Line Followers: Basic to Proportional - ev3lessons.comev3lessons.com/en/ProgrammingLessons/advanced/LineFollower.pdf · Smooth Line Follower + +--Simple Line Follower + +--Proportional

ADVANCEDEV3PROGRAMMINGLESSON

LineFollowers:BasictoProportionalBySanjayandArvindSeshan

ì Evaluateandcomparedifferentlinefollowers

ì Learntousetheconceptof“proportional”tocreateaproportionallinefollower

ì Prerequisites:BasicLineFollower,ColorLineFollower,ColorSensorCalibration,ProportionalControl,MathBlocks,DataWires

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LessonObjectives

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WhichProgramWorksBestforWhichSituation?

SmoothLineFollower• Almostthesameassimple• Turnsarelesssharp• Hastroubleonsharpcurves• Good forrookieteamsà needtoknow

loopsandswitches

SimpleLineFollower• Mostbasiclinefollower• Wigglesalotduetosharpturns• Good forrookieteamsà needto

knowloopsandswitches

ProportionalFollower• Usesthe“P”inPID• Makesproportional turns• Workswellonbothstraightandcurved

lines• Good forintermediatetoadvanced

teamsà needtoknowmathblocksanddatawires

3-StageFollower• Bestforstraightlines• Droidsdonot recommendthis.

Justlearntheproportional linefollower.

• Needtoknownestedswitches

Watchthevideosonthenext2slidestoseeallfour.

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CurvedLine:WatchVideos

SmoothLineFollowerSimpleLineFollower

Proportional Follower3-StageFollower

StraightLine:WatchVideos

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SmoothLineFollowerSimpleLineFollower

Proportional Follower3-StageFollower

ì Challenge1:Canyouwriteasimplelinefollower?Hint:ReviewBeginner:BasicLineFollowerlesson

ì Challenge2:Canyouwriteasmootherlinefollower?Hint:Changehowsharptheturnsareinasimplelinefollower.

ì Challenge3:Canyouwriteathree-stagelinefollowerwheretherobotmovesdifferent3differentways(left,rightorstraight)basedonthereadingfromthecolorsensor?

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3LineFollowerChallenges

ì CALIBRATE:ì TheprogramsusetheEV3ColorSensorinLightSensormodeì Youwillhavetocalibrateyoursensors.ì PleaserefertoIntermediate:ColorSensorCalibrationLesson

ì PORTS:ì TheColorSensorisconnectedtoPort3.ì Pleasechangethisforyourrobot.

ì WHICHSIDEOFTHELINE:ì Pleasetakenoteofwhichsideofthelinethecodeiswrittenfor

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ANoteAboutOurSolutions

Solution1:SimpleLineFollower

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Solution2:SmoothLineFollower

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Solution3:Three-StageLineFollower

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Challenge4:Canyouwriteaproportionallinefollowerthatchangestheangleoftheturndependingonhowfarawayfromthelinetherobotis?

Pseudocode:

1. ResettheRotationsensor(Onlyrequiredforlinefollowingforatotaldistance)

2. Computetheerror=Distancefromline=(Lightsensorreading– TargetReading)

3. Scaletheerrortodetermineacorrectionamount.Adjustyourscalingfactortomakeyourobotfollowthelinemoresmoothly.

4. UsetheCorrectionvalue(computerinStep3)toadjusttherobot’sturntowardstheline.

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Challenge4:ProportionalLineFollower

Solution:ProportionalLineFollower

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ì Youwillgetbetterresults

ì ….ifyourcolorsensorsareclosertotheground

ì ….remembertocalibrate

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Tips

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DiscussionGuide

SmoothLineFollower++--

SimpleLineFollower++--

ProportionalFollower++--

Three-StageLineFollower++--

Fillintheabovewithpositivesandnegativesofeachtechnique.Consider ifthelinefollowerisbestforcurvedorstraightlines.Consider iftherobotwillwigglealot.

ì ThistutorialwascreatedbySanjaySeshan andArvindSeshan

ì Morelessonsatwww.ev3lessons.com

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Credits

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.