RollingPlatformDriverChallenge
Description
Inthisactivity,studentswillbuild abasicrollingplatform robot thatwillserve as achassisforadditionalactivities listed inthis module.This activity’s primary missionistoconstructa robotthat will move forward andbackward andturn left and right. The chassis will illustrate keyprinciples of traction,torqueandbattery power.
Students willconduct this activity ina teamenvironment, develop their capacity for followinginstructions, make adjustmentsto improve robot performance andbe exposedto concepts andterminology they canuse toassesstheir design.
Novice studentsmayconsider constructing therolling platform using instructions andinformation available directly from therobotmanufacturer’swebsite. Use thefollowingkeywordsalongwiththe platform nameto searchthe internet for examples:clawbot, rolling bot or tank.
Forintermediatestudents,consultexisting platforms andexamplesavailableonlinefirst. Next,augment thesebasicdesigns to constructa rollingplatform that bestsuits yourclass’s needs.
LessonOutcomes
Students willbeable to:
•Construct and operatea robotthat isableto make basic manoeuvres
•Follow instructions to completeacomplexassembly task
•Understandand apply gearratiostotheirdesign
•Apply designthinking to improve theirrolling platform’sperformance
•Demonstrate constructiveteamwork skills
Assumptions
Studentswillhave:
•Someknowledge of basic construction techniques
•Formed teams and partnerships withinthe classroom
•Access toroboticsplatforms and necessaryequipment
•Someknowledge ofgear ratios,robots and design
•Someexperiencewithbasic mathematics, friction, torque andelementaryforces
•Some experiencewithrelevanttoyssuchasLEGO,bicycles,wagonsand fictional robotsfrom movies (e.g.,R2D2, BB8)
Thisworkis licensedunder aCreativeCommonsAttribution-NonCommercial-ShareAlike4.0InternationalLicenseunlessotherwiseindicated.
KeyTerminology
Centerofgravity:afocalpointwhereanobjectisstandingatitsdesignmaximumwithoutfallingdown.
Chassis:aphysicalstructurethatconnectsandholdsthevariouscomponentstogethertoformthebasicrobot.Inmostcasesitcanbetheouter shellortheinternalskeleton structure.
DesignThinking:isanapproachtosolutions-findingthatconsidersthedesiredend-resultorexperience.ADesignThinkingapproachisoften iterative, startingwiththedefinitionofaproblem,empatheticallyconsideringtheexperienceorimpactofthatproblemfrommultiple
perspectives,consideringmultipleapproachestopotential solutions,thennarrowingdownthesolutionthroughprototypingorexperimentation.Thechosenapproachtothesolutionisthenselectedandimplemented.
Friction:heatcausedbyopposingforcesactingonasurface.ORaforcethatresistsmotionbetweentwosurfacesslidingagainst eachother;strengthoftheforceisdeterminedby theirtextures.
Gearratio:thescienceofmechanicaladvantageusinggears.
Scrub:thetransverse(side-to-side)frictiononawheelinaskid-steerdrivetrain.
Skidsteering:turningavehiclebydrivingtheleftsidedrivewheelsatadifferentratethantherightdrivewheels,similartoatankor bulldozer.
Torque:alsoknownasmoment. Theforceofamovingobjectconnectedtoasinglepoint.
ORthemeasurementofforcecausingrotation.
Traction: theabilitytogripasurface.
EstimatedTime
3–4hours or more (platform dependent)
RecommendedNumberofStudents
Twotofivestudentsperrobot,perteam(ideal:threestudents)Twotofiveteams
Facilities
Robot testing area: alarge table,approximately120cm × 240cm (4ft.× 8ft.)Any classroom withtables
Storagespace
Tools
Toolsare platform-specific, depending on the robotics platform selectedStopwatch
Materials
Storagebins
Robotkits(e.g.,VEXEDR,VEXIQ, LEGOMindstorms)
Resources
“Simbotics” is alsoknownas Team1114,former WorldChampions of FIRSTRobotics andoneofthemostfamous high schoolrobotics teamsinCanada.They produce some excellenttrainingmaterials thatthey sharewith theroboticscommunity,includingthis presentation onrobot drivetrains. It is,perhaps, morein-depth thanneededforpresentationtothe class, but it
provides excellentbackground information ondrivetrainsfor the teacher or advanced studentsintheclass:
VEX Robotics has curriculum onrobot design. This sectionondrivetrain designis relevant tothis activity,particularly thesections on traction, turning andgears. Much of itis writtenat ahighschoollevel.
Asimportant asit is forrobots to beable to turn, it isalsoimportant to get themtogostraight.This 15-minutevideodiscusses how toget a LEGOrobot to travel in astraight line. Italsodemonstrates good scientific practice inmeasuringandrecording performance.
Demonstration
Ideally the teacher will haveaccess toa workingrobotdrivetrain todemonstrate howitworks.Particular emphasisshouldbe placedon the importanceofkeeping the centre of massoverthedrive wheels, and dealing with“scrub” or“skid,”the sidewaysforce acting onthe front andrear wheelswhen a“tankstyle” or “skid steer” drivetrain changesdirection (seeFigure1).It isalsoimportant to referencethe relationshipbetween drivewheel diameter, gearratioand motortorque. Inthe event that ademonstration robot isnot available, someofthevideos below willhelp cover the relevant topics.
Figure1—Three simpleVEX-based“rollingchassis” using “skid”steering.Theleft-hand robotusesomniwheels on thefront axle to help reduce“scrub”and maketurningeasier.
Thefollowingvideoswillprovide anunderstanding of gearratios. Itis recommended thatteachers preview the followingvideosbeforeshowing them totheirstudents in class. Note thatthesearethe samevideos linked as aresource inActivity 3,“EssentialPrinciples ofRobotics.”Students who havecompletedthat activitymay already be familiarwiththis content.
GearRatios-Part1
GearRatios-Part2
GearRatios-Part3
Thefollowing videos will provide anunderstanding of speed vs.strength(torque):
UnderstandingGears:SpeedVs.Torque:atwo-minutedemoofsimple gearratios
LEGOTechnic-Torque,Speed,Gearing
Also, discuss centre of gravity as aconcept and howit affects theconstruction andoperationofyour rollingplatform.
Procedure
1.Students build their rollingplatform. Theymay followthesereference materials tobuildthebasic rollingplatforms:
VEXIQ(animatedinstructions)
VEXIQ(buildinstructionPDF)
VEXEDR(buildinstructionPDF)
LEGOMindstorms/EV3(buildinstructionPDF)
2.Afterconstructingtherollingplatform,students should test theirrollingplatform tosee if itperforms accordingto plan.
3.Introducethefollowingactivity as acompetitive challengeto getstudentsaccustomedtothearenaof competitive robotics challenges. Be sure tohavea stopwatchonhandto keep time.
TestingYourRobotChallenge—NavigatetheMaze
Theobject ofthis challenge is to remotely control therolling platform to travel from one sideofthemazeto thenext. This activity is scoredby a stopwatch.
Therollingplatform starts in contact with the wallononeside of the maze, then crosses to theother sideto touchthedestination wall, at which point thetimeris stopped. The rollingplatformcannot simply climb over the wall(s) to gettothe other side.The team with theshortest timewins the challenge.
Figure 2 showsonepossible“maze”configuration.Slalom courses and “head-to-head” racingonparalleltracksalso make for exciting activities.
Figure2—Onepossiblemazelayout
ExtensionActivities
Extensionactivities maybe found at thefollowing website underClassroom Challengesat thebottomof the page:
Jr.Robotics:aplaceforteachers,studentsandparents:
Assessment
The evaluation of this lessonisbasedon thelearning outcomes outlined above.
Prior toteachersusingthe evaluation griditis recommended that studentsperform someformofpeer-assessment andself-assessment.
OutcomeToBeAssessed / 6 / 5 / 4 / 3 / 2 / 1 / 0Outcome1 / RobotConstruction
1.1 / Construction of robot to specifications.
1.2 / Understandsandappliesgear ratios tothedesign.
1.3 / Follows instructions tocompleteacomplexassemblytask.
Outcome2 / PerformtheTechnicalChallenge
2.1 / Robotsuccessfully navigates themaze(s).
2.2 / Appliesdesignthinkingto improvetheir rollingplatform’sperformance.
Outcome3 / Teamwork
3.1 / Able to resolve challengeswhen encountered.
3.2 / Equitable division of work.
Outcome4 / UnderstandingKeyTerminology
4.1 / Demonstratestheuseof KeyTerminology.
4.2 / Appliesterminology appropriately.
TotalPoints:
6 / Completedsuccessfully atthe exceptional level / Exemplary5 / Completedsuccessfully athigher than theexpected level / Accomplished
4 / Completedsuccessfully to theexpectedlevel / Emerging
3 / Attemptedsuccessfullyat the minimumlevel / Developing
2 / Attempted- Unsuccessful- ClosetoSuccessful / Beginning
1 / Attempted-Unsuccessful / Basic
0 / NotAttempted / N/A
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