Build Your Own Copter Part2

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http://www.diydrones.com/forum/topics/build-your-own-copter-part-

ii?xg_source=activity&id=705844%3ATopic%3A1412973&page=1#comments

http://www.scoutuav.com/

http://copter.ardupilot.com/wiki/build-your-own-multicopter/

Build Your Own Copter - Part II

Posted byForrest Frantz on September 20, 2013 at 5:47am inUnassigned category

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Round tubes are back.

The goal of this build has various missions:

1) show how easy it is to build a ship on par with commercial ships.

2) stay aloft for over 30 minutes carrying a full-size camera.

3) use low Kv motors and low voltage to create an efficient ship but stable camera platform (a design that is usuallycontrary to the objective).

4) fly at slightly less than 200 Hz but also be able to fly at 200 Hz (the evil frequency) to test the impact of doing that

when vibrations are only managed by frame stiffness and low mass.

5) test light methods to mitigate the more fragile cloth/woven carbon tubes.

6) test APM code flexibility on flying a new octa motor layout.

After a successful test using braided carbon fiber tubes that are basically indestructible, strong, stiff, light, and provide

surface that is easy to bond, this discussion will focus on using cloth or woven carbon fiber tubes. Relative to braidedtubes, woven tubes have a smooth surface (not as easy to bond), have a lower resin content, and layered fibers. Braide

tubes use fibers that are braided from the inside layer to the outside layer. Woven tubes stack and bond either cloth o

tape layers placed in multiple directions to derive engineered stiffness and light weight. But unlike pultruded (where

most all fibers in one direction), there are axial fibers to keep cracks from propagating. Why not just stay with braided?

Woven carbon tubes are more available, come in more sizes, and are lighter for their stiffness.

This discussion will go from design through flight tests.

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Permalink Reply byForrest Frantz on September 20, 2013 at 6:56am

Installment 1: Requirements.

Set some measurable criteria for your ship. For this ship, mine were:

o An 80 degree clean (no props) field of view for a camera sensor located at the ship geometric center (full size camera

o A 120 FOV with the camera sensor located less than 7" forward of center (go pro) for pan 90 degree downward to

forward to 90 degrees upward.

o Total frame weight (bolts, masts, spars, platform, gussets, ties, etc.) < 400 grams to derive

- stiffness resulting in x/y/z accels < .1g

- not fail at 9 gravities x 3.2 kg (approx max ship load)

o Land safely with any 1-motor failure (octa?)

o Rotors with > 2 x 2.3 kg net-thrust (thrust after lifting themselves) or 575 net grams thrust per rotor

o APM located at center of x/y CG and positioned at the propeller z-plane.

o Able to backpack.

o Able to assemble in field in < 12 minutes.

o Flight time with GoPro of > 30 minutes.

o Ability to support gimbal for high quality stills and videos.

o 140 Hz < hover frequency < 180 Hz.

Reply

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Permalink Reply byForrest Frantz on September 21, 2013 at 9:39am

Installment II: Preliminary Design

Preliminary design can be as simple as looking at your desk top and just saying, "I'm going to try to meet my

requirements using stuff in this pile." Or it can be as time consuming as spending a few years or so testing motors,

props, ESCs, batteries, structures, controllers, wiring, build methods, landing gear, camera gimbals, vibration systems,

radios, etc.

So confession time. I did the latter and still have a long way to go ... learning every day thanks to patient bloggers and

friends.

To meet requirements, weight and lift efficiency were the two biggest factors. A year of research bore out the followin

gains:

1) Rotor (motor, prop, mounts) net-lift to mass improvement of 30%

2) Structure (frame, platform, fasteners) 120 gram improvement

3) Electronics (components and wiring) 35 gram improvement

4) Batteries net duration to mass improvement of 3%

Rotors: When through a list of over 2,000 motors comparing previous test results. Then bought what appeared to be

the best for test.

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For the test also bought an assortment of propellers for each of the motors ( ... so a lot of combinations).

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Made a multicopter test frame to measure watts and lift. Then tested based on net-lift per watt. Testing formulticopters is different than testing for planes. A rotor has to lift itself first before it can benefit the rest of the ship,

hence net-lift. Obviously too, a larger prop takes more structure, so the rotor has to also lift additional frame mass (fo

my builds about 2 grams per inch per rotor for props over 10"). In any case, to make a long story short, I ended up

chosing an RCTimer HP4215-460KV motor with an unidentified 15 x 5.5 Carbon prop I found in China. I went for the

460KV range to get the natural frequency of the ship just below 200 Hz during hover to meet that particular

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requirement. Is this combination the optimal rotor? Heck no. Every time I think I have the best showing huge

improvements, someone comes along and recommends something else. Right now Hugues has me looking at T-Motor

Structure: Bought about every wood, aluminum, and carbon piece of structure out there (even archery arrows). Teste

for durability and stiffness to weight. From flying kites knew that pultruded carbon sucked, so ended up focusing on

wrapped, braided, and cloth carbon tubes. Ended up with three potential tubes to be used in the design process, eachideal for different loads and lengths. From left to right:

o Braided carbon tube - 11mm OD 100% strength factor 0.87 g/cm (indestructible)

o Fabric carbon tube - 15mm OD 102% strength factor 0.69 g/cm (moderate lengths and weights)

o Wrapped carbon tube - 22mm OD 253% strength factor 0.84 g/cm (long lengths and higher loads)

Platform: The lightest/strength material out there for platforms is what you walk on when you fly - carbon sandwich

panels. A few of my patents were based around the use and optimization of these materials on Boeing and Airbus

aircraft. The downside is that these materials are expensive. But they are avialable. This panel is a 1/4" thick single pl

carbon sheet on top and bottom that sandwiches a Nomex core (hex expanded epoxy impregnated paper).

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Controller: APM of course. The open source makes custom copters possible. And a fantastic set of intelligent and

knowledgeable developers that are willing to share.

ESC: Haven't done a lot of work in this area so just used one that works with APM. Was drawn to the MDrive because

you could program the precise advance timing and optimize efficiency. But APM didn't work with them.

Wiring: The lightest wire I found was UL AWM Style 1429. The sheath is UV protected and thin (light). But it's not easy

to find. So pay attention to the amount of plastic on the wire. You don't need much. The copper itself obviously need

to be appropriately sized in the design process to make the ESC to motor runs.

Gusset Material: Chose 0.060" fiberglass for structural plates (motor mounts and motor-mast to platform plates.

Couldn't find a carbon sheet that cut nice. Chose 0.040" fiberglass for edging members to protect the sandwich panel

from edge loads (e.g., where the zip ties go through the panel.

Joining System: Nylon bolts, washers, and nuts; UV rated zip ties; high-shear & peel strength epoxy adhesive.

Legs: Pool noodles or pipe insulation.

Batteries: Some weight can be saved on batteries. The weight of a LiPo is dependent on the core material, plastic/tap

wrap, wire, and connectors that change as the battery size increases. If you can choose the lower C rated batteries you

will save some weight. Within the same manufacturer, there is an optimal battery size (found by taking the actual

weight / capacity. For Turnigy, it was the 3S 3000 mAH battery (this might have changed with their new batteries). If I

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fly with four 25C batteries, I was able to use the lowest C rating. This area has room for a lot of weight savings but

haven't had time to investigate more that that.

So with those limitations imposed on myself to meet the requirements, it's now time to design the ship.

Reply

Permalink Reply byForrest Frantz on September 22, 2013 at 11:52am

Installment 3: Design

The APM is extraordinarily flexible. It can handle motor layouts that deviate from regular polygons (for example all of

the designs below). So the question for me was, which irregular polygon shape leads to the lightest weight and stiff

frame? To do this I used an Excel based CAD system that evaluated the following Variant shapes--the primary criteriabeing the mass of the structure required to support that shape.

First the regular octagon. Stable platform but no field of view. It's also heavy. The CAD system calculates the weight o

the black lines, which represent the motor masts.

The first morph was the U with a wide open front. Now we can meet the FOV requirement. But as this ship is morphe

to a wide enough FOV, it weighs too much even when the masts are optimized into a V-crosshatch layout.

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The fourth morph was the 8--8 and variants of it (other free-form shapes not shown). The 8--8 is really getting light, bu

I was not comfortable yet with a mast bonded to another mast only in one spot. I planned to crash a lot and needed

something that would survive.

So settled on the X2.

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The video shows the CAD system morphing design until the optimal weight is found that meets the requirements.

https://www.youtube.com/watch?v=cziCwCuCCb0&feature=youtube_gdata

Tomorrow it gets fun ... I start the build.

Reply

Permalink Reply byForrest Frantz on September 27, 2013 at 8:15am

Propellers at Different Levels? Does it matter. Was asked this question. So am putting the question out there for

comment.

History: There are many commercial examples of helicopters with multi-rotors at different levels.

www.airliners.net/aviation-photos/small/6/3/0/1336036.jpg" alt="Photo ID: 1336036 Views: 14628 UK - Air Force

Boeing Chinook HC3 (352) (ZH898) shot at Off-Airport - Salisbury Plain Training Area UK - England March 7, 2008 By Kar

Drage - Global Aviation Resource"/>

Reasons: Better prop tip separation (less noise/cleaner air).

Impact on lift: None to my knowledge

Impact on control: Let's go to extremes. Take two sets of rotors 10 meters apart: two on the same level and two

stacked on top of each other. For the two at the same level you roll capability. For the two stacked on top of eachother you have no roll capability. For the same level case, as air varies around each prop, roll can be induced creating

instability. For the stacked, roll isn't induced so the ship remains stable. So from an extreme point of view, do you wan

stability or roll/pitch response?

Mathematical difference: This is all controlled by the aspect ratio of the propeller plane. With a 'same level' design, th

aspect ration of height to width is zero. The aspect ratio of the X2 is .023 or a 2.3% difference in roll and a 4% differenc

in pitch. This would have a small impact either way on increased stability or decrease in roll response. However, if this

was an acro machine build for competition, then I'd look hard at a different frame approach that puts all the motors at

the same level. The X2 is built for photography.

Reply

Permalink Reply byForrest Frantz on September 23, 2013 at 12:53pm

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Installment IV: Design Validation and Fabrication

Do these two steps in parallel. Validating design is making prototypes of complex stuff like the electronics platform an

making sure everything fits. But some of the parts are simple, like the motor mast. So just make them.

Step 1: Tape a full-scale print out of the design to the floor. There are CAD systems for free that will do this and other

that don't cost much that also will create cutting profiles for 3-axis CNCs for the mounting plates and gussets. Make

sure that the floor location chosen is flat.

Step 2: Tape the corners of the mounting plates to the design. Avoiding putting tape where the adhesive goes. Put tap

where you don't want the adhesive to go.

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Step 3: Tape a tool to the floor to hold the motor mast in place while the adhesive is curing (the little bars at the end of

the motors masts taped to the floor with duct tape).

Step 4: Mix the adhesive. Stir it well as this determines how well it cures. Shown is Hardman Orange that has high

shear strength and peal strength and OK temperature resistance. Another choice would be 3M Scotch-Weld EC 2216.

The Orange comes in a double bubble pack that you fold in half, cut, and the two parts come out on top of each other

nice and neat and ready to stir on supplied wax paper pads (they also supply the stir sticks).

Step 5: Apply a 3mm or so tall bead down the center of each of the plates (motor mount X plates and motor mast to

electronics platform plates) that go on the same side of the motor mast.

Step 6: Carefully locate the round motor mast tube onto the beads. Rotate the motor mast back and forth around 12

o'clock (from 11 to 1 o'clock) so that the adhesive can bond to a larger area on the motor mast. Check that there is an

even application of adhesive to the tube and plates and that the outer zip tie holes are free of adhesive.

Step 7: Tape the tube to the holding tools. Place weights onto the tube. Let cure over night.

Step 8: Remove that motor mast and do the other motor mast. Let it cure over night.

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Step 9: Flip the motor mast over that has plates on both sides (one will have plates only on one side; see photo below

Repeat the bonding process for those plates except this time make sure the weights on top of the motor mast hold the

top plates parallel to the bottom plates. An easy way to do this is repeat the clearance to the floor (the part of the

motor mast that was cut off plus two fake plates) and balance the weight using this spacer. Let cure over night.

Step 10: Cut out the electronics platform from something temporary like thick cardboard.

Step 11: Get some inexpensive 8" zip ties.

Step 12: Assemble the ship onto the electronics platform using the zip ties.

Step 13: Assemble the wire jungle onto the prototype platform.

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o holes for zip ties used to tie down battery wires

Step 15: Cut out the electronics platform. In this case, the electronics platform is made from single play carbon 1/4" 2

pound Nomex core sandwich panel. On an aircraft, you primarily walk on double carbon ply .4" floor panels that have

higher density core.

Step 16: Bond the reinforcement plates to the electronics platform. A single ply of carbon won't handle side loads fro

small objects like zip ties pulling the motor masts against the platform (zip ties segments are temporarily used to align

the plates over the holes during cure) or the Velcro strapped around the batteries (the small rectangular plates). 0.040

fiberglass plate is adequate. Do one side. Let cure for 3 hours. Flip it over and do the other side and let cure over nigh

Step 17: The plates take little adhesive. Use the rest on the ends of the motor masts. Put small beads of adhesive on

the inside and outside of the carbon ends to help keep the ends together during a crash. This will help keep single

strands or tows will pealing away from the rest of the laminates. It would be best to bond a round cap made from 0.06

fiberglass to each end. During final assembly, we will also bond a small piece of foam to further protect the ends. Let

this cure over night.

To summarize, this can take a few nights of cure time. But while its curing, you can study up on the hard stuff, like the

electronics.

Tomorrow we do final assembly and integration.

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Reply

Permalink Reply byForrest Frantz on September 24, 2013 at 11:23am

Installment V: Final Assembly

o Zip Tie the platform to the motor masts.

o Mount all the electronics to the platform.

- APM in this case is directly bolted to the upper motor mast at one end and the platform at the other end.

- Radio receiver is zip tied with the control wires separated from the DC voltage wires. Antenna is pointed forward.

- All wires are zipped tied to the platform with adequate strain release loops.

- Control wires that cross DC wires are crossed at right angles.

- Ratio satellite is zip tied to the platform. Left antenna points left. Right antenna points down.

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o Balance the props Axial - This is done as you've seen many do before using readily available prop balancers. On

carbon props, add tape as needed near the tip. Do not sand the blade as this can wear through the Epoxy and expose

fibers.

o Balance the props Planar - Mount the prop onto the motors. Lightly tighten the prop. Spin the prop by hand and

measure the distance from the ground at two opposite points. Make sure that both blades tips trace the same path.This is the largest source of prop vibration. On carbon direct mount props, you can usually just tighten the prop on the

high side more to bring the blade down. Sometimes with other types of props, you can simply rotate the blade to a ne

position under the nut and see if that helps. If not, remove the prop and appropriately sand the mount area.

That was a good day. Tomorrow we integrate (make the firmware fly this puppy).

Reply

Permalink Reply byForrest Frantz on September 25, 2013 at 4:49pm

Installment VI: Integration

Today we load the custom firmware for this unusual motor layout.The reality is that loading custom software is as easy

once the basics are complete, as loading standard firmware.

1) Create a personal work space for the APM code on your computer (for details, see attached).

2) Download the software to that workspace. Currently the code resides

athttps://github.com/diydrones/ardupilot/tree/ArduCopter-3.0 (for details, see attached).

3) Find the source code that needs to be modified. Look under the Ardupilot-ArduCopter-3.0>libraries>AP_Motors

directory for the appropriate file. In this case, for an octa, the file is AP_MotorsOcta.cpp. In that file you will find the

paragraph of code that discusses a V(ariant) frame:

}else if( _frame_orientation == AP_MOTORS_V_FRAME ) {

// V frame set-up

add_motor_raw(AP_MOTORS_MOT_1, 1.0, 0.34, AP_MOTORS_MATRIX_YAW_FACTOR_CW, 7);

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add_motor_raw(AP_MOTORS_MOT_2, -1.0, -0.32, AP_MOTORS_MATRIX_YAW_FACTOR_CW, 3);

add_motor_raw(AP_MOTORS_MOT_3, 1.0, -0.32, AP_MOTORS_MATRIX_YAW_FACTOR_CCW, 6);

add_motor_raw(AP_MOTORS_MOT_4, -0.5, -1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CCW, 4);

add_motor_raw(AP_MOTORS_MOT_5, 1.0, 1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CCW, 8);

add_motor_raw(AP_MOTORS_MOT_6, -1.0, 0.34, AP_MOTORS_MATRIX_YAW_FACTOR_CCW, 2);

add_motor_raw(AP_MOTORS_MOT_7, -1.0, 1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CW, 1);

add_motor_raw(AP_MOTORS_MOT_8, 0.5, -1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CW, 5);

4) Get the code for your copter. In the Excel CAD program the code was generated and put into cell P2, the green cell.

Copy that cell (ctrl-C).

5) Paste (ctrl-V) the generated code for your copter into the V-Frame paragraph replacing the old add_motor_raw_line

of code. Delete or comment out the old add_motor_raw lines. In my case, the code now looks like this:

}else if( _frame_orientation == AP_MOTORS_V_FRAME ) {

// V frame set-up *****original numbers*****

// add_motor_raw(AP_MOTORS_MOT_1, 1.0, 0.34, AP_MOTORS_MATRIX_YAW_FACTOR_CW,7);

// add_motor_raw(AP_MOTORS_MOT_2,-1.0,-0.32, AP_MOTORS_MATRIX_YAW_FACTOR_CW,3);

// add_motor_raw(AP_MOTORS_MOT_3, 1.0,-0.32, AP_MOTORS_MATRIX_YAW_FACTOR_CCW,6);

// add_motor_raw(AP_MOTORS_MOT_4,-0.5,-1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CCW,4);// add_motor_raw(AP_MOTORS_MOT_5, 1.0, 1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CCW,8);

// add_motor_raw(AP_MOTORS_MOT_6,-1.0, 0.34, AP_MOTORS_MATRIX_YAW_FACTOR_CCW,2);

// add_motor_raw(AP_MOTORS_MOT_7,-1.0, 1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CW,1);

// add_motor_raw(AP_MOTORS_MOT_8, 0.5,-1.0, AP_MOTORS_MATRIX_YAW_FACTOR_CW,5);

// V frame set-up *****Frantz V 7/15/2013*****

// add_motor_raw(AP_MOTORS_MOT_5, 0.945, 1.000, 0.801, 5);

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// add_motor_raw(AP_MOTORS_MOT_7, -0.945, 1.000, -0.801, 7);

// add_motor_raw(AP_MOTORS_MOT_1, 0.757, 0.333, -0.801, 1);

// add_motor_raw(AP_MOTORS_MOT_6, -0.757, 0.333, 0.801, 6);

// add_motor_raw(AP_MOTORS_MOT_3, 0.570,-0.333, -0.629, 3);

// add_motor_raw(AP_MOTORS_MOT_2, -0.570,-0.333, 0.629, 2);

// add_motor_raw(AP_MOTORS_MOT_8, 0.383,-1.000, 0.629, 8);

// add_motor_raw(AP_MOTORS_MOT_4, -0.383,-1.000, -0.629, 4);

// X2 frame set-up *****Frantz V 9/22/2013*****

add_motor_raw(AP_MOTORS_MOT_5, 1.000, 1.000, 1.000, 1);

add_motor_raw(AP_MOTORS_MOT_7, -1.000, 1.000, -1.000, 2);

add_motor_raw(AP_MOTORS_MOT_1, 0.546, 0.504, -1.000, 3);

add_motor_raw(AP_MOTORS_MOT_6, -0.546, 0.504, 1.000, 4);

add_motor_raw(AP_MOTORS_MOT_3, 0.379,-0.504, 1.000, 5);

add_motor_raw(AP_MOTORS_MOT_2, -0.379,-0.504, -1.000, 6);

add_motor_raw(AP_MOTORS_MOT_8, 0.834,-1.000, -1.000, 7);

add_motor_raw(AP_MOTORS_MOT_4, -0.834,-1.000, 1.000, 8);

// Test Bench *****Frantz 8/6/2013*****

// add_motor_raw(AP_MOTORS_MOT_1, 0, 0, 0, 1);

// add_motor_raw(AP_MOTORS_MOT_2, 0, 0, 0, 2);

// add_motor_raw(AP_MOTORS_MOT_3, 0, 0, 0, 3);

// add_motor_raw(AP_MOTORS_MOT_4, 0, 0, 0, 4);

// add_motor_raw(AP_MOTORS_MOT_5, 0, 0, 0, 5);

// add_motor_raw(AP_MOTORS_MOT_6, 0, 0, 0, 6);

// add_motor_raw(AP_MOTORS_MOT_7, 0, 0, 0, 7);// add_motor_raw(AP_MOTORS_MOT_8, 0, 0, 0, 8);

}else {

Note that the // makes what follows it a comment that is ignored during the compile.

6) Save the file.

7) Download the firmware compiler (for details, see attached).

8) Verify the custom firmware code (for details, see attached).

9) Configure the compiler to your work-space (for details, see attached).

10) Compile and upload the custom firmware. One mouse click does it all! For details, see attached.

11) Set Mission Planner parameters. Load Mission Planner as normal and connect. Under Initial Setup > Mandatory

Hardware> Frame Type, select V.

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You are now ready to test the copter. Arm and make sure that all the props are rotating in the right direction. Don't g

nuts, there is more to do.

It's been a good day, so tomorrow we'll test and tune.

Attachments:

Custom Arduino Code Wiki Draft.docx,1.3 MB

Reply

Permalink Reply byForrest Frantz on September 26, 2013 at 10:56am

Installment VII: Test & Tune

The tune part will take weeks as you try different flight modes. But if the ship will hover without tuning, take a baselin

measurement to see how the copter is doing. Use the free Hover Analysis worksheet to set your baseline so you will

know how much the ship is improving during the tuning process. I'll post updates in the Vibration blog. See the

vibration wiki to see how to enable IMU/RAW, GPS, ATT, and CTUN, which are the records that Hover Analysis needs to

analyze vibration and stability.

For the X2 I saw this.

The left chart shows vibration at the APM. The short horizontal bars is where the system found the most stable 12 to 2

seconds of hover to analyze. That is why we have the ship hover for two minutes. Inexperienced pilots like myself nee

two minutes to get 12 seconds of stable hover! To fly, you need each random acceleration (vibration) to be less than .5

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gravities (G). The numbers in blue, purple, and gray above the chart show the metrics for each axis. And above that is

the average. The X2 has an average of 0.06. That is considered excellent. This is especially good since the craft is

lacking its normal payload of around +2kg in batteries and camera. Fully loaded, those numbers would drop

significantly. This metric is a 99.5 percentile number of the absolute values of the raw data ... a vibration spike that the

APM sees every 200 observations (necessary because the APM only samples accelerations).

Keep in mind that for the X2, the APM is bolted (no dampeners or isolators) directly into the same mast used to hold

four of the rotors. The other four rotors are zip tied to the same platform. The point being that if you:

o balance your props in x/y (on a standard balance)

o balance your props in z (the tip trace; the most intense source of vibration in z)

o use a stiff motor mast (decreases acceleration)

o reflect vibrations off of higher masses (where the motor masts meet the zip tie zone holding the central node).

o dampen by tying the mass directly to to APM ...

the ship won't need isolators for the extremely light APM. However, there are many ships that may need isolators.

And, the camera gimbal can almost always benefit from isolation/dampening.

Another number to watch is the signal to noise ratio on acceleration. Try to keep this above 2. The X2 is at 4. If I hadn

met the design goal of > 3 then more or larger zip ties could be added to the motor masts to tame vibration.

The right graph shows stability. As you dampen, stability won't change much (as long as the PIDs are tuned for the

weight). But if you isolate, stability will get worse. Consider that a law of physics. In stable mode at hover, yaw is not

controlled, so the statistics only looks at roll and pitch. The metric is in degrees from level and is the standard deviatio

from level. The X2 baseline (without tuning) had a stability of .22 and .17 respectively. That is good, but there is room

for improvement, so the X2 does need PID stability tuning.

So let's tune.

Some like to tune outdoors in flight using the variable knob on the radio. Some like to tune indoors. It's a personal

preference. I tune indoors and then validate outdoors. I have a slightly unique approach that uses Mission Planner to

track pitch and roll after a change in a parameter. I count the number of observations > .3 degrees per 50 and modify

the rules as I hone in on the best reading.

Now rerun the Hover Analysis to see if you made improvement.

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Much better! Even the Signal to noise increased to 4.3. Roll and pitch are now both in the excellent range.

Also in the Hover Analysis worksheet, in the orange area, is the THR_MID number that needs to be entered into the

Standard Params in Mission Planner. Enter that value into the Throttle Mid Pos. This will help keep the ship hovering a

about 50% throttle. I'll recheck that number for various payloads.

Congrats! You now have a flying machine that is better than most commercial ships.

Another good day. Tomorrow we validate. That is where we match up copter performance to requirements. Did we

make it? Tomorrow we find out.

Reply

Permalink Reply byForrest Frantz on September 27, 2013 at 3:28pm

Intallment VIII: Validation (videos) of the X2 Black Momba (motor loss test)

Does it do what was intended? Let's go through each requirement.

FOV: An 80 degree clean (no props) field of view for a camera sensor located at the ship geometric center (full sizecamera). A 120 FOV with the camera sensor located less than 7" forward of center (go pro) for pan 90 degree

downward to forward to 90 degrees upward.

Yes. Done via design. The front is wide open.

Total frame weight (bolts, masts, spars, platform, gussets, ties, etc.) < 400 grams.

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Close. 407 grams.

x/y/z accels < .1G

x/y/z accels all below .08G with average at .06G.

Not fail at 9G (crash) x 3.2 kg (approx max ship load)

TBD - not brave enough to test yet

Land safely with any 1-motor failure

Yes. Lands and takes off with the outside or inside rotor failure (see video of inside motor failure). The outside test

wasn't filmed. It happened by accident. I'd taken off, not paying attention, when my brother said, "Hey, think you

better land. You lost a motor." It was flying so stable that I didn't even notice (not good pilot technique; I have a lot to

learn).

https://www.youtube.com/watch?v=zPucFAqRNho&feature=youtube_gdata

Rotors with > 2 x 2.3 kg net-thrust (thrust after lifting themselves) or 575 net grams thrust per rotor.

Yes. This was accomplished during the selection process of testing motor efficiency. Net thrust for each rotor

was 792,779,766,778,802,779,772,785 grams for an average of 782 (in red italic below).

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APM located at center of x/y CG and positioned at the propeller z-plane.

Yes. Per design. There is a central hook centered under the APM that allows the pilot to pick up the craft from a single

dead center point and balance the ship by moving around the payload (batteries and camera).

Able to backpack.

Yes. Comes apart by:

- cutting 6 zip ties

- fold and velcro the two motor masts together

- attach to split-board (snow board) backpack using same method

- also bring zip-tie gun, zip ties, and zip-tie cutter (along with flying equipment and checklist)

- hike to location

- remove from backpack

- remove holding velcro and locate arm onto electronics platform lining up the plate holes

- apply six zip ties using zip-tie gun

- check out all electrical and mechanical connections

Able to assemble in field in < 12 minutes.

Yes. At a relaxed methodical pace it takes:

o 3 minutes to disassemble and velcro the masts together ready for transport.

o 10 minutes to remove from the pack, relocate/tie the masts in place, check all wires and mechanical connections.

Flight time with GoPro of > 30 minutes.

TBD. But did flight test using 12000 mAh batteries. The ship will carry a Go-Pro Black with 15000mAh batteries and sti

weigh less than the 50% of lift capability limit.

Looks promising. Flight duration on only 95% of 12000 mAh was over 30 minutes (no gopro but the gopro black only

weighs 10 grams per motor). With 15000 mAh the flight would be approximately 36 minutes (power consumptionwould increase from 22.1 to about 25 amps with the go-pro and extra battery capacity). So appears to have adequate

margin.

See the following video of the duration test. The log file is attached (was not tuned for for the payload).

https://www.youtube.com/watch?v=BcpgpoMZ5zE&feature=youtube_gdata

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Ability to support gimbal for high quality stills and videos.

TBD, but adequate mounting space on front. Can cut new electronics platform if needed.

140 Hz < hover frequency < 180 Hz.

Partial success & failure. Depending on payload, between 175Hz (lightest) and 212Hz (normal payload) Hz. But will beable to test 200 Hz flight by adjusting the payload and seeing the impact on stable hover.

That's it. Didn't take too long to build. Now I'll finish a few things up like tuning for different payloads; research

batteries and break the 30 minute barrier; and start working on the camera system. Should be fun.

Attachments:

2013-09-26 12-58 81.log,5.8 MB

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Permalink Reply byHugues on September 27, 2013 at 5:50pm

Wow! Excellent post. You should move it from unassigned category to arducopter group category because everybody

like me missed it.

How would you plan to fix your gimbal on this frame?

Why not installing the motors upside down and reverse the props, so that the props do not blow on the beams? Thiswould force a landing gear design allowing this.

What would be nice , but probably a dream, would be to integrate the battery within the hollowed carbon tubes...

The way you stack ESCs is not ideal for heat dispersion because you block convection and radiance. But it depends if

they heat up much or not after 30min.

APM case is not protected from the sun: heat and light. The integrated barometer is sensitive to light and heat. The

translucid case and foam on top of the baro is not enough. Either a black dome on top, either paint the case black. I

experienced, like others issue with APM in full sun.

going to sleep now, it is 2am...will comment further with fresh eyes...

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Permalink Reply byForrest Frantz on September 27, 2013 at 7:42pm

Great puts. Didn't know about the sun light. that might explain why my V had alt-hold issues. would sit there for a

while and then just slowly fall out of the sky.

that battery idea is such a great idea. wish i knew how to make them. i could save another 150 grams probably.

with the batteries on the bottom, the camera is going out front at frame level. when i do this, one or more batteries w

move to the back. this will give the camera the ability to point straight down, out, or up. i live by a volcano (mostly

inactive) and have this image of the camera pointed straight up as it takes off straight up through the trees and then as

it peeks out even with the trees (around 40 meters), it rotates flat to the mountain, flies over the waterfall and then

pans down to the abyss. that is the image that has driven me on this project.

actually had the motors reversed (lawn mower style) on the V for that reason. but then did some tests and found that

to my great surprise that it had little impact on vibration and only a small impact on lift. really strange. doesn't make

sense. the round tubes help, but ???

so would putting the 18-amp esc's on end with the hot side up help? i only run at less than 3 amps which is why they

haven't been a problem, but i need to be setting a good example, which i'm not.

i'll find a cheese container or something and put it over the APM. should i paint it silver, white, or black?

Round tubes are back.

The goal of this build has various missions:

1) show how easy it is to build a ship on par with commercial ships.

2) stay aloft for over 30 minutes carrying a full-size camera.

3) use low Kv motors and low voltage to create an efficient ship but stable camera platform (adesign that is usually contrary to the objective).

4) fly at slightly less than 200 Hz but also be able to fly at 200 Hz (the evil frequency) to testthe impact of doing that when vibrations are only managed by frame stiffness and low mass.

5) test light methods to mitigate the more fragile cloth/woven carbon tubes.

6) test APM code flexibility on flying a new octa motor layout.

After a successful test using braided carbon fiber tubes that are basically indestructible,strong, stiff, light, and provide a surface that is easy to bond, this discussion will focus onusing cloth or woven carbon fiber tubes. Relative to braided tubes, woven tubes have asmooth surface (not as easy to bond), have a lower resin content, and layered fibers. Braidedtubes use fibers that are braided from the inside layer to the outside layer. Woven tubesstack and bond either cloth or tape layers placed in multiple directions to derive engineeredstiffness and light weight. But unlike pultruded (where most all fibers in one direction), there

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are axial fibers to keep cracks from propagating. Why not just stay with braided? Wovencarbon tubes are more available, come in more sizes, and are lighter for their stiffness.

This discussion will go from design through flight tests.

Replies to This Discussion

PermalinkReply byHugueson September 28, 2013 at 8:01am

Do not know how to change category, except copy paste on a new post in the rightcategory and then delete this one.

For APM I would paint it a IR reflective paint (silver or white probably better than black)you could paint the APM case itself like most people do.

I personally use this that comes in different

colors:http://www.uavshop.co.uk/catalog/product_info.php?cPath=65&prod...

I would not put the ESC too far from the battery otherwise you are good to addcapacitors on the battery input of each ESC.

I am thinking more of a kind of open book with pages, representing the ESCs, evenlyspread on 180 degrees. In such a way each ESC receives enough fresh airflow and thwhole remains compact.

Thanks Hugues - I really didn't understand the ESCs. Thought the hot part was thecapacitor and had those into the wind.

My EE brother explained that it's the six identical looking FETs at the edges of the ESCcircuit board that need cooling. Those should be faced into the wind and protectedfrom hot sun. They are susceptible to frying if they get wet. What he recommendedwas to remove the shrink wrap around the FETs. Put a dab of silicone on each one.Then bond on aluminium foil or a piece of a soda can on top of of the FET/silicone for aheat sink. Sand off any dark print for a UV reflective surface first.

I'm doing to go from 20 amp ESCs to 10 amp, saving 110 grams. I'll do the the heatsink then.

Very inspiring post! So much done already and the results are looking good.

Would pulling COG forward by slightly opening the masts angle, shortening the taillength and pushing the center plate forward compromise any of your prerequisites?

And wouldn't these changes result in:

1) Better pitch stability control?

2) Smaller center plate?

3) Larger unobstructed surface (on both faces) of center plate?

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4) Less spacers for fixing electronic components?

5) No need for a secondary plate for gimbal support?

I would love to try some octa design alternatives. I believe the excel CAD tool usedhere was made by you. Is there any chance I can use it?

Not at all. The design tool does all of the calcs.

make sure that CG is in the center of the motors unless you want one set of motorsworking at a different rpm than the other set (it will fly just fine either way but you mightsee a decrease in efficiency). moving the bulk of a light electronics platform plateforward does little to upset CG. putting a camera way out there can be easily offset bybattery placement. just use the really stiff sandwich panel to minimize oscillation. theCG isn't where the bars cross then the aft is narrower than the front. the CG is forwarda bit (the worksheet makes the calc).

pitch stability is controlled by tuning the PIDs. for example the X2 has a roll P of .31

and a pitch P of .22 for certain payloads.

the center plate can be smaller. i only use a large one so i can separate the antennaseven using light material, area weight does add up. that plate weighs 68 grams (woulbe happier with about 40).

the only reason to raise the GPS is to get it a bit higher relative to the motor masts forlow horizon sats (probably not necessary but didn't know for sure). the GPS is alsomore protected by the motor masts when it's lower so made a trade (probably anunnecessary one as you pointed out).

the only reason to raise the APM was to get it exactly centered (don't know how

important that is). maybe i'll experiment with this and move it forward so it can go flatonto the platform.

the 1/4" sandwich panel is 23x stiffer than 8-ply carbon plate and weighs 1/4th asmuch. the only thing you need to consider with that material is that the skins are oneply. so sometimes you need to reinforce by bonding on a layer of fiberglass or wood ifyou are transferring loads to a different direction. the APM forward U has suchreinforcement.

attached is the Excel CAD. unfortunately, there is no real standard between the tabs(as in they should all work the same but don't). so it's a bit crude. some of the FOVs

don't work. you can tell which tabs got the most use by how sophisticated they are. soif you get into a tab (design type) and want some work done, let me know and i'll fix it.if you make improvement to the equations or macros please share.

I also have worksheets for quads and hexas.

small thing: in the Excel CAD file, for the tab "H", there seem to be a hickup in cell O3.

then there are a couple of "REF#" and "VALUE#" as well in k60-m63.

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or did I make a wrong input somewhere?

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PermalinkReply byForrest Frantzon December 12, 2013 at 5:04am

Re: Custom Octa CAD [tab H]

It's never you. It's me trying to do too much :-)

Cell O3 - Change #REF! to J35 (this is what you paste into the Arducopter code)

Cells K60 - M63 - Ignore all of J48 through M63 (it is old code replaced by J7 - M35)

Thanks for reporting that.

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PermalinkReply byJean-Philippeon December 13, 2013 at 7:18am

thank you Forrest for the correction.

This helps me. I am a little bit scared to modify the arducopter code, but willing to giveit a good try :)

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PermalinkReply byJean-Philippeon December 17, 2013 at 3:52pm

Forrest, It took me a little while to figure out that my regional settings in Excel were alsplaying a big twist on me with the format for number with decimals the "." and the ","story. All good now :)

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Permalink

Reply byrjc_quadcopteron September 28, 2013 at 8:05amHi Forrest,

Very inspiring and educational! Thanks.. I am taking some notes from your posts..

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PermalinkReply byForrest Frantzon September 28, 2013 at 10:53am

Installment IX: Maintenance

A. Props- Every so often lift off, hover for two minutes, land, turn off power to the APM

(necessary to end the log), then go fly for fun. When you get back, run the HoverAnalysis excel worksheet to see if you are picking up more vibrations. The culprit ismost likely planar prop adjustments that are needed unless you are missing a fewchunks, so check your prop tip trace. After a crash, also suspect a bent shaft if propbalancing doesn't do the trick.

B. Pre-Flight, Flight, Post-Flight- My older brother, a retired NW Airlines pilot, gotme into using a checklist and verbally saying out loud each item as I go through it. Ouloud is critical or you will mindlessly skim. Also physically check of each box. Your listwill vary depending on the type of electronics you have. See attached if you want touse it to customize for your ship. What I like about this version is:

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o it is tailored to my ship. when a camera or FPV is added, then those steps will beadded.

o i print off one per battery set prior to every flight; each sheet is good for up to fourflights on one battery set

o it reminds me how the radio is set up for each mode (my brother also added tape witwords to his radio)

o it's broken down by where i do each task (man-cave, launch site)

C. Batteries & Flight Log- My brother also got me in the habit of tracking one of yourmost important resources, your batteries along with other flight data (how hard did youcrash, etc.). This also can make it easier to identify which APM log was for which flighand what were the payload and weather conditions during that flight.

o it keeps a track of estimated max flight time and amp usage rate for that payload.

o it tracks battery condition so you know if your battery is getting weak.

D. Bearings- Replacing bearings isn't that hard. Just don't do what I did and pop offthe axle clip and let if fly where i never found it. There are some blogs on bearing thatare really good that talk about sites for identifying which bearing your motor takes andhow to buy them. Also, sometimes a stator might break loose from the shaft. That toois easily fixed with Loctite as long as you are careful not to get the glue on thebearings. And some motors are so cheap that it's faster and cheaper just to buy newones and have a spare laying around.

E. Spares

- Several CCW and CW props

- An ESC

- A motor

- Other parts particular to your ship (e.g., zip ties).

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Attachments:

Flight Check List.docx,101 KB

Log Book.xlsx,37 KB

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PermalinkReply byHugueson September 30, 2013 at 11:33am

This is great. I was thinking about logging my flights for tracing the lifecycle ofcomponents and to log how many hours equivalent I flew a drone. You went faster thamy thoughts.

I will reuse your templates. Thx.

Did you already change a bearing on a motor ? Could you post a video doing it ? I'dlike to learn that.

Some thoughts about spare parts and check lists:

-I always had one ESC and one motor as spare parts. Result : not sufficient. You needtwo for most craft configurations : indeed when it tips over, by default it will hold on twomotors. Last summer in France I got grounded because it happened to me and I hadonly one spare ESC instead of two...

-Props : take also multiple sizes/pitches. I always decide at the last moment what willbe my final payload configuration. So I can change my thrust profile at the last minuteby changing my props.

-Extra batteries (charged) for your camera(s) and for the drone AND the radio (we

forget that one often because their battery last very long..)

-Something very dangerous to add in the checklist : are there dogs around ? If yes DONOT fly. These doggies love (mine does) to run after what they think is a big insect.