serial R/Cservo and I/O slave controller— Servio™ . It is an intelligentserial R/C servo and I/O slavecontroller capable of control-ling up to 20 R/C servos with 16-bit resolution and 256-speed settings. It also has eight A/D converter ports capa-ble of 10-bit resolution at 40 samples/second, with twoPWM signal generators capable of up to 10-bit resolutionwith direction control for H-Bridge connections and two-

New Products

ACCESSORIES

CONTROLLERS & PROCESSORS

NNeeww PPrroodduucc ttss

305 Commerce Dr., #300Exton, PA 19341

Tel: 610•280•7630Fax: 610•280•7685

Email: [email protected]: www.cell-con.com

Cell-Con Incorporated

30 SERVO 11.2003 Circle #109 on the Reader Service Card.

Circle #111 on the Reader Service Card.

NovNewProducts.qxd 10/8/2003 11:44 AM Page 30

channel R/C decoder with differential steering override.Unused A/D and servo ports can be configured as digitalI/O.

Powerful features such as monitoring, servo sweep,and sequence functions offload the burden of constantpolling and control from the master CPU. Unlike otherproducts, there are no complicated languages to learn. Allthis power is available by sending simple serial commandat rates of up to 115,200 bps, which can be accomplishedwith any computer or MCU.

A comprehensive user and technical manual explainsall aspects of operation with many code examples.

Servio consumes less than 14 mA and weighs only0.8 ounces (22 grams) in a 2.5" x 2.5" (63mm x 63mm)footprint, which makes it ideal for battery and mobileoperations.

For further information, please contact:

SM3416SmartMotor™ — A

NEMA 34 Size Low-Cost Integrated

Servo Motor

Animatics has launched theSM3416, NEMA 34 size low

cost integrated servo motor. The

SM3416 is exceptional, producing more than 1 NM oftorque at an unprecedented low cost.

Those who love the benefits of integrated servomotors have been clamoring for a low cost product in theNEMA 34 size and torque range. While it sets a new prece-dent in low cost integrated motion control, the SM3416has all the features you've come to expect fromSmartMotors — a true departure from the wiry mess ofthe traditional component solutions.

In 1994, when Animatics released the world's first lineof fully integrated servos, with all of the positioning elec-tronics, driver circuits, and the encoder built into a singlesmall unit, the industry was slow to accept the radicaldeparture from conventional motion control. Today, thatfear is gone, the technology is proven, and the integratedservo market is touted by independent studies as thefastest growing market within the motion control industry.

The SM3416 is a SmartMotor in a familiar package.Based on Animatics' patented, award winning design, theSM3416 is the final chapter of the highly successful line ofOEM series SmartMotors. Comprised of both NEMA 23and NEMA 34 size SmartMotors, the OEM Series deliverscompetitively priced integrated motion control to the highvolume OEM and integrated markets.

Animatics Corporation is the world leader in integrat-ed motion control. Animatics is located in the heart ofSilicon Valley and designs, manufactures, and marketsmotion control products for industries ranging from semi-conductor, nuclear, automotive, and machine tool to tradi-tional industries such as CNC. Animatics' strength lies inusing technological innovation to meet complete solutionsfor motion control. For further information, please contact:

New Products

10674 Chinon Cir.San Diego, CA 92126

Tel: 858•549•7394 Fax: 858•581•3375Email: [email protected]

Website: www.picobytes.com

PicoBytes, Incorporated

MOTORS

3050 Tasman Dr.Santa Clara, CA 95054Tel: 408•748•8721

Email: [email protected]: www.animatics.com

Animatics Corporation

NPC Robotics, Inc. •4851 Shoreline Drive • PO Box 118 • Mound MN • 55364 • 800-444-3528 • Fax: 800-323-4445 • E-mail: [email protected]

Check Out

Our Website!

www.npcrobotics.com

SERVO 11.2003 31

Circle #112 on the Reader Service Card.

Circle #113 on the Reader Service Card.

NovNewProducts.qxd 10/8/2003 11:44 AM Page 31

Hexapod Walker Kit

Lynxmotion has introduced theirtotally redesigned Hexapod

1 Walker kit. This walker usesthe traditional three servodesign with a twist.Lynxmotion has implemented a paral-lelogram on the lifting legs to eliminatefriction. This makes the walker much moreefficient than other designs. The walker ismade from precision laser-cut Lexan (polycarbonate) mate-rial. The assembly is easy using common hand tools. Theall “nuts and bolts” construction means there is no glue ortape. All of the legs are actuated by quality ball links forreliable operation. The kit uses powerful Hitec HS-422 ser-vos. There are optional "punch-outs" to add either a stan-dard or a micro-size servo to the front. This makes addinga pan and tilt camera mount or panning ultrasonic sensorvery easy. The chassis will accept either our Next Step car-rier or an OOPic-R microcontroller. The Next Step can usethe BS-2, the BASIC Atom, or the OOPic-C microcontroller.The microcontroller can be mounted on top the robot, orinside to provide room for additional peripherals.

The robot is available as a bare chassis (including ser-vos) for those who want to roll their own electronics. It isalso available in several combo kits which include everythingneeded to get the robot up and running right away. Withthe addition of the optional “Pan & Tilt” camera mount, aHitec remote control set, and a camera and video transmit-ter, the robot can be configured as a remote piloted rover.Prices start at $99.95 for a truly affordable robot experimen-tation platform. Stop by the Lynxmotion website to see theassembly guide, video of the robot in action, and muchmore. For further information, please contact:

WEASEL — A Touching andSeeing Robot Kit

OWI introduces the Weasel —a tenacious little robot

warrior that embodies twosensors that allow it to "see" aline or "feel" its way alongwalls and around corners. The two motors and contactsensor activate the wall sensing micro switch to controlthe motor’s on/off operation that determines the path ofa wall. It is the classic robot design using the "Left HandRule" to escape mazes.

With OWI's continued pursuit in making robots"smart," they have added an additional feature to this littlebundle of energy … a sonic tracking system. BeneathWeasel's sturdy plastic base, you will discover photo-transistors that enable it to detect and follow a black line.The Weasel also boasts a three-speed gearbox which willhelp navigate at the velocity you determine. Quick andeasy to assemble, this is a beginner robot that makes greatentries for robotic competitions, robotic workshops, after-school programs, special events, gifts, science enrichmentcamps, and classroom activities. It has a suggested sellingprice of $24.95. For further information, please contact:

New Products

PO Box 818Pekin, IL 61555

Tel: 866•512•1024 Fax: 309•382•1254

Email: [email protected]: www.lynxmotion.com

LynxmotionIncorporated

17141 Kingsview Ave.Carson, CA 90746

Tel: 310•515•1900 Fax: 310•515•1606Email: [email protected]

Website: www.robotikitsdirect.com

OWI Incorporated

32 SERVO 11.2003

How much damage can one pound do?

WWW.SOZBOTS.COM

sixteen oz fighting robots

Specializing in antweight robotic combat parts.

Circle #117 on the Reader Service Card.

ROBOT KITS

Circle #114 on the Reader Service Card.

Circle #115 on the Reader Service Card.

NovNewProducts.qxd 10/8/2003 11:45 AM Page 32

Programming Robot Controllersby Myke Predko

In this innovative addition tothe Robot DNA Series,author Myke Predko demon-strates how robot controllersare programmed using theversatile Microchip PICmicroMicrocontroller. The focus ofthe book is on the leastunderstood aspect of robotdesign: integrating multiple sensors andperipherals software that will work coopera-tively and allow for a simple high-level con-trol application. To explain the concepts pre-sented in the book, Myke uses off-the-shelfparts and a “C” programming language com-piler that is included on the CD-ROM. $24.95

Robot Mechanisms andMechanical Devices Illustrated

by Paul SandinBoth hobbyists and profes-sionals will treasure thisunique and distinctivesourcebook — the mostthorough and thoroughlyexplained — compendiumof robot mechanisms anddevices ever assembled.Written and illustrated specifically for peoplefascinated with mobile robots, RobotMechanisms and Mechanical DevicesIllustrated offers a one-stop source for every-thing needed for the mechanical design ofstate-of-the-art mobile ‘bots. $39.95

Anatomy of a Robotby Charles Bergren

This work looks under thehood of all robotic proj-ects, stimulating teachers,students, and hobbyists tolearn more about thegamut of areas associatedwith control systems androbotics. It offers a uniquepresentation in providing both theory andphilosophy in a technical yet entertainingway. $29.95

Building Robot Drive Trainsby Dennis Clark / Michael Owings

This essential title inMcGraw-Hill’s Robot DNASeries is just what roboticshobbyists need to build aneffective drive train usinginexpensive, off-the-shelfparts. Leaving heavy-duty“tech speak” behind, theauthors focus on the actualconcepts and applications necessary tobuild — and understand — these critical force-conveying systems. If you’re hooked on amateur robotics and want a clear, straight-forward guide to the nuts-and-bolts of drivetrains, this is the way to go. $24.95

Constructing Robot Basesby Gordon McComb

Here is the first title in theinnovative new Robot DNASeries from McGraw-Hill,the premiere publisher ofreferences for the roboticshobbyist. Author GordonMcComb focuses on thebasic concepts and specif-ic applications you need tobuild efficient robot bases – and have agreat time in the process. In the clear, easy-to-follow style that has made him a favoriteamong robotics fans, Gordon tells you howto get things up and running using only inex-pensive, easily-obtained parts and simpletesting equipment. Detailed enough to getthe job done, but written with the amateurhobbyist in mind, Constructing Robot Basesis your first point of reference when design-ing and building this essential subsystem.$24.95

PIC Robotics: A Beginner'sGuide to Robotics Projects

Using the PIC Microby John Iovine

Here’s everything therobotics hobbyist needsto harness the power ofthe PICMicro MCU!In this heavily-illustratedresource, author JohnIovine provides plans andcomplete parts lists for 11easy-to-build robots each with a PICMicrobrain. The expertly written coverage of thePIC Basic Computer makes programming asnap — and lots of fun. $19.95

Applied Robotics IIby Edwin Wise

Instructive illustrations,schematics, part numbersand sources are also pro-vided, making this booka “must” for advancedbuilders with a keeninterest in moving fromsimple reflexes toautonomous, AI-basedrobots. Create larger and more useful mobilerobots! Ideal for serious hobbyists, AppliedRobotics II begins by discussing PMDC motoroperation and criteria for selecting drive, arm,hand and neck motors. $41.95

We accept VISA, MC, AMEX, DISCOVERPrices do not include shipping and

may be subject to change.

The SERVO Bookstore

CNC Roboticsby Geoff Williams

Now for the first time youcan get complete direc-tions for building a CNCworkshop bot for a totalcost of around $1,500.00!CNC Robotics gives youstep-by-step, illustrateddirections for designing,constructing, and testing afully functional CNC robot that saves you 80percent of the price of an off-the-shelf bot —and that can be customized to suit your pur-poses exactly, because you designed it.$34.95

Concise Encyclopedia ofRobotics

by Stan GibiliscoThis handy collection ofstraightforward, to-the-point definitions is exactlywhat robotics and artificialintelligence hobbyistsneed to get and stay up tospeed with all new termsthat have recentlyemerged in robotics andartificial intelligence.Written by an award-winning electronicsauthor, the Concise Encyclopedia ofRobotics delivers 400 up-to-date, easy-to-read definitions that make even complexconcepts understandable. Over 150 illustra-tions make the information accessible at aglance and extensive cross-referencing and acomprehensive bibliography facilitate furtherresearch. $19.95

JunkBots, Bugbots, and Bots onWheels: Building Simple Robots

With BEAM Technologyby David Hrynkiw / Mark Tilden

Ever wonder what to dowith those discarded itemsin your junk drawer? Nowyou can use electronicparts from old Walkmans,spare remote controls,even paper clips to buildyour very ownautonomous robots and gizmos. Get step-by-step instructions from the Junkbot mas-ters for creating simple and fun self-guidingrobots safely and easily using common andnot-so-common objects from around thehouse. Using BEAM technology, ordinarytools, salvaged electronic bits, and the occa-sional dead toy, construct a solar-poweredobstacle-avoiding device, a mini-sumo-wrestling robot, a motorized walking robotbug, and more. Grab your screwdriver andjoin the robot-building revolution! $24.99

To order call 1-800-783-4624 or go to our website at www.servomagazine.com

SERVO 11.2003 33

Mind CandyFor Today’sRoboticist

BookstoreNov03.qxd 10/9/2003 9:14 AM Page 33

Sensing a sound with a robot ormicrocontroller can be challeng-ing. If one or more of the

sounds in question is relatively brief,the microcontroller must suspendother activities and spend it's timewaiting for the sound to occur. This can lock up the microcontroller

in a non-productive polling activity orelse risk missing the pulse by doingsomething else and then getting backto the sound input.

I present a circuit that offloadssome of the processing work to ananalog detector with persistentmemory.

A common task involving soundis to look for an average sound

level in a particular environ-ment. If only instantaneousvalues are available to thecomputer, some form ofdata storage and averagingmust be carried out.

Using a sound sensorwith the capabilities tostretch pulses and to sense

average sound levels canrelieve these tasks.

by Paul Badger

Art by Bryce Kho

TThhiiss MMoonntthh’’ssPPrroojjeeccttss

Low Cost Sound Sensor . 34

Battery Fuel Gauge . . . . . 38

Hexatron Part 1 . . . . . . . 42

SOZBOTS Part 2 . . . . . . 52

The Tracker . . . . . . . . . . 56

soundsensor.qxd 10/8/2003 3:16 PM Page 34

SERVO 11.2003 35

This small sound sensor — whichruns on 3-15 volts and features bothanalog and digital outputs — wasdesigned for my classes in physical com-puting at an art school. It introduces stu-dents to the usefulness of op-amps andillustrates several op-amp configurations.My students have found many uses forthe sensor including directly driving highefficiency LEGO motors, controllingsound activated sculptures, sound-mod-ulated lighting projects, as well as soundinputs for microcontrollers and robots.

How it Works

The sensor uses a cheap electretmicrophone element to sense and ampli-fy sounds. This signal is then rectified bya peak detector which converts thesound signal into a ground referencedDC voltage, holds this signal, and thenlets it sink back to ground level as slow-ly as desired.

A quad op-amp does all the signalprocessing. The first two op-amps areused to amplify and find the peak of theaudio signal. The third op-amp buffersthe voltage across the holding capacitorand supplies an analog output signal.The final op-amp is used as a compara-tor to produce a digital on/off outputsignal from the smoothly varying analogsignal.

Many of the sound sensor circuits Ihave seen using a single op-amp toamplify microphone signals are less thanoptimal because the open-loop gain ofmost op-amps is just barely adequate toamplify an audio signal from standardelectret microphone elements to a use-ful level. I have chosen to provide threestages to insure that there is enoughgain (audio sensitivity) for even the soft-est signals. Now whether your microcon-troller can be programmed well enough

to pull the softest signals out of thenoise is another story.

The Gory Details

Referring to the left side of Figure 1,U1 is an optional 78L05 regulator. Whena signal is being amplified by a factor of100,000 it only takes a small noise com-ponent in a power supply line to serious-ly degrade the desired signal. DC moto sare often the prime offenders in thisregard with their brushes, inductiveloads, and heavy current draw, which

often seem to radiate low level grungeback along the power lines. One of thebest ways to deal with this noise is toprovide a separate battery or power sup-ply. (Don't forget to tie the groundstogether at a "star" point.) This is notalways practical so a local regulator withbypass capacitors is another cheap andeffective cure.

If you don't use the regulator, justjumper the input pad to the output padon the board and omit C1. There is alsoan advantage in not using the regulator,

in that you can easily re-purpose the sen-sor for a higher voltage output if a lowervoltage regulator is on the board. Themicrophone element can be any inex-pensive electret microphone element. Ihad originally used a higher gain threelead mic that I found at HosfeltElectronics. Just jumper the positive andsignal pads for the more common twolead types. R1 and the zener voltage ref-erence IC lock the microphone bias to2.5 volts. This IC can easily be replacedby a 3 to 9 volt zener if you have one onhand. Besides providing a noise-freesupply to the mic, the zener's other jobis to keep the mic voltage below 10volts, in case a higher supply voltage isbeing used.

The voltage at the non-invertinginput of A1 (pin 12), is set by R2 and R4at slightly above the negative rail andalso serves as the reference voltage foramplifiers A2 and A3. The capacitorsacross the microphone bias voltagedivider (C8) and the reference voltagedivider (C9) are bypass capacitors thatform low pass filters. Again, the goal isto prevent variations in the power sup-ply from appearing as a signal. The elec-tret microphone's signal is coupledthrough capacitor C1 into the invertinginput of op-amp A1, that is set up as aninverting amplifier, the gain of which isset by the input and feedback resistorsby the formula: Gain = Rf / Rin. A slightcomplication here is that the input resis-tor is made up of R3 plus any resistancethat is to the "left" (in the sense of theschematic not the actual part) of thepotentiometer wiper. The feedbackresistance is made up of any resistanceto the "right" of the pot wiper. This ratiosets the maximum gain at 250K/2K =125 and the minimum gain at the lowerlimit of the pot, essentially zero, allow-ing the pot to have a larger control

Figure 1

soundsensor.qxd 10/8/2003 3:41 PM Page 35

range than if it had just been used as thefeedback resistor. By the way, only aninverting op-amp configuration can beused to reduce a signal in this waybecause the non-inverting configura-tion's minimum gain is one (unity).

C6, similar to C4, acts to pass theAC signal while blocking any DC bias.Both C6 and C4 also act as mild high-pass filters, so if you wanted the sensorto favor higher frequencies, you couldexperiment with smaller capacitor val-ues. The math for the corner (-3dB) fre-quency is supposed to be F =159,000/R6 * C6 (with C6 in micro-farads). A2 is also set up as an invertingamplifier with a gain equal to Rf/Rin =R7/R6 = 1,000. Diode D2, R8 and C9,and the Q1 network form a peak detec-tor circuit. Diode D2 charges C9 throughresistor R8 and prevents it from discharg-ing when the voltage falls beneath thepeak. With the MOSFET biased off, thecapacitor discharge times can be as longas 45 seconds. For longer times, use alarger capacitor, at the expense of aslightly less accurate response, as the op-amp has a finite ability to quickly chargelarger capacitors.

R9 also limits the response of thepeak detector and can be increased toyield a smoother charge curve. Thisallows the peak detector to functionmore as an average sound level detectorbecause brief pulses will tend to be gonebefore the peak-hold capacitor can fullycharge but more sustained sounds willeventually charge the capacitor. When Ibuilt the circuit, I cut off two positions ofan IC socket to mount R8 and C9, whichallowed me to easily experiment with dif-ferent timing constants. R9 should be200 ohms minimum. The MOSFET Q1,along with R10-R12 and D3-D6, com-

prise a network that bleeds the chargeon C9, controlling the speed with whichthe voltage on C9 returns to groundafter experiencing a transien t such as aloud noise. The remaining componentsin the network bias the outside legs ofpot R11 at about 2.4 vold and 1.6 volts,which comprise the full-on (for our pur-poses) and full-off points of Q1. Thewiper goes to the gate of Q1 controllingthe resistance of the MOSFET. AmplifierA3 is configured as a non-inverting

amplifier whose gain is set by resistorsR9 and R14 by the slightly differentequation: Gain = 1 + Rf/Rin = 1 +R14/R9 = 11. This gain helps boost eventhe weakest sounds to a full scale out-put. The non-inverting configuration ofA3 with its very high input impedancealso isolates the holding capacitor fromhigh current loads.

Amplifier A4 is configured as a com-parator with its output swinging fromfull high to full low when the pin 3 volt-age surpasses the reference voltage atthe inverting input (pin 2), which is setby the ratio of R14 to R19. SpecificallyVref = Vsupply * R19/(R14 + R19) and isan arbitrary (and non-critica) value that Ichose to be slightly above the “noisefloor” while viewing it on an oscillo-scope. Finally, the input and feedbackresistors R16 and R17 serve to give thecomparator some positive feedback tocreate hysteresis, which is a "snap" actionthat helps clean up noisy, borderline sig-nals. The ratio of R16 to R17 sets thehysteresis to 1/20. This creates a zone

36 SERVO 11.2003

Resistors Unless noted, all 1/4 W, 10%R1, R20 3 KR2, R15 47KR3 2 KR10, R16, R11 10 KR4 4 KR6 1 KR7, R14 1 MR8 1K, (see text), 200 Ω minimumR9 100 KR13 120 KR17 200 KR18, R19 5 KR5, R12 250 K trimpotCapacitorsC1 10 to 100 µF 25v tantalum or electrolytic (see text)C2 500 µF 25v electrolyticC3 10-100 µF 16v electrolyticC4, C6 - C8 0.1 µF 25v ceramic or monolithicC5 100 µF 25v mylar, polypropylene or monolithicSemiconductorsD1 LM385LP-2-5 2.5 vref (TO-92)D2 1N914 or 1N3595 low leakage diodeD3 - D6 1N914 (or equivalent)Q1 BS170 N-channel MOSFETU1 78L05 regulator (see text)U2 LMC6484 quad R/R op-amp or LM324 (see text)LED Any LEDMiscellaneousMic 2 or 3 lead electret microphone (Hosfelt MIKE-ET)Velleman DC Controlled Dimmer Kit (Jameco 128901)A double-sided plated-through PCB for the sound sensor is available for $10.00. It is not solder-masked or silk-screened. Please include either a SASE (preferred) or $1.00 for shipping.Contact Paul Badger, First Strike Graphics, 349 Morris Avenue, Providence, RI 02906.

Parts List

Figure 2

soundsensor.qxd 10/8/2003 3:17 PM Page 36

where the input signal can vary withoutswitching the output.

Odds and Ends

I have specified two different op-amps and each have pros and cons. TheLMC6484 op amp is a “rail-to-railinput/output” CMOS device whose inputsand outputs both include the supply rails,which is especially important with sensorsrunning in the 2 to 5 volt range. TheLM324 alternative is dirt cheap and ubiq-uitous, but can only swing its output towithin 1.5 volts of the positive supply rail.The LM324 also has about 20 milliampsmore output drive, which is useful if youplan to drive a small relay or motor direct-ly from the sensor.

Circuit Construction

The resistors and capacitors are allnon-critical, so don't hesitate to use slight-ly different values if you want to buildfrom parts on hand. This is a high gain cir-cuit so a printed circuit board with a largeground plane is recommended. It is cer-tainly possible to build the circuit on a perfboard with neat construction with theshortest practical leads being a good idea.There are numerous uses for the sensor,both on robots as well as in general gen-eral tinkering.The analog output of thesensor can be directly interfaced to aVelleman DC controlled light dimmer kit

to provide a cheap and easy sound-activated lighting system. When using a 5 volt input, the best results are obtainedby reducing the size of the optocouplerinput resistor.

The sensor can easily function as asound-operated motor control, either byusing the analog output with an emitterfollower transistor or by using the digitaloutput with a switching transistor (Figure2). With a microcontroller or BASICStamp, the sensor can provide input via anADC, or directly from the digital output toa microcontroller pin. Another idea that Ihave used in conjunction with microcon-trollers is to use a sensor as a kind of sonicmemory, so that the micro can hang outin a low power sleep cycle and once every10 seconds or so wake up and check tosee if anything is happening. If a high levelsound has been sensed then the microwakes up and does something.

When done, it resets the sensor byasserting a pin high that is wired to thebleeder MOSFET's gate and then sets thispin back to the high impedance “input”state. Another idea for using the sensor isin the area of frequency sensing — this willbe covered in a future article along withsome BASIC Stamp code examples.

An editable schematic is available onthe Servo website, www.servomaga-zine.com. I'll post any relevant revisions orreader feedback on my website atwww.paulbadger.org and you canreach me at [email protected]

SERVO 11.2003 37

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soundsensor.qxd 10/8/2003 3:18 PM Page 37

few tthings inelectronics seem so simple in appear-ance, yet in actual implementationsuch a difficult task, as the means todetermine the total available energy ina rechargeable battery.

Measure the battery voltage? Well,not quite. For starters, the measure-ment requires to be open-circuit volt-age — something that it is not feasiblein most applications. Then there is thefact that different battery chemistrieshave very different discharge charac-teristics. For instance, nicads have afairly flat voltage vs. charge character-istic, whereas lead-acid suffer a sub-stantial drop in voltage. Then there isthe temperature coefficient of thebattery voltage itself. The list goes onand on.

An accurate battery fuel gauge, asthese circuits are called in reference tothe familiar automotive gas gauges,are in reality quite challenging cir-cuits. These are usually customizedfor the application. As shown inPhoto 1, a commercial version ofthe circuit is fairly complex, andthus, it is no wonder that “smart”battery packs can cost $50.00 ormore. This particular device camefrom a camcorder, but cell phones,PDAs, and laptop computers have sim-ilarly complex devices.

On the other end of the spectrum,there are companies which make spe-cialized fuel gauge monitors. TexasInstruments offers a large portfolio ofdevices, which are very powerful andhave many features. But to operatethem properly, substantial engineer-

ing and programming effort isrequired.

One has to determine and programbattery coefficients like self dischargecharacteristics, temperature coeffi-cients, charge/discharge efficiencyratios, and other such things. This isway too much effort for a simple proj-ect. Still, if you are curious, visit theBattery Management link at theirwebsite, www.power.ti.com

I, however, was interested in a cir-cuit which would provide an improve-ment over the simple open circuit volt-age reading, without the complexity

and sophistication of the TI devices. In a battery, this means measuring

its charge, or amp-hours. Therefore,one would only require a current sam-pling resistor, an amplifier to convertthat miniscule resistor voltage to auseful level, then to a voltage to fre-quency converter, and finally to abunch of cascaded counters and a dis-play driver.

The result was a straightforward cir-cuit that was not very sophisticated,

but would work. One flaw was that itwould only measure battery dis-charge, such that the battery had tobe fully discharged and thenrecharged for the reading to be accu-rate. What if I wished to partiallycharge the battery, and then continuewith the discharge? You know, likeone always does with a vehicle, par-tially filling your fuel tank.

After some thinking, I came up witheven more circuit requirements: anabsolute value circuit previous to theV/F converter, a comparator to detectthe current polarity, a negative supplyto allow the operational amplifiers toswing to a negative voltage, counterswith up/down capabilities,overcoming their short countsequences, etc. Suddenly the circuitwas not simple anymore!

I built a prototype, but it just was notelegant. It did work, but it was way too

intricate. There must be a better way!I knew I could use a microcontrollerfor the up/down counters and thedisplay, but the rest of the circuitrywas still too complicated. Withoutany further recourse, I allowed the

project to whither for a while.Then I found a marvelous circuit from

Analog Devices. This device, designedto be a self contained watt-hour meter,has all the circuit functions that I wouldrequire. It amplifies and conditions thevoltage and current samples, multipliesthem, determines the resultant polari-ty, and converts it to a frequency pro-portional to watts — all with crystal-controlled digital accuracy and onlyrequiring a single positive supply. The

38 SERVO 11.2003

by Fernando Garcia IC software by Francisco Peña

battery fuel gauge

Photo 1Battery Pack

batteryfuelgage.qxd 10/8/2003 3:27 PM Page 38

pulses can then be fed to the microcon-troller, which will accumulate and dis-play them. This is the solution I waslooking for!

Of course, when one is countingwatt-hours, one is counting energy,whereas when one is counting amp-hours, one is counting charge — quite adifferent thing. The trick to make thething work is to feed in a very accuratevoltage, which then becomes justanother constant factor in the device'svoltage to frequency conversion ratio.By carefully selecting this factor andadjusting the count ratio by the micro-controller, I had achieved my intendedresult.

Circuit Description

As shown in the schematic of Figure1, the battery current is sampled with alow value shunt resistor, Rsh. More onhow to choose the value of Rsh later.After some filtering via R1, R2, C1, andC2, the voltage is applied to the currentsense input pins of U1.

The voltage sense inputs are “fooled”with a constant voltage developed bythe ratio of R4 to R9. An adjustablevoltage reference device, U2, is used tofeed both the divider resistor and U1'sreference voltage input. The voltage isadjusted to exactly 2.600 volts via P1,R7, and R8.

The device is crystal controlled forgreat accuracy. X1 is a common3.5795 MHz, “color burst” crystal, thesame frequency is used to drive themicroprocessor. After performing allthe internal computations digitally, U1then converts them to a variable fre-quency which is proportional to thecomputed value times a ratio of theclock frequency.

The value of this ratio is set digitallyvia pins S1 and S0. In this instance, thecircuit values and the frequency dividerare set such that 2,560 pulses are out-put, for a full-capacity battery dis-charge. This is what is known in batteryparlance as "1C" — one unit of batterycapacity. These pulses are then fedfrom U1's pin 24 to a port in the micro-controller, which counts them andadvances an LED every 256 pulses. U1'spin 22 is an output which produces afrequency 16 times faster than that ofpin 24. It is useful to monitor batteryactivity.

Another important signal comes outfrom U1's pin 20 to the microcontroller.It indicates the battery's current flowpolarity, or whether it is discharging orcharging. This is important because itnot only tells the microcontroller tocount down or to count up, but also,when counting up, that 320 pulses,instead of 256, are required to advancean LED count.

The reason for doing so is that it takesmore charging energy to recover whatwas lost during discharge. To accountfor that, we must have a longer countduring the charge period. I have experi-mentally determined that for a sealedlead-acid battery this amounts to abouta 25% loss, which more or less agreeswith the battery manufacturer's specifi-cation of 30%. Of course, you maychange this ratio easily by adjusting themicrocontroller's code. (Both the ASMsource code and the compiled HEXimage may be downloaded from theSERVO MAGAZINE website, www.servomagazine.com).

The display business of the project isa 10-LED bargraph, which is drivendirectly by the microprocessor, and cur-rent limited by resistor networks R11and R12. Each LED segment will lightup sequentially, as the battery ischarged or discharged.

If the supply voltage is interrupted,the battery state information could belost. Therefore, it is imperative that thelast state is stored in the microproces-sor's internal nonvolatile EEPROM.

Input port RB0 is configured as aninput which is flagged by the voltageregulator's reset output. In addition,this reset flag enables or disables Q1, aDarlington transistor. This feeds thepositive voltage to the LED display.When the reset flag is low, the transis-

Figure 1

SERVO 11.2003 39

batteryfuelgage.qxd 10/9/2003 7:04 AM Page 39

tor is disabled, and all of the LEDs willbe dark. This helps preserve currentsuch that the processor has enoughtime to perform the save state routine.

Finally, U3 provides a regulated +5volts for the project. It is a low-dropout device which will maintainregulation even in the most extremeconditions. Since it was designed forautomotive applications — wherereverse battery and voltage transientsare common occurrences — it hasextensive protection against mishaps.It also has a reset output, which isused for the purposes describedabove.

Circuit Construction

The circuit values shown in theschematic are useful for any lead-acid

battery. The only consideration is thatI performed my tests on a batterycapacity of 7 AH. This means that the20 milliohm shunt resistor will drop140 millivolts at the rated current.Since U1's current amplifier inputoverloads at 440 milivolts, this essen-tially means that the battery may sup-ply slightly over three times the ratedcurrent and the circuit will still meas-ure it accurately. This is importantespecially for motor drive circuits, as astalled or overloaded motor con-sumes several times its rated currentwhile the shaft is locked (as in startingunder load).

Input voltage range is from 5.6 to24 volts, which means that 5 to 10lead-acid cells may be used. The sixcell, nominal 12 volt battery isextremely popular due to its automo-tive origins, and is ideally suited forthis project. On the other hand, athree cell, 6 volt nominal battery,when discharged, would provide toolittle voltage to allow the 5 volt regu-lator to operate properly. In thisinstance, a switchmode regulatorwould be required.

A suitable SEPIC-switchmode regula-tor, which operates on battery volt-ages above and below its output volt-age, appeared in the April 1999 issueof Nuts & Volts.

If a different battery capacity is

required, the only consideration is tocalculate the shunt resistor such that itwill drop 140 millivolts at the ratedcurrent "C." Speaking of the shuntresistor, it is crucial, due to the lowohmic values involved, that a 4-wiredevice is employed. On a normal 2-wire resistor, the lead and junction

resistance, although minute, will stillintroduce significant errors.

Some current-sense resistors arespecifically designed for such a task, asshown in Photo 2. If you are unable toprocure one, you may still rig your own4-wire resistor as shown in Photo 3.

A normal, low value, 2-wire devicehas some pigtails attached as close aspossible to the resistor's body. Thus,wire and bonding pad resistanceerrors are avoided. Of course, alwayscalculate the resistor's power dissipa-tion: P = I * I * R.

I've specified several precision resis-tors in the circuit. The most importantare R4 and R9, which set the "dummy"voltage. If you may obtain 0.5% or0.1% tolerance resistors, then essen-tially the project's accuracy is set bythe shunt resistor accuracy. However,if you are cost conscious, a 1% toler-ance resistor may be used on thoselocations.

The only adjustment required is toensure that the reference voltage isset as closely to 2.600 volts as possi-ble. P1 is used for that purpose. Use a4-1/2 digit multimeter, if available, forcalibration.

It is essential that you do notchange the crystal frequency, as U1'sfrequency conversion is directly pro-portional to it.

40 SERVO 11.2003

Photo 3Homemade Shunt

Photo 2 Shunt Resistor

Figure 2

batteryfuelgage.qxd 10/8/2003 3:28 PM Page 40

Figure 2 shows the wiring connec-tions to interface the battery fuelgauge to your application. The speci-fied microcontroller has the necessaryflash-RAM, which will keep the cur-rent battery state if it is turned off.

When the project is powered up, itbriefly blinks all 10 LEDs to indicatethat the device is up and running.Don't substitute the Darlington tran-sistor for a garden variety NPN device,as it will not have the required gain.

As mentioned previously, this cir-cuit measures first-order chargeeffects exclusively, which essentiallymeans charge/discharge currents.Self-discharge and temperatureeffects are not considered in this sim-ple project, but could be incorporatedfairly easily.

Therefore, this constraint makes thisproject to be less accurate in applica-tions where the battery is seldom orinfrequently used. Your battery appli-cation should be used at least once amonth, to make self discharge errorsnegligible.

Resistors Unless noted, all 1/8 W, 5%

R1, R2, R3 1 KR4 1 K, 1%R5 10 WR6 2.2 KR7 390, 1%R8 20.5 K, 1%R9 7.32 K, 1%R10 22 KR11, R12 5 X 270 ohm networkP1 1 K, cermetRsh see text

Capacitors Unless noted, use the lowest voltageavailable for the rated capacitance

C1 - C4 0.033 mF, 20% X7R ceramicC8, C10, C14 100 mF elecrolyctic

Semiconductors

U1 AD7755 power meter IC, Analog DevicesU2 TL431 voltage reference, Texas InstrumentsU3 LM2925 regulator with reset, NationalU4 PIC16F84 microcontroller, MicrochipU5 10-LED bargraphQ1 MPSA28 Darlington NPNX1 3.5795 MHz crystal

Parts List

SERVO 11.2003 41

S

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Part 1

nightofthelivinghexapod.qxd 10/8/2003 4:31 PM Page 42

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WALKING ROBOTS:THEY ARE ONE OF THE MOST INTERESTING RESULTS OF TODAY'S ADVANCED TECHNOLOGY.

WITH THE POPULARITY OF MICROCHIP PIC MICROCONTROLLERS AND THE DEVELOPMENT OF COMPILERS

TO SUPPORT THEM, BUILDING MOBILE ROBOTS WITH “BRAINS ON BOARD” HAS NEVER BEEN EASIER.

44 SERVO 11.2003

In the past, a big problem withmobile robots was that they were

often tethered to their computers. Thesupport electronics, microprocessors,and batteries were too large to carryonboard. The robots, like the comput-ers that controlled them, were large,power hungry machines. Keeping therobots close to their host computersplaced limitations on the environmentsthat the robots could operate in andthe real world experiments that couldbe carried out.

The robots were restricted to universi-ty laboratories, out of the hands of theelectronics experimenters and enthusi-asts.

That has all changed ... Building the hexapod robot presented

in Figure 1 will allow you to experiencethe excitement of creating your ownartificial lifeform that can walk, explore,and react to its environment.

This hexapod robot is unique becauseit uses two DC gear motors containedin one unit to power the six legs. Onegear motor drives the three legs on the

left side of the robot’s body and theother gear motor drives the three legs on

the right side. The robots' body and legs are constructed

with standard aluminum pieces and fasten-ers that are available at most hardware stores. The robot controller circuit is designed

around the PIC 16F819, which contains 16 I/Opins and five 12-bit analog-to-digital converters.

Another feature of this device is a software selec-table internal oscillator that can be configured to

run between 2 and 8 MHz. With the sophisticationof the new PIC microcontrollers, the robot controller

board uses fewer parts than would have beenrequired a couple of years ago. The instructions for building and programming the

robot will be divided into two articles. The first article willdeal with the mechanical aspect of the construction and

the second part will deal with the electronics, program-ming, walking gaits and experiments.

Complete list of parts necessary to build the robot.

by Karl Williams

nightofthelivinghexapod.qxd 10/8/2003 4:48 PM Page 44

SERVO 11.2003 45

Step 1. Cut Out BaseThe first step in creating the robot is to con-

struct the aluminum base to which the legs,electronics, gearmotors, batteries, and thecontroller circuit board will be fastened.

This will require the use of a hacksaw(or a band saw with a metal cuttingblade), a power drill, table vise and ametal file. Cut and drill a piece of1/16-inch thick flat aluminum (4-1/2inches wide x 6 inches long) to thedimensions shown in Figure 2.

MECHANICAL CONSTRUCTIONTHE CHASSIS

Figure 3Body chassis drilling diagram.

Step 2. Drill Mounting HolesDrill all of the holes indicated in Figure 3

using a 5/32-inch drill bit except for the twoholes that are marked as being drilled witha 1/4-inch bit. Use a metal file to smooththe edges and remove any burs from thedrill holes. (Bend the aluminum inwardat 90-degree angles according to thebending lines shown in Figure 2.) Usea bench vise or the edge of a tableto bend the pieces.

Figure 2Body chassis cutting and bending diagram.

nightofthelivinghexapod.qxd 10/9/2003 7:06 AM Page 45

Step 4. Wire Them Up!Next, wire the battery packs together in

series to achieve a 6-volt output by followingthe wiring guide shown in Figure 4. (Notethat the 6-volt output wires are fed throughthe hole in the bottom of the chassis up tothe top side as indicated in Figure 4.)

If the lengths of the wires, measuredfrom the top of the robot chassis, arenot at least five inches long, add someextension wire.

Solder a two connector femaleheader to the end of the 6-volt out-put wires. Insulate each of the con-nections with a 1/2-inch piece ofheat shrink tubing.

Figure 5Underside view of the chassis.

Figure 6

Figure 4Battery wiring and power lead routing.

46 SERVO 11.2003

At this point in the construc-tion, the body chassis with thetwo 3-volt (2 x AA) batterypacks fastened to the under-side should look like the oneshown in Figure 6.

Step 3. Locate Battery Packs

Locate the two 3-volt battery packs (2 xAA) and fasten them to the bottom ofthe body chassis with two 2-56 by 1/4-inch machine screws and nuts. (UseFigures 4 and 5 as guides whenattaching the battery packs to thebody chassis.)

Thumbnail views

Fig. 4

Fig. 5

HEXAPOD-PPART

1

nightofthelivinghexapod.qxd 10/8/2003 4:49 PM Page 46

Step 5. Gear Up!Next, assemble the Tamiya twin motor gear-

box using the instructions (supplied with themotor kit) for a gear ratio of 203:1.

Apply the supplied lubrication to the gearsso that they mesh smoothly and run quietlywhen the motors are in operation. Use ahacksaw to cut each of the motor outputshafts to a length of 5/8 inch as indicatedin Figure 7.

Cut two pieces of 2-strand connectorwire to a length of eight inches each. Onone end of each of the cables, solder atwo connector female header and useheat shrink tubing to protect the solderjoints. Solder the first wire of the firstconnector cable to one of the powerterminals of the left motor.

Solder the second wire of the firstconnector cable to the remainingpower terminal of the left motor.Repeat this same procedure for thesecond connector cable and the right motor. Solder a 0.1 µFcapacitor (C4 and C5) across the terminals of each motor, shown in Figure 7, to reduce RF interference.

Figure 7Tamiya dual motor gearbox configuration.

Step 6. Get Some FeedbackLocate the two 4.5 K potentiometers and

attach a four inch long, 3-strand connec-tor wire to each one. Solder a 3-connec-tor female header to the other end ofeach wire as shown in Figure 8.

Figure 8Potentiometers with connector wires attached.

Step 7. Insulate and CalibrateInsulate each of the connections with a 1/2-

inch piece of heat shrink tubing. Before thelegs are attached to the chassis, each of thepotentiometer shafts must be set to theirmiddle positions. This is accomplished bythe procedure that follows.

Use Figure 9 as a guide to attach a 5-volt DC supply to the outer terminals ofthe first potentiometer. Attach theleads of a multimeter to the middle ter-minal and ground so that the voltagecan be read. Turn the potentiometershaft until you get a reading of 2.5volts. Calibrate the second poten-tiometer using the same proce-dure.

Figure 9Procedure to center the potentiometer shafts.

SERVO 11.2003 47

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Step 9. Give It Legs

Using the 1/2-inch by 1/8-inch aluminumstock, cut and drill six leg pieces labeled A,four outer leg linkage pieces labeled B,two middle leg linkage pieces labeled C,and two leg sensor linkage pieceslabeled D according to the dimensionsshown in Figure 11. Use a 5/32-inchbit to drill the holes.

CONSTRUCTING THE LEGSAND MOTOR SHAFT MOUNTS

Figure 11Cutting and drilling guide for the legand linkage pieces.

48 SERVO 11.2003

Step 8. Build Up the Chassis

Now that the gear-motors and potentiome-ters are wired, it’s time to attach them tothe body chassis. Position the gearmotor asshown in Figure 10, and secure it to thechassis using the two machine screwsand nuts that came with the motor kit.

Mount each of the potentiometers inthe 1/4-inch holes at the back of therobot chassis as shown in Figure 10.Make sure that the nuts are securedtightly so that the potentiometers donot move out of position when therobot is in operation.

Figure 10Twin motor gearbox and potentiometers attached to the chassis.

HEXAPOD-PPART

1

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Step 10. Shaft MountsFabricate the motor output shaft mounts

and potentiometer shaft mounts using 1/4-inch x 1/4-inch aluminum square stockaccording to the dimensions shown inFigure 12.

The motor shaft mounts are labeled asparts E and the potentiometer shaftmounts are labeled as parts F.

When the pieces are finished, threada 6-32 x 3/16-inch set screw in eachof the holes that were threaded withthe 6-32 tap.

Figure 13 shows a completedmotor shaft mount and poten-tiometer shaft mount.

Figure 12Motor shaft mount and potentiometer shaftmount fabrication diagram.

SERVO 11.2003 49

Now that the individual pieces for the legs and linkages have been constructed, it’s time to put them alltogether to form the mechanical part of the walking machine. Refer to Figures 14 and 15 when assemblingthe legs.

Step 11. Start by attachingone of the motor shaft mountpieces labeled E to the shaft of theright motor with the flat edge fac-ing away from the motor.

Make sure that the end of theshaft is flush with the face of themotor linkage and secure it inplace by tightening the set screw.

Step 12. Attach piece A to themotor mount with a 6-32 x 1-inchmachine screw with a nylon wash-er separating the two.

Step 13. On the samemachine screw, place anotherwasher, then linkage piece B, thena washer, and then another link-age piece B.

Secure all of the pieces togeth-er with a 6-32 locking nut.

Step 14. Attach two leg piecesA and linkage piece C to the chas-sis at the locations shown inFigures 14 and 15.

Step 15. Attach potentiometer

shaft mount F to the potentiome-ter shaft, but do not fasten the setscrew at this time.

Step 16. Attach linkage pieceD to piece F by placing a #6 nylonwasher between the pieces andsecure with a 6-32 x 1-inchmachine screw and locking nut.

Step 17. Starting from thefront of the robot, attach leg pieceA to linkage B with a 6-32 x 1-inchmachine screw and locking nut.

ASSEMBLINGTHE LEGS

nightofthelivinghexapod.qxd 10/8/2003 4:52 PM Page 49

50 SERVO 11.2003

Figure 16 Cutting, drilling, and bending guidefor the robot’s head section.

Separate the pieces with a 6-32 x5/16-inch plastic spacer.

Do the same with middle legpiece A and linkage piece C butadd two nylon washers along withthe 6-32 x 5/16-inch plastic spacer.

Step 18. Attach the back legpiece A to pieces D and B, with a6-32 x 5/16-inch plastic spacerbetween pieces A and D and anylon washer between pieces Dand B.

Tighten all of the locking nuts

with enough pressure to hold theparts in place, but still allow themto move freely without any resist-ance.

Step 19. Perform the aboveprocedure for the left side of therobot.

Step 20. When everything is inplace, use your finger to manuallyrotate the gearboxes so that themiddle leg on each side is in thedownward position and perpendi-cular to the chassis.

Step 21. Tighten the set screwon both of the potentiometer shaftmount pieces F. If you suspectthat the potentiometer shafts havebeen moved from their middlepositions, then re-calibrate eachone before tightening the setscrew (refer to Step 7).

When the mechanics are com-plete, add a rubber foot to the endof each leg. This will give the feetmore friction and help to gripwhen the robot is walking on slip-pery or uneven surfaces.

Step 22. Get Ahead

Fabricate the robot’s head using a 1 3/4 x 3 1/2-inch piece of flat 1/16-inch thick aluminum. Follow the cut-ting, drilling, and bending diagramshown in Figure 16.

Step 24. Recapitate

Attach the head to the body using two 6-32 x 1/2-inch machine screws andlocking nuts as shown in Figure 17.

Step 23. Sharp IR Detector

Locate the Sharp IR detector moduleand secure it to the head section withthe mounting machine screws andnuts that came with it. See Figure 17for orientation.

HEAD AND INFRAREDSENSOR MOUNT

Figure 17Finished mechanical assembly of the robot.

HEXAPOD-PPART

1

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The mechanics and sensors ofthe walking robot are now assem-bled into place.

All that is needed to bring therobot to life are the electronics andsome microcontroller programming.

In the next part of the Hexatronseries, the electronics, wiring, sensors(infrared and leg position) and pro-gramming of the PIC 16F819 micro-controller will be covered.

Visit the author's website formore information about the project(www.thinkbotics.com).

AUTHOR’S BIO

Karl P.Williams is the author oftwo robotics books titlesInsectronics: Build Your Own SixLegged Walking Robot (ISBN

0-07-141241-7) and Amphibionics: Build Your Own Biologically Inspired Robots (ISBN0-07-141245-x), both published byMcGraw-Hill.

He hosts a robotics website at(http://home.golden.net/~kpwillia)and can be contacted throughwww.thinkbotics.com

Figure 15 Leg and linkage partsassembly diagram — inside view.

Figure 13 Completed motor andpotentiometer shaft mounts.

Figure 14 Leg and linkage partsassembly diagram — outside view.

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Circle #122 on the Reader Service Card. SERVO 11.2003 51

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nightofthelivinghexapod.qxd 10/9/2003 7:11 AM Page 51

Build A One-PoundFighting Robot

PPPPAAAARRRRTTTT 2222

by Patrick Campbell

Put the Finishing Touches on Your Mini Robot!

PPPP art 1 of my article ran in theAmateur Robotics Supplement#2, back in August of 2002,

where I explained how to design aSOZBOT — from laying out the drive-train to architecting an effectiveweapon. This part finishes off the proj-ect and brings all the subsystemstogether to form a fierce 16 ounce

fighting machine, which I namedDemonic.

Figure 1 shows an exploded viewof the design and attached is a roughparts list. With all the purchased partsin hand, I only need to make a fewparts — the chassis top and bottomout of carbon fiber sheet, the weaponblade and two mounting plates forthe weapon out of aluminum, and

some short shafts. First, we'll startout with the carbon fiber

parts.

PartsFabricationCarbon FiberChassis Panels

When workingwith carbon fiber,

you must keepsafety in

mind. Carbon fiber is made by takingstrands of fiber and weaving it into afabric. Typically, the fabric is epoxyimpregnated and cured under heatand pressure in an autoclave. Thefibers are very strong, lightweight,and small in diameter. Although it isnot considered a hazardous material,you should wear safety goggles, dustmask and gloves to avoid coming intocontact with the fibers when you areworking with it. The dust generatedfrom cutting, sanding and drilling is

what you don't want to get incontact with.

In my case, Imounted the 0.030-inch thick carbon fiberpanel in my CNC millingmachine and cut outthe shape I designed inmy CAD program. Irealize most people

FIGURE 1

PARTS LISTITEM QTY PART NUMBER DESCRIPTION1 2 SOZBOTS P/N BM3MM Dual Bearing Mount2 2 SOZBOTS P/N MMGH01 Motor Mount3 1 SOZBOTS P/N SOZDSC-M SOZBOT Speed Controller4 1 Custom Fabrication Bottom Chassis5 1 SOZBOTS P/N RCRXFM5 Radio Receiver6 1 Custom Fabrication Top Chassis7 1 SOZBOTS Weapon Motor8 1 10 Tooth Gear Weapon Drive Pinion9 2 7.2V 1000 mAhr LiPoly Battery

10 1 50 Tooth Gear Weapon Disc Gear11 1 Custom Fabrication Weapon Left Mount12 2 SOZBOTS P/N BE3MMF Flanged 3mm Bearing13 1 Custom Fabrication Weapon Disc14 1 Custom Fabrication Weapon Right Mount15 1 SWITCH Switch16 1 Custom Fabrication Switch Block17 4 SOZBOTS P/N W50T30D 50mm Wheels18 2 SOZBOTS P/N GH27MOT Gearmotor19 4 SOZBOTS P/N CHS16HEX Chain Sprocket

52 SERVO 11.2003

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don't have access to a CNC machine,but carbon can be cut like most othermaterials. It can be cut with a hacksaw, Dremel, router, shear, snips andeven by scoring with a sharp knife ifit's thin enough. It’s tough stuff andtends to wear down your tools, so usesharp carbide or diamond tippedblades if possible. I then drilled clear-ance holes for all the screws. After cut-ting and drilling, I used a file and sand-paper to smooth off the cut edges.This ensures that the finished part issafe to handle without gloves and theedges end up nice and smooth. BeforeI removed my gloves and dust mask, Iwashed the parts in cold water.

If you don't want to work withcarbon fiber, you can choose a varietyof materials from foamed PVC sheetto sheet metal. The appeal of carbonfiber is its high stiffness, high strength,and light weight, but there are othermaterials that can do the same job atincreased weight.

Aluminum Blade and Mounts

These parts were all cut from 1/4-inch aluminum on my CNC millingmachine. Although the blade is a fair-ly difficult part to fabricate withoutsuch machinery, you can go down toyour local hardware store and find asmall cutting blade of the same diam-eter and adapt it accordingly. Themounts are a bit tougher to fabricate,but your challenge will be to buildparts with the same functionality withthe tools you have on hand.

The weapon blade uses 3mmbearings which are pressed into theuprights. You can use a low frictionplastic, like Delrin (acetal), and youwon't need to worry about bearings.Delrin is a good material choice for theuprights as it is easy to work with andvery durable. The weapon shaft is 1/8-inch diameter with the ends turneddown to 3mm (0.118-inch) to fit intothe bearings. The step on each end ofthe shaft captures the shaft in thebearings. I used flanged bearings tocapture them between the uprights.The shaft is pressed into the weaponblade and I still used some shaft spac-

ers to keep the bladecentered between theuprights.

The mounts aretapped #4-40 on the bot-tom. It is attached to thecarbon fiber with smallbutton head screws. Oneof the holes is on centerwith the motor, so byusing a long enoughscrew, it bottoms out onthe motor, retaining it inthe upright.

Wheel Axles

The wheel axels need to be cut tothe correct length. This is done with ahacksaw, and then filed to take off thesharp edges.

Robot AssemblyAll the parts are ready to go —

now it’s time to assemble!

Rear Motor and Wheel Assemblies

First, we insert the flanged bear-ing into the mount with the flange onthe inside of the block. Then we takethe shaft adapter with the shaftpressed in it and insert it into the bear-ing. Then we mount and install themotor with the two screws and lockdown the setscrew on the shaftadapter to the motor output shaft.Press on the 16-tooth chain sprocketto the shaft, and then press on thewheel and the assem-bly is complete.

Front WheelAssemblies

Insert the twobearings into themount with theflanges on the insideof the block, and theninsert the shaft intothe two bearings withthe supplied spacerbetween the bearings.The setscrew on the

spacer will hold the shaft in place, soadjust it to determine how much shaftoverhang you need. Now press thechain sprocket and the wheel on theshaft. If you don't want the wheel topop off in battle, you might want touse a drop of superglue.

Mounting Drive Train to Chassis

Take all four assemblies and screwthem to the bottom chassis usingsome #4-40 x 3/16 button headscrews. Align the sprockets and runthe chain over them. The chain is easyto work with — just use your finger-nails to take links apart and put themback together again. Figure 2 showsthe drive train mounted to the bottomchassis.

Weapon Assembly

Attach the gear to the saw bladeand insert the shaft through the bore.It’s important to keep the gear cen-

FIGURE 2

FIGURE 3

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tered as much as possible to the cen-ter bore of the blade to ensure thatthe gears mesh correctly. Install thebearings in each mount and thenmount the motor to the left motormount. Attach the left motor mountto the chassis, then the blade axle,and then screw in the right side to thechassis. I used fiber washers as shaftspacers to keep the blade centered onthe shaft, but almost any spacer willwork. Figure 3 shows the weaponassembly attached to the chassis.

Electronics

Except for the chassis top, therobot is mechanically ready. Now we'llstart with the electronics.

Radio Receiver

The receiver is secured to the bot-tom chassis using double-sided tape.You can save weight by removing the

receiver enclosure, butsecuring the internalelectronics is a littletougher. You can stilluse double-sided tape,but you also have toworry about protect-ing the electronics.

The antenna issimply a short wirecoming out of thereceiver. Do notchange the length ofthe wire and don'tloop the wire on itself.Antennas are best if

kept in a straight line, but for robots,the best way is to zig-zag it. Figure 4shows the antenna taped to the bot-tom of the robot. Since we are typical-ly operating the robot from no morethan seven feet away, range is usuallynot an issue, but getting a good signalto the robot is critical.

The lightweight receivers used inthese robots tend to be glitchy com-pared to the heavier and usually moreexpensive ones. The key difference isthe lighter ones are single conversionand tend to be more susceptible tointerference compared to dual conver-sion receivers.

Because of this, it's important tohave good wiring and a properlymounted antenna to reduce glitchingin the robot.

Speed Controller

The speed controller is the heartof the robot — it connects to the

power source, tothe radio receiver,and to all themotors. Because ofthis, there is a gooddeal of wiringinvolved with thisunit. It’s best todetermine themounting locationsof your electronicsand then figure outthe shortest wirelength that willwork. Short wires

help minimize your weight, reduceclutter, and avoid electrical noise.Twisting your power leads will alsohelp to keep your wires neat andreduce interference. I prefer to useTeflon wire because of its high temper-ature characteristics. Twisting the wireis very easy — take two equal lengthsof wire, clamp one end in a vise andthe other in your cordless drill chuck.Run the drill while keeping tension onthe wire until you get the amount oftwist you are looking for.

The radio receiver connections arevia three wire leads that get solderedinto the speed controller. The otherend of the lead is a connector thatplugs into the receiver. Next, the bat-tery lead gets soldered into the boardand the hot lead is cut and wired tothe power switch. The power switchshould always be located away fromthe weapon, and in a location thatmakes it difficult for the switch to gethit accidentally, especially by anotherrobot. Figure 5 shows the wiring.

Battery

I was planning on using NiCd bat-teries, but switched to lithium polymer(LiPoly) to save weight and gain runtime. For less weight, I can have aboutfour times the battery capacity. Thisallows me to have just one battery inthe robot that I top off betweenmatches. I never fully drain the batteryin a bout and can easily run twomatches back-to-back, which can hap-pen quite often in double eliminationcompetitions.

LiPoly batteries have improved tothe point that they can be used athigh discharge rates — up to 8C. Thismeans that my 1,000 mAH batterycan continuously source 8 amps. Thisis just enough current to feed my driveand weapon motors. I used double-sided tape to secure the battery and Ican charge it while it's in the robot. Ifyou are using a battery that you needto remove to charge, then consider amounting method that is easily serv-iceable.

There is no way to fast charge aLiPoly, but having the extra capacity

FIGURE 4

FIGURE 5

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means that if you keep the robot oncharge between matches, one batteryshould last you for the day. But, alwayshave backups as parts can easily getdamaged in a match.

Motors

To help eliminate motor noise, it'sbest to solder three 0.01 µF capacitorson the motors — from each brush ofthe motor to the motor body andbetween each brush. This is veryimportant on cheap toy motors, butnot always necessary on good qualitymotors. Remember to keep the motorleads as short as possible.

Final Assembly andTesting

Whenever you first power up therobot, keep safety in mind. I discon-nect the weapon motor so that I cancheck the drive system and radio sys-tem first. Block the robot so its wheelsdon't touch the ground. Turn the radiotransmitter on first and then therobot.

Once you confirm the radio andthe drive are working, turn the robotoff and connect the motor. Power-upagain and test. If everything works,get plenty of driving practice for thenext competition.

ConclusionSOZBOTS are an excellent way to

get into the sport of fighting robots.Half the fun of competing is designingand building your own robot, usingyour own designs.

The other half is the actual com-peting. It's a great way to challengeyourself to come up with a solutionthat is better than the other guy’s aswell as challenge your ability to build adurable robot that can handle the rig-ors of battle. And because the robotscan only weigh up to one pound, thecost of building a robot and compet-ing is far less than any other weightclass.

Demonic has entered four compe-titions since being built, and has won7 matches out of 15. Not quite 50%,but future improvements will give it abetter chance.

A couple of improvements includereplacing the aluminum blade withtitanium and adding a wedge in thefront to keep other robots from get-ting underneath and pushing him

around. Good luck with your one-pounder and see you at the nextSOZBOTS event!

SSixtixteeneen OZOZ roroBOBOTTSS!!To learn more about these SOZBOTS

and their fighting events, visitwwwwww.sozbots.com.sozbots.com.

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SOZBOTS.qxd 10/8/2003 10:46 PM Page 55

This sensor mimics the activity of our

own human eyes, which move in

rapid, discrete steps to take in their

surroundings.

Tracker.qxd 10/8/2003 12:58 AM Page 56

As I write, a prototype of "TheTracker" watches my every movewith attention as keen as that of

a dog expecting a treat — and everytime I leave my seat, it turns its head to follow my movements around the room.

The Tracker is a robotic head whichemploys two electronic "eyes," each ofwhich is extremely sensitive to movingshadows. By adding some simple logicto the eyes, and a "power section" witha robust DC motor, The Tracker willturn a head to track the motion of aperson walking by.

Sophisticated circuitry is normallyused to track motion in this way. TheTracker, however, uses cheap and com-mon components throughout, in whatis a relatively simple circuit. If its lefteye detects motion, its head rotatesleft. If its right eye detects motion, its head rotates right. If both eyesdetect motion simultaneously, it simply"stays put."

The Eyes

The success of The Tracker as adesign comes down, in the final analy-sis, to its eyes. These need to meet twoimportant criteria.

First, they need to be very respon-sive if they are to pick up moving shad-ows at any distance. Second, they needto auto-adjust to ambient light, so as torespond to a fairly wide range of light-ing conditions as they scan a scene.

On the second count, The Trackeruses what is called a "passive" detec-tion system. This means that it doesnot use a fixed light source which isintegral to the design, but responds torelative fluctuations in light level.

I chose "shadow sensors" for theeyes (sometimes called "light sen-tinels"), since in certain situationsthese have important advantages overinfrared or ultrasound.

First, both infrared and ultrasoundare unable to sense motion throughglass. Second, infrared is unable tosense objects which are thermallyindistinguishable from their back-ground. The Tracker, through its use of

shadow sensors, will track shoppersthrough a store-front window or detect"thermally neutral" motion, such asluggage moving on a conveyer belt.These features are described in greaterdetail below.

Block Diagram

The block diagram in Figure 1gives a simplified representation ofhow one of The Tracker's eyes works.Note that several components areomitted from this diagram.

A light dependent resistor (LDR)forms the lower arm of a potentialdivider, and this presents a potential atpoint X of approximately half the sup-ply voltage. This potential fluctuateswith changing light levels (i.e., shad-ows in clothing).

The potential at point X is thenpresented simultaneously to the inputsof two bilateral switches. An astableoscillator with an integral divider alter-nately switches the bilateral switchesat several Hertz, so that the two capac-itors at the inputs are alternatelycharged.

Since the resistance of the bilateralswitches in the off state is very high andthe input impedance of the op-ampcomparator is very high, the charge onthe capacitors is "trapped" in thespaces between the bilateral switchesand the comparator. These are referredto as sample-and-hold circuits.

As the light level rises and falls, the

charge (that is, the potential) at thecomparator's inverting input exceedsthat at the non-inverting input and thecomparator's output goes low, thustriggering a monostable timer. Theeffect is that the eye compares lightlevel over time.

One of the toughest problems tocrack with the present circuit was thatof the eye's response under AC light-ing. This is because the circuit needs todistinguish between quick and subtleshifts in light level on the one hand,and the flicker of AC lighting on theother. This problem was effectivelysolved for incandescent lighting,although harsher lighting (i.e., sodiumlamps) could negatively affect sensitiv-ity.

The core of the solution lies in acarefully chosen capacitor (Figure 1)wired in parallel with the LDR, whichsmoothes out ripples at point X. Whilethis reduces the overall sensitivity ofthe eye by about one-third, it alsoreduces AC ripple by about 90%. Inconjunction with other select compo-nent values in the "eyes section," thisbrings about a very significant improve-ment in response.

The "sure bet" range of The Trackerunder AC incandescent lighting shouldbe more than eight feet — and abouttwice this under natural lighting.However, with careful adjustment andtweaking, as described below, it shouldbe possible to extend this to the fullpotential range of the eyes. These are

tHE TRACKER by Thomas Scarborough

.:. Figure 1 .:.

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Tracker.qxd 10/8/2003 1:00 AM Page 57

capable of spotting a person walkingunder natural lighting at 60 feet, orunder AC incandescent lighting at 20feet, without lenses.

Motor “Blanking”

The block diagram in Figure 2gives a more simplified overview ofThe Tracker's logic, or brain.

The Tracker's brain is small, per-forming only an AND operation and anOR operation on the two monostabletimer's outputs, with the help of fourbilateral switches.

If either eye triggers individually(which is OR), the other eye is instant-ly disabled. In fact, both eyes are dis-abled to prevent any interference fromthe power section and motor, whichdraw a heavy current and send ripplesthroughout the circuit. The eyes aredisabled as long as the motor is ener-gized, and continue to be disabled foras long as a timing capacitor deter-mines (C12 in the full circuit diagram).This "blanks" the action of the motor,and gives the circuit sufficient time tocompose itself after each movement ofThe Tracker's neck.

This blanking has more than onepurpose. First, if there was no blanking,the eyes would see motion all the timeas The Tracker turned its neck. The cir-cuit blanks out the motion of a spin-ning world around it, as well as anyphysical vibrations that might becaused by the turning of its neck.

Second, if both monostable timerstrigger simultaneously (which is AND),both timers are instantly reset. Thisremoves any conflict between the twoeyes (and thus any conflict at themotor), and causes The Tracker to wait for the next trigger pulse fromeither eye.

Circuit Detail

Much of this circuit (see Figure 3)represents standard electronics, andrequires little explanation. At the sametime, there are a few critical featureswhich I shall highlight here.

Most importantly, the circuit needsto combine the extreme sensitivity ofthe eyes with the heavy switching ofthe power section and motor.Therefore it uses supply decouplingcapacitors throughout. (In the interestof simplicity, these are not reflected inthe full circuit diagram).

The circuit also uses small valuecapacitors — in particular C1 and C12 —and high value resistors — in particularR1, R6, and R13. C12 dispenses with agood practice parallel resistor for thesake of further discouraging ripples onthe supply. Also note capacitors C8-C11, which help to stabilize the twoeyes. These in particular need time tosettle at switch-on.

The 4047B CMOS oscillator (U1)provides — through an internal divider— a near perfect mark-space ratio at itsoutput pins 10 and 11, to switch bilat-

eral switches U2a to U2d alternately. U4 and U5 were chosen particular-

ly for their high input impedances,which are necessary so that C4 to C7will retain their charge. Also, they werechosen specifically for their provision ofan offset-null adjustment, which isused to balance the differential inputstage so that the inverting input is nor-mally higher than the non-invertinginput. Failing this, the potentials at the two inputs would be too close forcomfort, and might or might not triggerthe ICs.

While LDRs have slower responsetimes than other light sensitive devices,two LDRs were chosen for this circuitbecause they are common devices,and may easily be interchanged withsimilar devices of the same family. Thisis not always the case with photo-tran-sistors or photo-diodes, which havesome awkward relatives. Note that ifphoto-diodes are used, the cathodeswould normally be wired to points Aand C in the circuit. An LDR is com-pletely non-polar.

The first stages of the circuit espe-cially require quietness to functionproperly. Therefore, no LED is used todisplay the switching action of U1,although this might be helpful. Also, noLED is used to show the state of theoutput of either U4 or U5. Where anLED is indeed essential in the firststages (LED1), this uses a high valueballast resistor (R6). Therefore, anultrabright or high efficiency LED isused in this position.

A special problem presents itself inthe form of the power section (U7 andits surrounding components) andmotor M1. This has already beendescribed in brief.

Taking the example of U7a, whenthe output of U7a goes high, capacitorC12 is charged, and bilateral switchU6c conducts. This means that thepotential at the junction of R11 andU6c goes high. Therefore, with triggerpin 6 being held high, this is disabledfor a moment, giving the circuit time to settle after the motor has been energized.

LED2 and LED3 are included in theblanking described. As small as theirpower consumption is, these alonewould be capable of significantly desta-

.:. Figure 2 .:.

the tracker

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bilizing the circuit during switching.Finally, a power MOSFET H-bridge

is used to turn the motor either clock-wise or counterclockwise in responseto pulses from IC7 ouput pins 5 and 9.The specified MOSFETs will turn anysmall motor without the need for heatsinks, yet remain generously withintheir limits. D4 and C15 are included tosuppress back-EMF.

Current consumption of TheTracker is less than 10 mA on standby,so that operation off a 12 volt 7 Ah bat-tery is feasible, and would likely carrythe circuit through a few days of con-tinuous use in a store-front windowbefore requiring a recharge.

Finally, it would be a fairly simplematter to add speech to The Tracker. Asan example, an ISD1400-series single-chip record and playback device wouldprovide a simple option if suitable trig-ger inputs were arranged. Since thesedevices have versatile addressing capa-bility, various spoken messages couldbe incorporated in the circuit.Comprehensive data is available atwww.isd.com

Electronic Construction

The Tracker is built on two PCBs,one each for the processing and sens-ing circuitry. Two further PCBs (anupper and a lower plate, consisting ofthree concentric circles of copper track)

are required for the construction of theneck, which in the prototype has free360° rotation. PCB patterns are avail-able for download on the SERVO website (www.servomagazine.com).An early prototype used an umbilicalcord between PCB 1 (the body) andPCB 2 (the head), which on one occa-sion led to complete self-strangulation!The upper plate makes contact withthe lower plate through three sprung wires (or brushes) as shown in thephotographs.

Note that U1, U2, U6, and U7 areCMOS devices, and require care whenhandling (first discharge your body toground). Because PCB 1 is not small, Iwould recommend the use of dual-in-line pin (DIP) sockets throughout.

Starting with PCB 1, begin by sol-dering the solder pins, the seven DIPsockets, and 32 jumper wires. Thensolder the resistors, the diodes, thepotentiometers, the capacitors, and thepower MOSFETs, finishing with theLEDs (these should have suitably longlegs for mounting on the case — andnote orientation). Use suitable lengthsof connecting wire to connect S1 andthe DC power socket (points F and G inFigure 3). The three solder pins nearpotentiometer VR1 are taken to thelower plate of the neck as shown, withsuitable lengths of connecting wire.

Turning to PCB 2 (the smallerPCB), solder the resistors and capaci-

tors, then add the LDRs — leaving longenough legs for these to be "splayed"(see below).

When an LDR is in its "naked"state, it has a very wide viewing angle,and its sensitivity is dull. The sensitivitymay be greatly increased by making it"look" down the length of a narrow,black tube. In this case, three-inch longblack tubes are recommended. Formaximum range, try longer tubes —however, this reduces the field ofvision, which can be self-defeating insome lighting situations. The tubes are later fixed to the head assembly, so that vibration is reduced to a minimum.

Once soldering is complete, insertthe ICs in the DIP sockets, observingthe correct orientation, and mountpotentiometers VR1-VR3, LED1-LED3,and S1 and the DC power socket onthe case.

Mechanical Construction

The motor is mounted firmly onthe top of the case, with its "face"being flat horizontal. This is a 12 voltDC bidirectional motor with fairly lowrevs (650 RPM in the prototype), andgood torque. The circuit allows formore than a little latitude when itcomes to the motor's speed, so thatvarious, similar DC motors may betried.

the tracker

.:. Figure 3 .:.

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Wire up the bottom neck plate,mounting it on the face of the motor.Solder sprung wires (brushes) to theupper neck plate, and fix this on themotor's shaft, ensuring that all thebrushes make good contact with thecircular copper tracks on the bottomplate, and that the upper plate is flatparallel with the bottom plate. Wipeboth plates with alcohol or methylatedsolvent before securing them, sinceresidues from their manufacture mightdirty the brushes.

Construct a central cylinder whichwill enable the upper plate to fit tightlyonto the motor's shaft. I did this withsoft copper plate which I wrappedtightly round the shaft, then solderedrigidly into place. The upper plateshould then slide tightly on and off themotor's shaft. If this proves not to besturdy enough, epoxy glue is suggest-ed. A head is then built onto the upperplate. For this I used stiff card stock,and added some sparse "decoration"as seen in the photographs. The headconstruction also serves to support theeye-tubes.

The eye-tubes were splayed at 65°in the prototype. If this angle isreduced, The Tracker may lose you tooeasily as you walk past.

Set-up andTroubleshooting

Turn back (counterclockwise) all

three potentiometers, plug 12 voltsDC into The Tracker's DC powersocket (center pin positive), thenswitch on. If a 115 volt AC to 12 voltDC wall pack is used, this should berated 1 amp with 30 mV RMS rippleor less, otherwise the circuit's sensi-tivity could be compromised. Inother words, a high quality regulatedwall pack is required.

At this point, The Tracker's headshould not be moving, except per-haps for one or two twitches atswitch-on. The circuit takes a minuteor more to fully settle, and mayexhibit unexpected behavior beforethis.

Turn up (clockwise) dual poten-tiometer VR1 until LED1 illuminates.If this does not illuminate, the lightlevel might be out of range. Unless itis far out of range, this should notpresent a problem — simply turn thepotentiometer to the brightest(clockwise) or dimmest (counter-clockwise) light setting. LED1 mightblink on and off during operation,depending on the light level per-ceived by the circuit at each turn ofthe neck.

Next, turn up (clockwise) dualpotentiometer VR2 until LED2 andLED3 blink when there is motionbefore the eyes. If you turn this uptoo far, the AND logic describedabove will kick in and tend to cancelout the response of both eyes — or

one or the other LED will blink ran-domly. If the head is properly con-nected, it will now twitch both clock-wise and counterclockwise when itsenses motion before the eyes.

We now require more decisivemotion of the neck. For this purpose,dual potentiometer VR3 is turned up(clockwise) until the neck turnsthrough a suitable arc to effectivelytrack a person walking by. The set-ting of VR3 will vary according to themotor used, and the distance andspeed of people walking by. Themotor should turn the neck so thatthe eye which is triggered advancesits position ahead of the motion ithas detected (i.e., ahead of a per-son's path), while not advancing theother eye too far. Each time the neckturns, the head should more or lessturn to face you directly. If the head

.:. Main processing PCB .:.

Resistors All 1/4W, 5% unless notedR1 470 KR2, R5 33 KR3, R4 39 KR6 22 KR7, R8, R13 220 KR9, R10, R14-R17 1 KR11, R12 47 KLDR1, LDR2 NORP-12VR1, VR3 Dual gang 100 K linear potVR2 Dual gang 47 K linear pot

CapacitorsC1, C15 100 nF C2, C3 1 µF electrolytic 16 VC4-C11 47 nF C12 680 pF C13, C14 470 nF C16-C21 100 µF electrolytic 16 VC22 1000 µF electrolytic 16 V

SemiconductorsD1-D31N4148 D4 1N4001D5 1N5400 (or to suit motor)LED1-LED3 5 mm ultrabright red LEDTR1-TR4 IRF510 power MOSFETU1 4047B CMOS oscillatorU2 TL072CN dual JFET op-ampU3, U6 4016 CMOS quad bilateral switchU4, U5 TL071 JFET op-ampU7 ICM7556IPD dual CMOS timer

MiscellaneousM1 12 volt DC gearhead motor

(All Electronics CAT # DCM-208)S1 On-off switch rated 1APS1 (optional) 12 volts DC 1 amp power supply

<30 mV rippleSK1 DC power socket to suit PS1

60 SERVO 11.2003

the tracker.:. Parts List .:.

Tracker.qxd 10/8/2003 1:01 AM Page 60

turns the wrong way, simply reversethe leads of the motor.

If the circuit does not work asdescribed, switch off and carefullyre-check. Ensure that there are nosolder bridges on the PCB, that allcomponents are inserted correctly,and that all inter-wiring is correct.

Simple trouble-shooting of thecircuit may be done with an LED anda 1K series resistor, with the LED'scathode being wired to ground.Touch the resistor to pin 10, then topin 11 of U1. The LED should flashboth times. Touch it to U4 pin 6,then to U5 pin 6. With the correctsetting of VR2, the LED should blinkboth times when a hand is moved infront of the corresponding eye. Allbeing well at this stage, any furtherproblems will lie in U6, U7, or thepower MOSFETs. U2 is incidental tothe circuit, and is unlikely to causeany problems. A further problem

might lie in interference betweenthe two eyes. If a hand is moved infront of one eye and the LED of theopposite eye flashes also, then thereis interference.

Assuming that the circuit hasbeen given ample time to settle, tryturning back VR2. If this leads topoor sensitivity, a poor quality powersupply would be the No.1 suspect.The perfect solution in this casewould be a 12V battery. Interferencefrom the motor or physical vibrationof the head should be the next sus-pects. The solution in this casewould lie in a longer blanking peri-od, by increasing the value of C12. Imyself needed to add 470 pF in par-allel with C12 after I added a head tothe "head scaffold," due to increasedvibration and momentum with theadded weight. Make sure that allparts of the head are well secured.Another potential problem would beparticularly bad lighting conditions(i.e., sodium lamps). In this case,"easier" lighting would be recom-mended, although an increase to thevalues of C2 and C3 might help. TheTracker will work best in situations ofgood contrast (i.e., shadows on awhite wall). If a room has large, darkareas on the one hand, or especiallybright areas on the other (such aswall lamps) The Tracker mightbecome confused — due partly tothe fact that it sees "in mono-

chrome" and dark or light patchesmight obscure shadows. Uniformbrightness in a room will work best.If The Tracker is to be used in brightdaylight or sunlight, the values ofVR1 and R7-R10 should be adjustedto give a potential of about half thesupply voltage at point X.

With some experimentation, TheTracker may be set to transitionseamlessly from natural to AC light-ing — but this, unfortunately, will notoccur at maximum sensitivity forboth. If maximum sensitivity undernatural lighting triggers the circuitunder AC, then adjust for maximumsensitivity under AC — and vice versa.

The author may be contacted [email protected]

.:. Head scaffold with neckplates and sprung wires .:.

the tracker

SERVO 11.2003 61

.:. Sensor PCB .:.

S

Tracker.qxd 10/8/2003 1:01 AM Page 61

Smart Dust Millirobots Take aWalk

While mostrobotic engi-neers are work-ing on makingbigger robots,UC Berkeley pro-

fessor Kristofer Pister has been follow-ing the idea that smaller is better.Using circuit designing techniques, he'sbuilding robots that will soon be invisi-ble to the naked eye. They use micro-electromechanical systems (MEMS),which act like an inchworm to give thebots better crawling capabilities. Whilethese robots aren't quite capable ofoutrunning Carl Lewis, they have

proven their abilities to scamper about.Talk about wanting to be a fly on thewall — Pister's microbots may finally beable to let you know what your co-workers really think about you.http://robotics-society.org/servo/001

Robot Tries to Put Sniffer DogsOut of Work

Pity the poor sniffer dog. Firstsomeone shoves a dirty shirt under hisnose, and then he drags some guythrough the woods looking for the badguys. Andy Russell of MonashUniversity in Australia hopes to put thesniffer dogs out of work. He's devel-oped robots that can detect a scentand follow it to its source. Althoughnot yet as "scents-itive" as dogs, thebots will eventually be able to precisely recognize individual odorsand alert humans to their source andexact composition — not just "it's a bomb," but such details as the exact type of explosive used. The botsshould have no problem finding mylaundry pile ... http://robotics-society.org/servo/002

Robots Try to Put David BeckhamOut of Work

Pity poor PoshSpice — currentlymarried to one ofthe greatest soccerplayers ever. FIRA —the Federation ofI n t e r n a t i o n a lR o b o t S o c c e rAssociation — held its annual competi-tion in Vienna at the beginning ofOctober. Robots, both walking and onwheels, are quickly catching up to usmere mortals. The goal of FIRA is tohave a bipedal robot team beat ahuman team by 2050. T

he recent games consisted of bothwheeled and bipedal bots — the goal ofthe wheeled bots being to accuratelyfind the ball, opponents, and goal —while the bipeds focus on being able tostand and kick. Soon, the two typeswill converge to create autonomousbipedal robots that can independentlyfind the ball, determine friend fromfoe, kick the ball into the opposinggoal, and just about anything elseMessr Beckham can do. Victoria willneed to invest in batteries ...http://robotics-society.org/servo/003

Snake Robots Slither Into theFuture

Tokyo research-es have developednew snake robots tohelp find survivorstrapped in collapsedbuildings after earth-quakes, explosions,and bombings.Fumitoshi Matsuno of Tokyo’sUniversity of Electro-Communications'Mechanical Engineering and IntelligentSystems, has spearheaded the projectwhich developed snake-bots that "cango into narrow places and their longand thin bodies can disperse theweight to prevent a secondary collapseof wrecked structures," something thattraditional wheeled bots can't do.These robots will really advance the science, but they could have saved

62 SERVO 11.2003

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Welcome to Robytes, SERVO'scollection of random bits ofrobot news from around the

world. Every issue you'll get a goodcross section of what's going on. Gota good story on robots? Email me:[email protected]

And, if you'd like to get even morerobot news delivered to your in-box(no spam, just robo-news), drop a line:[email protected]

— David Calkins

Robyte.qxd 10/9/2003 2:38 PM Page 62

themselves a lot of time if they'd calledGavin Miller first.http://robotics-society.org/servo/004

Korean Industry Works to DevelopService Robots

Home robots have long escaped ourdreams of an in-house service bot thatwill do our laundry, dishes, and take thedog for a walk. But the InternationalFederation of Robotics is hoping that in-home service robots will soon be asprevalent as cars — growing from a $400million dollar industry in 2003 to a $2.2billion dollar industry by 2005 — and asmuch as $70 billion by 2010. TheKoreans, hoping to capitalize on theexplosive growth, are focusing their ener-gy on creating everything from vacuumbots to cleaning bots. With heavy hitterssuch as Samsung and Hyundai leadingthe way, better bots are within our gen-eration. I just hope that my future butlerbot has as cool a voice as B-9 did in "Lost in Space." http://robotics-society.org/servo/005

New Walking Robots for Under$100.00

Mark Tilden,the famous inventorof BEAM roboticsand annoyer of gen-erals everywhere, iscoming out withwalking robotswhich will giveASIMO a "run" for its money. Spurnedby the success of BIO bugs, and on loanfrom NASA (until they stop crashing hisrobots into mars), he's introducing anew robot — the "RoboSapien" — a fullfunction, fast moving robot minion suit-able for all your world dominationneeds. It features real multi-speed fastdynamic walking, running, and turning,67 pre-programmed functions includingpick-up, throw, kick, sweep, dance, fart,belch, rap, and half-a-dozen differentkung-fu moves. And it even speaks flu-ent international "caveman." All thiswithout a computer. The big question,of course, is will it take my Aibo for awalk, or try to steal its lunch money. http://robotics-society.org/servo/006

Nanorobots to Swim Through theBloodstream

As a boy, Ir e m e m b e rwatching theold movie" F a n t a s t i cVoyage" (later

remade as "Innerspace") about aminiaturized submarine that cruisesthrough a man’s body in order to per-form microscopic surgery, and think-ing "No way could they do that! Coolmovie though." I've learned a lot inmy old age. One thing is never to say"No way they could do that."

Well, Rutgers University is build-ing robots that someday will travelyour bloodstream to repair damagedcells, tissues, and DNA.

A prototype of their Nano Motoris expected to be unveiled in 2007,with research and developmentfunded by a four-year$1,050,017.00 grant from theNational Science Foundation and itsNanoscale Science and Engineeringprogram.

These motors — 1/50,000th thewidth of a human hair — will trulyrevolutionize how we look at medi-cine and the body. So long as youdon't sneeze them out ...http://robotics-society.org/servo/007

To the Moon, Alice!

The EuropeanSpace agencylaunched its firstlunar robot probeSept. 28th fromFrench Guiana (erm,robots, space missions, and FrenchGuiana? Where do I apply?) The probe,SMART-1 (Small Missions for AdvancedResearch in Technology), is the first ofESA’s Small Missions for AdvancedResearch in Technology. Carrying sever-al miniaturized instruments, it's enroute to the moon using solar-electricpropulsion and a spiffy new ion engine.These incredible ion engines work simi-larly to rockets, but they fire out a pro-pellant gas much faster than the jet ofa chemical rocket — delivering about 10times as much thrust per kilo of propel-lant. Electric guns fire out chargedatoms, which is what gives the engineits "ion" name. SMART-1 will make thefirst comprehensive inventory of keychemical elements on the lunar surface,and investigate the theory that theMoon was formed following the violentcollision of a smaller planet with Earth.It will also search for ice — somethingeveryone hopes to find on the moon, asit is the key to colonizing the moon. Iguess Norton will have to start packing.http://robotics-society.org/servo/008

Photo courtesy of ESA

RRoobbyy tteess

SERVO 11.2003 63

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Windows, Mac, Linux, DOS, any RTOS, PalmOS, kernel,30 years experience, one-man shop, any size project, fast.

SCOTT @ ARTBOTS.COM

Robyte.qxd 10/9/2003 2:38 PM Page 63

64 SERVO 11.2003

courtesy of

NNNNovember is a busy month for robot competitors — withthe 24th annual All Japan MicroMouse Contest being the

biggest event of the lot. There are also contests being held byseveral of the major robot clubs in the US including CIRCand ChiBots in Illinois, and the DPRG in Texas. And onceagain, Texas A & M University will be hosting the annualstate championship for the BEST competition.

The first quarter of a new year is usually a bit slow butthere are some notable exceptions this year with the APECMicroMouse Contest scheduled for February in CA and themuch anticipated DARPA Grand Challenge coming inMarch. With a one million dollar prize, the DARPA event isshaping up to be one of the highest profile events ever forautonomous mobile robots.

— R. Steven Rainwater

NNNNoooovvvveeeemmmmbbbbeeeerrrr 2222000000003333

8 CIRC Autonomous Sumo Robot CompetitionPeoria, IL — This Central Illinois Robotics Club event will include an R/C robotic combat event in addition to autonomous sumo.

www.circ.mtco.com/competitions/2003/sumorules.htm

8-9 Olimpiada RoboticaCommercial Center Vizcaya de Medellin, Columbia— An annual maze-running contest.

www.upb.edu.co/automatica/olimpiada/olimpiada.html

9 ChiBots Robotics ContestSchaumburg Public Library, Schaumburg, IL — Events include basic and advanced line following,solaroller, and the amazing "Pound of Wood Mini-Sumo Challenge."www.chibots.org

15 DPRG Table-Top Robot Contest and Talent ShowDallas, TX — The last DPRG Talent Show was in 1999 — they don't happen often enough to miss!www.dprg.org/competitions

22 PAReX Autonomous Robotics CompetitionChallenger Learning Center, Phoenix, AZ —Autonomous Mini Sumo and Maze Solving. Mr. Ball is lost in the land of snakes and scorpions. Can your robot find him in time? www.parex.org/autoevent1.shtml

20-22 Texas BEST CompetitionTexas A & M University, College Station, TX — If your school doesn't have a team, check the website to find out how to get one started. www.texasbest.org or www.bestinc.org

21-23 All Japan MicroMouse ContestThe Panasonic Center, Tokyo, Japan — This is the 24th annual contest; 24 years of optimization have produced robots that can solve these mazes in 10 seconds instead of the original 10 minutes.

www.bekkoame.ne.jp/~ntf/mouse/taikai/taikai.html

DDDDeeeecccceeeemmmmbbbbeeeerrrr 2222000000003333

6 Boonshoft Museum LEGO Mindstorms Robotics CompetitionBoonshoft Museum, Dayton, OH — Localcompetition for the FIRST LEGO League. Winnersmove on to the state competition.

www.boonshoftmuseum.org/special_events.php3

6 Penn State Abington Robo-HoopsPenn State Abington, Abington, PA — Yes, this is autonomous robot basketball. Each robot has 60 seconds to make up to four baskets by shootingor dunking.

www.ecsel.psu.edu/~avanzato/robots/robohoops.htm

13 LEGO MY EGG-O Robotic Egg HuntGreat Lakes Science Center, Cleveland, OH —Bi-annual student contest of the Case WesternReserve University Autonomous LEGO RoboticsCourse.

http://www.eecs.cwru.edu/courses/lego375/

15-16 Eastern Canadian Robot GamesOntario Science Centre, Ontario Canada — In addition to the expected BEAM events, there's also a regional for the Trinity Fire-Fighting con-tests and autonomous sumo.www.robotgames.ca

JJJJaaaannnnuuuuaaaarrrr yyyy 2222000000004444

24-26 Yantriki TECHFEST 2004, IITBombay, India — This is a huge technical festival

Events.qxd 10/9/2003 10:54 AM Page 64

involving over 15,000 stu-dents from 750 colleges across India. There are a lot of other technical contests in addition to the robotics events.

www.me.iitb.ernet.in/yantriki orwww.techfest.org

FFFFeeeebbbbrrrruuuuaaaarrrr yyyy 2222000000004444

22-26 APEC MicroMouse ContestThe Disneyland Hotel, Anaheim, CA — If you can't catch the Japanese Micro-Mouse event, this oneshould be just as interestingwith some very advancedrobots.

www.apecconf.org/2004/APEC04_Home_Page.html

MMMMaaaarrrrcccchhhh 2222000000004444

13 DARPA Grand ChallengeLos Angeles, CA — The autonomous LA to Vegas cross-country, off-road, racefor a one million dollar prize. Not your average robot contest.

www.darpa.mil/grandchallenge

28 University of Florida Student Robotic CompetitionUniv. of FL Conference Center, Gainesville, FL — This is the only robot con-test you'll see where the robots are required to obey Asimov's three laws as part of the rules!

plaza.ufl.edu/niezreck/Robots_Competition_2004.html

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Events.qxd 10/9/2003 11:24 AM Page 65

SSo, you have this great robot that can follow a black linearound the room. You and I know this is a terrificaccomplishment, but it's lost on the non-practitioners

of the robotic art. They respond to robots on a far more shal-low level — like how much damage it can inflict, or if it's“cute” like R2-D2. Few onlookers will ever ask you "what doesit do" if your robot makes funny sounds or blinks lots of lights.

While not a construction material, and certainly not nec-essary to make your robot smart, lighting elements add styleand decoration to your robot. The right lights can make eventhe most boring line follower look cool. Lighting can also beused for practical applications. For instance, electrolumines-cent wire could be attached to the floor and used to preventa robot from wandering outside its perimeter. Or high bright-ness flashing LEDs could be used in multiple-player robot soc-cer. Ultraviolet lamps (and ultraviolet detectors, typically usedfor testing of paper money) could provide an optical proxim-ity system based on the fluorescence of materials.

In this column, we'll examine several popular types oflighting you can add to your robot. All arefairly inexpensive and can be purchasedlocally or through the Internet.

Super BrSuper Bright andight andSpecialty LEDsSpecialty LEDs

Light emitting diodes (LEDs) have beenaround for decades, but a fairly recent inno-vation is the super bright LED. These put outa bright beam that can be seen for hun-dreds, if not thousands, of feet. They're avail-able in just about every color of the rainbow,including blue and even white.

Visible light LEDs are classified by theirlight output, rated in candles (also calledcandela). Until recently, few LEDs producedmore than one candle, so the typical specifi-cation was in millicandles (mcd) — or thou-sandths of a candle. A 100 mcd LED pro-duces 100 millicandles — or 1/10 of a can-dle. Super bright LEDs, on the other hand,produce several candles of light. These maybe rated in candles or millicandles. For

instance, a 4,500 mcd LED produces 4.5 candles — that'sbright! And some are even brighter.

Color is obviously one feature to look for when shoppingfor super bright LEDs. You'll also want to compare the beamspread. The highest outputs are achieved by using a narrow10 or 15 percent beam, rather than the more typical 30 per-cent. For the latter, the LED may produce the same amountof light, but disperse it over a wider area. As a result, themeasured point intensity is lower. The brightest of the superbright LEDs are so bright they are painful to directly look at.So don't! In fact, they can cause the same sort of blind spotsas any high intensity light.

This is especially true of ultraviolet LEDs, which producelight at 400 nanometers, just below the visible spectrum. UVLEDs are typically used with fluorescent inks and dyes. Onmobile robots, limit their use to "undercarriage" lights toavoid the beam from pointing directly into anyone's eyes. UVlight is more interesting for what it does to fluorescing mate-rials, than as a direct light source.

Robotics Resources:

Lighting Effects

66 SERVO 11.2003

Find most any color LED at SuperBrightLeds.com

lighting effects.qxd 10/8/2003 10:58 PM Page 66

Cold Cathode Cold Cathode Fluorescent TFluorescent Tubesubes

Cold cathode fluorescent lamp (CCFL) tubes are com-monly used to “hop-up” personal computers with gloweffects. The light consists of the tube itself, plus a high volt-age inverter. Inside the tube is a coating that causes it toglow in any of several striking colors, as well as white andultraviolet. (Be careful of the ultraviolet tubes unless youknow it's safe — short wave ultraviolet can cause sunburn andblindness.) The inverter steps up the 5 to 12 volt battery volt-age to 100 or more volts, to light the tube.

CCFL tubes are available in different lengths. For roboticsapplications, the shorter 100 mm (about four inches) length isabout right. Another common length is 300 mm (about 12inches). If the tube is “bare,” you'll want to place it in a clear,rigid protective tube. You can purchase these at some homeimprovement stores, as well as specialty plastics outlets. Thetube helps prevent breakage and the possibility of small shardsof glass flying everywhere. If a rigid tube is not practical, clearflexible hosing, available at any pet shop that sells aquariumsupplies, is the next best choice. The tube may still break ifsomething strikes it, but the glass will remain inside the hose.

Use caution when handling the tube and inverter. Thoughthe current produced by an inverter is low, the shock isunpleasant, and it may cause you to recoil and drop the tube.

ElecElec troluminescent Ptroluminescent PanelsanelsElectroluminescent (EL) panels are used in products rang-

ing from nightlights to LCD backlights. The typical color is asoft green, but other colors are possible, including reds,oranges, and blues. Overlay filters can be used to alter thecolor, but the choices are limited. Electroluminescent panelsrequire a high voltage (90 volts or higher), and like the CCFLproducts, this is accomplished with an inverter. The invertersteps up the battery voltage to 90-120 VAC.

You can purchase EL panels as surplus, and experimentwith them. Look for panels with solid leads already attached;you can solder wires to the leads. Less useful are panels thatrequire a pressure connection to make electrical contact.These are harder to solder to.

The chaser panel kits sold by All Electronics offer a great

way to dip your toes into the exciting world of electrolumi-nescent panels. The kit includes an inverter, color filters, anda 3.75-inch by 1.7-inch EL strip that provides multiple connec-tion points. The strip can be cut into smaller pieces. Theinverter can power up to five separate strips, and provides 32pre-programmed lighting sequences.

ElecElec troluminescent Wiretroluminescent WireImagine a flexible neon sign — that's what EL wire is. EL

wire looks a lot like small plastic tubing, but when electricityis applied, it glows in a rainbow of colors. Here's how itworks: At the center is a solid copper conductor. This conduc-tor is coated with an electroluminescent phosphor. To excitethe phosphor, two very fine wires are wrapped around thecenter conductor. Covering this whole arrangement is a clearplastic sheath, which also protects everything inside.

Apply current to the wires and the phosphor lights up.Different colors are produced by varying the chemical make-up of the phosphor, altering the tinting of the plastic protec-tive sheath, varying the voltage, and/or varying the frequen-cy of the current driving the wire. The end result is a bright-ly colored glowing wire. EL wire has several uses in robotics.Here are just some of them:

•First and foremost, it looks cool! Wrap some EL wire ofdifferent colors around the periphery of your robot to give itsome pizzazz.

•Small strips of EL wire, of a certain color, can be usedto identify robots in a competition. If the robots are equippedwith filtered light sensors, they can even differentiate friendfrom foe on the battlefield.

•EL wire can provide illumination for the robot for use inobject detection. When used in conjunction with cadmiumsulfide (CdS) cells, the reflected glow of the EL wire can bedetected and used for proximity sensing. (In addition, manyred colored phosphors will emit a certain amount of near-infrared light, which is detectable with ordinary infraredphoto-transistors.)

•A strip of EL wire on the floor can be used for a linetracking robot. On the underside of the robot, affix sensorsto detect the glow of the wire.

•Strips of EL wire can be placed around the periphery of

by Gordon McComb

For Robotics

SERVO 11.2003 67

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68 SERVO 11.2003

a room or along the floor, to serve as a kindof electronic fence. Sensors on the under-side of the robot detect the light from the ELwire. A bonus: unlike a painted line, the ELwire can be switched on and off, therebyallowing the robot to exit the fenced area,should that be necessary.

EL wire is driven by a high voltage alter-nating current. But it need not be pluggedinto a wall outlet. Rather, the wire usessmall, self-contained inverters that producethe required voltage from a small DC source(usually 3 to 12 volts; AA batteries are suffi-cient).

Inverters are not terribly expensive —consumer models retail for $7.00 to $12.00.You'll have good results if you add moreinverters to drive additional strands of ELwire, rather than try to do it all from oneunit. Additionally, you can opt for an invert-er that blinks the EL wire at specific intervals,or keeps it on continuously. Specialty invert-ers are available with built-in sequencersthat, in turn, selectively activate severalstrands of EL wire. Note that inverters areavailable at different operating frequencies — from 400 Hz toover 12,000 Hz. The brightest outputs are provided at thehigher frequencies. The color of some phosphors can bealtered by changing the frequency of the AC excitation. Forexample, the “blue” phosphors can be changed from greento blue by varying the frequency between 400 and about6,000 Hz.

Color choice varies by manufacturer, but most offer thefollowing, in diameters from 1.3 millimeters (called “anglehair”) to 5.0 millimeters: aqua (blue/green), deep red, green,indigo (deep blue), lime green, orange, pink, purple, red,white, and yellow. The blues and greens tend to be the mostvibrant colors.

BodBody Jey Jewwelrelr yyLight-up body jewelry uses various types of LEDs — flash-

ing and continuous — electroluminescent panels and wires,and even Cyalume glowsticks. Glow-in-the-dark sticks can bepurchased at mall stores and even discount retailers such asWal-Mart. Look for a party shop, such as Spencer Gifts (mailorder and mall stores), for light-up body jewelry. For moreonline choices, try various Google.com searches:

•glowstick•rave lights•glow jewelry•magnetic LED earrings

Of particular interest are the LED earrings. Most use amagnetic backing rather than a piercing or clip. They're bat-tery powered and pulse in any of several colors. Colors vary— typical are alternating blue and red. You can attach the ear-rings to your robot using glue, double-sided foam tape, oreven with a flexible magnet strip.

LLasersasersLasers can be used for unusual and brilliant lighting

effects, as long as your robot will be used in a protected envi-ronment, without curious kids who might pick it up and lookinto the laser light. Laser pointers are battery powered, andrelatively inexpensive (many sell for under $10.00). The mostcommon color is red, but laser pointers in green and a fewother colors are available. Cost is considerably more for thelatter, as non-red laser diodes are more expensive to manu-facture.

You may opt to use the laser pointer as-is, mounting itdirectly to the robot. The on/off switch is spring-loaded, soyou'll need to work out a way to keep it depressed. Or, youcan remove the laser diode from the body of the pointer, andactivate it via a transistor or relay. Removing the laser diodeis not always as easy as it sounds, or even recommended —the metal barrel of the pointer acts as a heat sink. Withoutthe heat sink, the laser diode may prematurely burn-out. Youwill also need to provide regulated voltage. A limiting resistormay be needed to prevent the laser diode from pulling toomuch current from the robot's power supply.

Of course, the usual precautions of using lasers shouldbe observed. Avoid looking directly into the beam, and don'tallow the robot to be used in any situation where the beamcan accidentally point toward anyone — or any animal, forthat matter.

One idea for a laser-equipped robot is “light writing”using the open bulb setting of a 35mm film camera. Set the camera on a tripod, set the camera to “bulb” (the shutter stays open until you release it), turn off the lights, and let your robot loose. The laser will “paint” streaks of colored light on the film as it roams around theroom.

Coolight.com offers electroluminescent wire in a variety of colors and thicknesses.

S

lighting effects.qxd 10/8/2003 10:59 PM Page 68

All ElecAll Elec tronicstronicswww.allelectronics.com

All Electronics (local stores in Los Angeles, CA, cata-log mail order elsewhere) offers high brightness LEDs,electroluminescent panel kits (cut out shapes to makeyour own), CCFL lights, and high voltage inverters.

AS&C CooLightAS&C CooLightwww.coolight.com

Electroluminescent wire, inverters, and sequencers.Products can be purchased through their web page.

SSSSoooouuuurrrrcccceeeessss*

Fiber optics is an old technology, andit's easy to forget when planning lighteffects for your robot. But there's still plen-ty of life left in good ol' fiber optic lighting,and new technologies make it even moreexciting. Case in point: so-called “sideglow” fibers emit light over the length ofthe strand, not just the end. They lookmore like electroluminescent wire, but canbe made to glow any color, even alternatecolors.

Surprisingly, fiber optic strands suitablefor lighting effects can be hard to find.Most fiber optics sold these days are fordata transmission — expensive. Rather, youwant cheap fiber optic strands used tomake “fountain lamps” popular in the early1970s. Fortunately, a few retailers such asTarget and Spencer Gifts sell low-costreproductions of these lamps. You can yankoff the fiber and use it in your robot proj-ects. If you need longer lengths or a partic-ular style or type of fiber, check out FiberOptic Products, listed in the Sources sec-tion. They offer end glow and side glowfibers, lamps, bundles, fluorescent fiberoptics, and associated products.

FFiibbeerr OOpptt iiccss

SERVO 11.2003 69

Fiber Optic Products offers side glow fiber optic cable, similar in functionality to electroluminescent wire.

Gordon McComb is the author of the best-sellingRobot Builder's Bonanza and the Robot Builder'sSourcebook, both from Tab/McGraw-Hill. In additionto writing books, he operates a small manufacturingcompany dedicated to low-cost amateur robotics,www.budgetrobotics.com He can also be reached [email protected]

AAbboouutt tthhee AAuutthhoorr

Christmas is one of the best times to find unique lightingsystems for your robot. An increasing number of products aredesigned to run off low-voltage DC, so they're suitable forbattery-operated robots. Examples I've seen recently: mistle-toe that lights up when someone stands under it, a glowingSanta that speaks when someone approaches the front door,and chaser-light tree ornaments operated by two AA batter-ies.

Wait until after December 25th to get the good deals.Stores routinely offer unsold Christmas decorations at 50%off, or more. Same goes for the days right after Halloween.Though most Halloween lighting is in oranges and reds,they're a cheap source of LEDs, incandescent lights (strip offthe colored gel filters), and glowsticks.

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SSOURCESOURCES

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lighting effects.qxd 10/8/2003 10:59 PM Page 69

Black Feather ElecBlack Feather Elec tronicstronicswww.blkfeather.com

A cornucopia of unique electronics items: connectorsand cords, audio, gadgets, laser pointers, mini-cams, sol-dering, parts and switches, power, test equipment, kits,tools, video; high-brightness LEDs, and electroluminescentwire.

Cool Neon/FCool Neon/Funhouse Producunhouse Produc tionstionswww.coolneon.com

Cool Neon sells electroluminescent (EL) wire — a wirethat glows when subjected to high frequency supply volt-ages. Select colors and thicknesses, add a driver/inverter,and you're all set to go. Website includes some details onsoldering EL wire.

Don KlipstDon Klipstein's LED and Lein's LED and LaseraserInfInforormationmationhttp://misty.com/people/don

Everything you ever wanted to know about lamps, LEDs, lasers, and strobe lights.

ELELAM ElecAM Elec troluminescent Industrtroluminescent Industries,ies,Ltd.Ltd.www.elamusainc.com

ELAM is the manufacturer of many of the electrolumi-nescent wires sold under varying trade names (such asNeon Rim, Cool Wire, Live Wire, and Cool Neon). ELAM'sname for the stuff is LyTec. The company provides techni-cal details and specification sheets on the wire and invert-er/driver products.

FFiber Optic Produciber Optic Produc tstswww.fiberopticproducts.com

Fiber optics for lighting effects. Includes the tradition-al “end glow” fibers, where light goes in one end, andcomes out the other, as well as “side glow” fibers, wherelight is emitted through the shaft.

GiGilwlwaay Ty Technical Lechnical Lampampwww.gilway.com

LEDs and lamps. Specialty products include super-bright LEDs in all colors — from ultraviolet to infrared.

GloGlowirewirewww.glowire.com

Glowire sells electroluminescent wire in different thick-nesses and colors, as well as the necessary DC inverters usedto drive the wire. They also provide "laser LEDs," which are real-ly very bright colored LEDs. Useful if your robot needs brightheadlights.

J. AJ. A . LeClaire. LeClairewww.neontrim.com

Sellers of Neon Trim electroluminescent wire, inverters,and programmable sequencers.

Olmec AOlmec Advdvanced Matanced Matererials, Ltd.ials, Ltd.www.olmec.co.uk

Resellers and fabricators of specialty materials, includ-ing Surelight electroluminescent wire.

RepairFRepairFAAQ: Sam's LQ: Sam's Laser Faser FAAQQwww.repairfaq.org/sam/lasersam.htm

From Sam Goldwasser's RepairFAQ: Using and abusing(how not to) lasers. Includes a good section on safety.

Spencer GiSpencer Gi ff ts, Inc.ts, Inc.www.spencergifts.com

Spencer Gifts is a retailer of the unusual, including gagcards, joke gifts, adult novelties, and unusual lightingeffects (such as UV, fiber optics, and electroluminescent).You can order online, or visit a store near you. MostSpencer Gift stores are in fashion shopping malls.

Super BrSuper Bright LEDsight LEDswww.superbrightleds.com

Super Bright LEDs offers a wide assortment of highbrightness LEDs in a multitude of colors. Datasheets areprovided for all products. They also sell LED lamp productssuch as car running lights and “glow tubes.” Many of theseare applicable as attention-getters on robots, as well.

SurelightSurelightwww.surelight.com

Surelight sells electroluminescent (EL) wire in variouscolors and thicknesses, as well as EL drivers, light sticks,and other specialty lighting goods.

That's Cool Wire/Solution IndustrThat's Cool Wire/Solution Industriesieswww.thatscoolwire.com

That's Cool Wire sells electroluminescent wire and driv-er modules.

XenolineXenolinewww.xenoline.com

Xenoline sells electroluminescent and high-tech “glow-in-the-dark” products. This stuff is useful to “dress up” anotherwise boring robot, to provide a guide path or fence,or to provide illumination of a specific color for a robot withvision. Key products include:

• Xenopaks — Kits of different colored electrolumines-cent wire and driver circuits

• ZLine — Flat electroluminescent light strips (severalcolors in the orange to blue spectrum), 1/4” wide x 28”long

• Gamma Rays — Ultra-bright colored (blue, red,green, yellow, and white) LEDs intended as a light source

• Krill Lamps — Compact self-contained electrolumi-nescent “lanterns” in a variety of colors

• Laser pointers — Hack ‘em to make any pinpoint lightsource for your robot

70 SERVO 11.2003

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lighting effects.qxd 10/8/2003 10:59 PM Page 70

FORROBOTS

These days, robot builders are fortunate in that there is a hostof inexpensive and easily adaptablemobile robot base platforms available,and there are even more choices whenit comes to control electronics.Everyone has his or her favorite plat-form.

However, the choices are severelylimited when it comes to designing theactual programs that listen to sensors,control movements, and make deci-sions. A platform-independent methodfor designing control code would makeit much easier for robot builders toshare and expand upon previous work.That is what I hope to offer here.

We are interested not in howthings look, but in how things work.The most interesting structures we seeare living things. We want to build lifelike machines, and would like to knowhow they work. To do that, we need tounderstand sensors, brains, and

motors, since every animal seems tohave these. Also, we need to learnabout neurons, functions, trees, andnodes, as well as apply some algebraand computer science to the system.Building anything requires that youhave a tool set that is appropriate towhat you are working on. After welook at neurons, we will construct atoolset to define them.

Let's start with some brain factsthat are generally known. For example,we know that sensors, a brain, andmotors are attached to a body. Thereare many sensors, one brain, and manymotors. All living things, includingmicrobes and cells, have some varietyof this architecture. There is also a dataflow which requires "writers" and "read-ers." Data always flows from writer toreader:

Nature >> Sensor >> Brain >>Motor >> Nature

This shows the data flow and posi-tion of each of the elements of anyrobot or living being. It can also bevisualized as a circle with feedbackthrough nature. Sensors read nature,and a brain reads sensors. Motors readthe brain and act on nature, whichchanges what the sensors read. In liv-ing things, feedback is everywhere —from bottom to top.

Table 1 lists some common, obvi-ous brain facts or axioms. From thesefacts, we can deduce a purpose:

Brains mediate between sensors and a motor.

They are sort of impedance match-ers or transformers converting multipleinputs to separate outputs. A brain isthe total assemblage of neurons andincludes sensor and motor neurons.

There is no universal form for thisexcept as a list of transfer functions.

If a brain is the code, then neuronsare the hardware. Designing brainsrequires writing code. Building brainsrequires assembling neurons thatmatch the functions in the code. Anexample is given in Table 2.

From Fact 2, we can deduce thatthere must be a "least order" brain.Suppose there is no neuron. Whatdoes this mean?

Nature >> Sensor >> Motor >> NatureThis is the resulting data flow.

Note that sensor and motor are singu-lar here. From this we deduce that abrain is needed when sensors aregreater in number than the number ofmotors.

A neuron is needed for mappingmultiple inputs to an output. Since aneuron is a function, we can write anequivalent function on paper and buildit in hardware. If we can make a neu-ron, we can make a brain.

We need some tools to write braincode. I call my tool set "Hal Algebra." Inlife, neurons form upside-down treeswith many inputs leading to an output.In Hal Algebra, we'll call these HalTreesand we'll call neurons nodes. There areseveral types of nodes.

I use long variable names and tryto flow the math into the language. If Ihave a variable name that is plural,then that means there is more than

Fact 1:A brain is always between

sensors and motors.

Fact 2:Brains are of different sizes.

Fact 3:Brains are constructed of

neurons.

Fact 4:Neurons have synapses and a

single axon.

Neuron[j] = f(synapses[j]); from fact 4

Brain = Neuron[1]...Neuron[n]; from fact 3

SERVO 11.2003 71

NEURONS

by Harold Reededited by Chris Hannold

Table 1

Table 2

neuronsforrobots.qxd 10/10/2003 6:16 AM Page 71

one item attached. The math is basedon simple algebra and the operations + (Add), - (Subtract), * (Multiply) and /(Divide). Ultimately, we will turn equa-tions into machines. Equations have asingle output, and one or more inputsseparated by operators. A = B + C is ageneral example. A is the output of B +C, where B and C are inputs and + isthe operator.

Z = f(X,Y) says that for every valueof X and Y there is a value for Z, basedon the function f. Z is the output, andX and Y are inputs. Functions will alsobecome machines.

So far, I have made these func-tions, or nodes, shown as a table. "I"stands for Input, "R" is a second input,and "O" stands for Output. SNodes canbe tree nodes and switches (IF-Then-Else for you code hounds). TNodes aresingle nodes that perform a complexfunction. Refer to Table 3 for a list.

Table 4 lists some similarities ofneurons and HalTrees. There are also

differences, of course. In the table, N isany counting number, c is node cycletime, L is column level, and S is thenumber of inputs.

There are some differences, mostlyin favor of HalTrees:

1. HalNode headers connect tightlyto data cable plugs. Neurons axons andsynapses connect loosely and wetly.Global acting, hormonal-like actionsare explicit in the brain code, that is,they must be programmed in.

2. The insides of neurons cannot beaccessed. HalTrees can be accessed atany and every node.

3. Neurons can change their internalcode based on input information. Thedesigner of HalTrees must change codeby rearranging connections based onexperience. Headers make this possiblein hardware.

The property of trees that allowsus to measure size is the number ofinputs the tree has. To make a largertree, combine it with or add it to anoth-er tree. To make a smaller tree, takeaway some of the tree. Trees obey therules of arithmetic:

Tree A = Tree B + Tree C

If you have a tree with B inputsand you add a tree with C inputs theresult will be a tree with B + Cinputs.This means that on your robot,you can start at a motor and build theneuron tree at will, expanding as yougo. You can start with a two-input treeand end with a hundred-input tree byadding one node at a time. To add anode, open up a header and plug inanother node or tree.

The only software you need tochange is the brain's neuron list. Thereare many possible tree architectures, asyou might have guessed. Here, we willignore size and instead look at theshape. Here are a few examples usinga Cnode at the motor (O is the differ-ence of I,R). By now you should be visu-alizing data pouring into the inputs,and streaming out of the output in theexamples:

• Command trees collect do's anddon'ts for a motor:

Doing = Do - Don't

• Information trees collect directionfor a motor:

Direction = Left - Right

• Collection trees gather informationfrom sensors:

Touched = touchedLeft - TouchedRight

• Property trees collect object prop-erties:

animal = living + being ; 2 = 1 + 1man = rational + animal ; 3 = 1 + 2rational = man - animal ; 1 = 3 - 2

Operator HalNode Notation DescriptionTree nodes SNodes- CNode O <= I - R O is the difference of I,R+ PNode O <= I + R O is the sum of I,Ro ONode O <= I o R O is the Max(I,R)a ANode O <= I a R O is the Min(I,R)> GTNode O <= I > R O is I if I > R else 0< LTNode O <= I < R O is I if I < R else 0is ISNode O <= I is R O is I if I = R else 0

Single nodes TNodesi INode O <= I(I)-R O is integral of Id DNode O <= d(I) O is derivative of I f FNode O <= f(I) O is frequency of In NNode O <= n(I) O is 0 - Ib BNode O <= b(I) integer -> offset binaryNot NotNode O <= I) If I = 0, O = 1 else O = 0

Switches SNodesg GNode O <= I g R O is R if I > 0 else 0l LNode O <= I l R O is R if I < 0 else 0z ZNode O <= I z R O is R if I = 0 else 0

Property In a neuron In a HalTree

Data flow Synapses >> axon Inputs >> outputInput size 1 to N 1 to NData size >= 2 bits >= 2 bits (8 bits now)Cycle time t=(S-1)*c t=(S-1)*cFan out SL-1 SL-1Functions varied See Table 3

72 SERVO 11.2003

Table 3

Table 4

neuronsforrobots.qxd 10/9/2003 3:14 PM Page 72

SERVO 11.2003 73

Of course, there is more to this —several books more, but like every-thing, it starts simply. Your brain cangrow as the complexity of your robotgrows. Since code must be easily mod-ified, I would also make the hardwareeasy to modify by providing easy con-nections with headers and sockets.

We can make nodes of sensorsand motors. Let I, R, and O be headerson the nodes.

Carry the data flow on cableswith plugs that plug into the headers,and you have the machinery of thedata flow captured. Nature plugs intosensors, which plug into a brain,which plugs into motors, which movenature. Any computable equation orfunction can be made into hardwarethis way.

From now on, when you see anequation, also see the inputs, output,the program, and the connections.

• -, +, o, a, >, <, is, g, l, zare operators• Not, n, d and i are functions• <- is a data flow indicator

(here from right to left)• = is the transfer operator (it

may be read as "becomes")• ; is a comment delimiter

Sensors read nature and writedata streams:

Sense -> Output

Definition: Sensor writes a datastream.

Nature -> O ; is the equation

Here is some pseudocode for asensor:

Sensor:Read a property of natureConvert it ; Light intensity to numberWrite to OGo to Sensor: ; Do this forever

Here, the motor reads a datastream and writes to nature:

Input -> ActionDefinition: Motor reads a data

stream.

I -> Nature ; is the equation

Here is some pseudocode for amotor:

Motor:Read IConvert it to an action ; run CW, CCWWrite it to natureGo to Motor: ; Do this forever

Any sensor can connect to anymotor with a data stream cable. Sensor

-> Motor. The data stream cable canhave any name. We say ThisMotor =ThatSensor. That means ThisMotor ispasted on the motor input I, andThatSensor is pasted on the sensor out-put header O. Anywhere there is aheader, a data stream socket can con-nect. Data streams carry information.

This month, you were introducedto Hal Algebra as a way to design neu-rons for robots. Neurons are simplyfunctions that can be modeled bymathematics. I gave several examplesof simple neurons and showed howthey can be used to describe theactions between sensors, motors, andthe robot's environment.

In a future article, we'll cover a fewmore functions and start combiningthem into HalTrees. Finally, we'll put allthis knowledge to use by designing abrain for a simple microbe living in apond.

S

ABOUT THE AUTHORYou can learn more about Harold L.

Reed's work at his website,wwwwww.halbr.halbrain.comain.com and he can be

reached at [email protected]

neuronsforrobots.qxd 10/14/2003 11:02 AM Page 73

What WouldYou Trust A

by Jeannine Gailey

Dr. Ernest Hall builds robots that learn

from their mistakes. Adapt or perish!

74 SERVO 11.2003

Gailey.qxd 10/7/2003 11:25 AM Page 74

??Robot To Do?On any given Saturday this summer at the University of Cincinnati,

you will find Dr. Ernest L. Hall, Director of the Robotics Center, in

the robotics laboratory with a dozen or so students, eating pizza and

comparing ideas for their robot, the Bearcat (named after University

of Cincinnati's team mascot), which will be competing in the

Intelligent Ground Vehicle Competition in 2004. The students are from

graduate and undergraduate programs as diverse as mechanical,

industrial and electrical engineering, computer science, and

psychology. Dr. Hall, who recently won an Innovative Teaching award,

has spent 20 years giving students the opportunity to apply the

theory they learn in his classes by designing and building a robot that

is capable of guiding itself through an obstacle course.

Dr. Hall is interested in robotics, but also interested in the

practical application of engineering design, artificial intelligence

theories, software and hardware programming, and plain old mechanical

ability. And he wants to make that application fun. That is why

students are willing to give up their free time to work in the lab

building and programming a robot that can gather information about its

surroundings, make decisions, and physically master a series of

challenges. This isn't your average Radio Shack robot made for a quick

derby battle, content to be driven by a person with a remote control.

In many ways, it is a thinking machine.

SERVO 11.2003 75

Gailey.qxd 10/7/2003 11:27 AM Page 75

Why IntelligentRobots?

You can see the potential forthousands of applications — robotsthat could navigate a street with-out running over pets or crashinginto other objects could performroutine duties such as street clean-ing or trash collection. Such robotscould also perform risky bloodwork in a medical lab, or take thestrain off overworked hospital staff by doing tasks like deliv-ering meals to patients or collecting soiled laundry. Whatwould you trust a robot to do? This is a key question, Dr. Hallpoints out, one that both defines and limits the goals ofrobotic researchers. If a robot is developed that could admin-ister vaccinations, would people trust a robot to do that? But,if the robot could be trained to perform janitorial duties at anuclear waste site, and this eliminated risk to human life,would people be more willing to trust it then? The practicaladvantage of robots that can learn is in allowing robots totake the place of humans in dangerous situations, whichmeans having robots that could detect and avoid land mines,or collect hazardous materials at a Superfund site withoutcontaminating safe areas.

Dr. Hall, who has written three books and hundreds ofpapers and articles on machine intelligence, knows that theidea of an intelligent robot may sound pie-in-the-sky. But hepoints to examples of intelligent robots that are already inthe workforce — the robot lawn mower, robot vacuum clean-er, robot food delivery system and robot helpers for the elder-ly. Unmanned military ground, underwater, and aerial vehiclesare currently beind developed at an accelerated pace as well.

What is Machine Intelligence?Alan Turing is often thought of as one of the "fathers" of

Artificial Intelligence, the science of creating intelligent com-puters. As early as 1947, he believed machine intelligencewould be found in the ability to communicate with naturallanguage. Some "bots" on the web are now savvy in the nat-ural language department. In the 1970s, research into artifi-cial intelligence moved towards creating machines that couldrespond to visual stimuli, and some scientists tried to repli-cate the data manipulation of the human brain, buildingmachines with neural networks.

Dr. Hall defines machine intel-ligence as requiring two attrib-utes. The first is the ability to reactto sensory information. "We havebeen doing this for twenty years,"he says. Examples of this todayinclude AIBO, the robot dog fromSony that has the ability torespond to sound, touch, andvisual stimuli. However, AIBO can-not learn. "The other, more chal-lenging, aspect of machine intelli-

gence is creating a computer brain that can learn from repeti-tive actions." With his students, Hall has been studying neuralnetworks in robots — that is, an architecture in which com-puter processors are interconnected similarly to the way neu-rons connect in a human brain. This system allows the com-puter to learn by a process of trial and error. "We need to bemore patient with our robots," Hall says. "Giving them timeto learn may mean exposing them to not hundreds but thou-sands of iterations over time." More advanced ideas aboutneural networking have emerged recently - for instance, theideas of the adaptive critic and creative learning.

Dr. David Casasent, a professor of electrical and comput-er engineering at Carnegie Mellon University, and also aresearcher in the area of optical systems, has worked with Dr.Hall for over 20 years. "When we started the SPIE IntelligentRobotics and Computer Vision Conference, vision guidedrobotics was just a research idea. Now we have several of theseideas put into actual practice, such as the Sojourner that is onMars, and many vision-guided robots in industry and defense."

Q/A With Dr. HallJGJG: What is this adaptive critic learning?DrDr. Hall. Hall: The adaptive critic is a form of reinforcement learn-ing that was developed by Paul Werbos of the NationalScience Foundation (NSF). It uses a back-propagation algo-rithm of a neural network to distribute error through the net-work network and make the adjustments needed to learn agiven goal. In robotics, it can be used, for example, to makea robot follow a precisely specified path.

JGJG: How would you define creative learning and how is thisapproach different from existing techiques in machine intelli-gence?DrDr. Hall. Hall: Creative learning chooses one of several goals - this

Want to Know More About Intelligent Robots??Web Sites of Interest:

wwwwww.r.robotics.uc.eduobotics.uc.edu - The University of Cincinnati's Robotics web pagewwwwww.igvc.org/deplo.igvc.org/deployy - The Intelligent Ground Vehicle Competition web page

wwwwww.auvsi.org.auvsi.org - The main sponsoring organization for the University of Cincinnati robot teamwwwwww.ai.mit.edu.ai.mit.edu - MIT Artificial Intelligence Lab site

http://vhttp://vasc.ri.cmu.eduasc.ri.cmu.edu - Carnegie Mellon's Robotics Institute's Vision and Autonomous Systems centerwwwwww.aaai.org/P.aaai.org/Pathfinder/index.htmlathfinder/index.html - A Web site of the American Association for Artificial Intelligence

76 SERVO 11.2003

Gailey.qxd 10/7/2003 12:13 PM Page 76

is the creative part. Once a goal is selected, the adaptive crit-ic can be used to let the robot achieve it. This approach hasone higher level of control than the adaptive critic alone.

JGJG: Tell me a little bit about the robot that you are design-ing to test creative learning.DrDr. Hall. Hall: We have designed the hardware of the BearcatCub, a small modern version of our existing Bearcat robot. Ithas a hybrid power source that will generate electrical powerfrom a small, quiet gas engine. It also uses Segway™ hightraction wheels and gearboxes. It also has a web-based Galil™motion controller and will be run from a Dell laptop. We arealso designing creative control and learning software for it.

JGJG: How does the robot you are working on display decision-making abilities?DrDr. Hall. Hall: The robot's program employs decision makinglogic. It starts by following a line on the ground. If an obsta-cle is encountered, it must go around, and then return to linefollowing. If the line disappears, it looks on the other side ofthe path for it.

JGJG: So, which type of creative learning or machine intelli-gence does the robot you take to the contest display? Andwhat makes your robot different or more intelligent than, say,the robotic vacuum cleaner that's now commercially available?DrDr. Hall. Hall: The type of machine intelligence programmed intoour robot for the contest is goal accomplishment with adap-tation. That is, during the line following (autonomous chal-lenge) part of the contest, the robot's goal is clear: go thelongest distance in the shortest time. It is even given lines tofollow. However, along the way there are obstacles to avoid,a hill to climb, a sand trap, an asphalt section where the lineschange colors and portions where the lines become dashedand disappear. Adapting in real time to all these changingenvironmental conditions displays one form of machine intel-ligence. In the navigation part of the contest, the robot isgiven waypoints that mark locations on a map. However, itmust first determine which waypoint to go to and still avoidobstacles along the way.

Finally, in the follow-the-leader part of the contest, therobot must follow a human driven vehicle at a given distanceeven when the leader vehicle turns, speeds up and slows down.Each of these adaptive behaviors show a little intelligence.

Certainly, the exploration into intelligent robots thatUniversity of Cincinnati's Dr. Hall and his team exemplify what ishappening at other colleges in the United States, from MIT andCMU to the more far-flung reaches of Japan, Wales, andFinland. With increased interest and funding, and more every-day applications being solved, these programs will soon be thebirth place of the next generation of decision making robots.

AUTHOR BIOJeannine Gailey, who has worked at Microsoft, IBM, and AT&T, is

currently a consultant and writer whose book on XML WebServices is debuting this fall from Microsoft press. You can learnmore about her work at wwwwww.w.webbish6.comebbish6.com, and she can be

reached at [email protected].

Behavior-BasedRobotics (Intelligent

Robotics andAutonomous Agents)

by Ronald C. Arkin

Mobile Robots:Inspiration to

Implementationby Joseph L. Jones and Anita M. Flynn

Mobile Robotics: APractical Introduction

by Ulrich Nehmzow

Artificial Intelligence:Modern Approach

by Stuart J. Russell andPeter Norvig

Atificial Intelligence and Mobile Robots: CaseStudies of Successful

Robot Systems Edited by David

Kortenkamp, R. PeterBonasso, and Robin

Murphy

Sensors for MobileRobots: Theory and

Applicationby H.R. Everett

Hanbook of IndustrialAutomation

Edited by Richard L. Shelland Ernest L. Hall; Hallalso wrote Computer

Image Processing andRecognition

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SERVO 11.2003 79

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Vol. 1 N

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vemb

er 2003

0 474470 58285

11>U.S. $5.50 CANADA $9.25

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