Stumpy
An autonomous bipedal robot
Michael Cowling | Andrew Jeffs | Nathan Kaesler
Supervisors: Dr Frank Wornle | Mr George OsborneSchool of
Mechanical EngineeringMechatronics Honours Project 2005
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History of bipedal walking robots1968~1969: first functional
robot: WL-3Current: fully functioning humanoids such as Honda ASIMO
and Sony QRIOApplicationsProsthetics for the
disabledEntertainmentHuman assistance
BackgroundMechanical Engineering*Sony 2005Honda 2005Bipedal
walking robotswww.humanoid.rise.waseda.ac.jpMultifunctional
Above-knee Prosthesiswww.humanoid.rise.waseda.ac.jp
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MotivationUniversity of Adelaide designed pneumatic muscles
Stimulate robotics research at the UniversityMechanical
Engineering*
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Seminar OutlineProject aimsControl techniquesTraditional method:
biomechanicalContemporary method: gait synthesisPassive dynamic
design conceptDesign processPassive biped for downhill
walkingPneumatic muscle actuated bipedResults and future
directions
Mechanical Engineering*
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AimsDesign and build a unactuated bipedExtend design to
incorporate muscle actuationMake self-containedExtension goal:
incorporate standing still, stopping and startingMechanical
Engineering*
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Design MethodologiesTwo main design methodsBiomechanical
controlTraditional control methodRobust and versatileRobotic
looking gaitDifficult and expensive to implementUnnecessarily
complexInefficient and heavyControl based on gait synthesisAsimo X2
at Robodex 2003http://www.plyojump.com/asimo.htmlMechanical
Engineering*
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Control by Gait SynthesisSimulate natural kinematics of
walkingBegins with essentials of walkingActuate only when
requiredRelatively new approachMcGeer 1990, Wisse 2004Inherent
sequential designSuited to muscle actuationSimple control
requiredVery efficient
Collins et al 2005Mechanical Engineering*
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Control by Gait SynthesisPassive dynamic conceptGravitational
power onlyPerfect starting pointNatural looking gaitSimple and
lightLeads to human-like behaviourOnly dynamically stable
Collins et al 2005Collins et al 2005Mechanical Engineering*
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Preliminary DesignGait synthesis approach chosenSimplifications
to human physiologyFewer degrees of freedomMinimal
actuatorsSimplest walker conceptNatural starting pointPrototypes
for feasibilityMancano promisingLegoman unsuccessful
Simplest
Walkerhttp://mms.tudelft.nl/dbl/research/bipedMancanoLegomanMechanical
Engineering*
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Design of StumpyExtremely difficult taskDiscrete events and
varying configurationNon-linear and naturally unstable
dynamicsComplex mathematical modelEmpirical results requiredDesign
based on McGeers kneed walking modelUnactuated kneed bipedMade
goals achievable
McGeer 1990Mechanical Engineering*
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Mechanical DesignSimple mechanical layoutFour legs in
pairsPinned knee jointsCurved feetConsideration for tuning and
actuationLimb lengthsWeight distributionMuscle mountingFoot
position and radius
Mechanical Engineering*
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Final Design
Mechanical Engineering*
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Testing and ResultsMany variablesLimb lengthsFoot radiusMass
distributionRamp angleStarting conditionsSuccess!
Mechanical Engineering*
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Testing and ResultsPoor repeatabilityKnee bounce main failure
mechanismKnee damping ineffectiveLatch requiredVery promising for
next design stage
Mechanical Engineering*
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Biped ActuationPassive biped has limited functionalityOnly walks
downhillCannot start, stop or stand stillActuation can overcome
theseModify passive bipedAdd actuationAdd associated power and
control
Mechanical Engineering*
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Muscle ActuationPneumatic muscle operationMains air or bottled
CO2 supply (~2 bar)Power required for switchingPreserves passive
dynamic actionOther benefitsSimple constructionLight and
powerfulLow costEfficient
Mechanical Engineering*
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MechanicsVarious muscle configurations possibleActuate knees
onlyActuate hips, and use knee latchesActuate all joints, with
either 1 or 2 muscles on eachFive muscles usedAntagonistic hip
arrangementOnly two actuators requiredSimple lever arm
attachmentMuscle-spring system for kneesMechanical Engineering*
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Electronics and ControlMotorola 9S12C32 microcontroller
on-boardH-Bridge muscle switchingOn/off muscle sequencingReal-time
tuning via PCOn-board user controlsFoot switch cycle
initialisationLi-ion batteries for power and
electronicsMicroH-BridgeMechanical Engineering*
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Final design
Mechanical Engineering*
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ResultsStumpy walks successfully with some assistance
Mechanical Engineering*
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AchievementsStumpy walked passivelyActuated walking
successfulWill improve with fine tuningSelf-contained, but with
mobile gas supplyMechanical Engineering*
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Future DirectionsStanding still, starting and
stoppingTurningIncorporating upper bodyMore degrees of freedomTwo
legsActive ankles
Mechanical Engineering*
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ConclusionGait synthesis instead of biomechanical controlTwo
prototypes builtPassive biped Stumpy based on existing designWalked
successfullyMuscle actuation added to StumpyPowered biped walked
with some assistance
Mechanical Engineering*
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AcknowledgementsSupervisorsDr Frank Wornle and Mr George
OsborneMechanical engineering workshop staffElectronics and
instrumentation staffMechanical Engineering*
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QuestionsMechanical Engineering*
gggbased on essentials of human walkingbased on essentials of
human walking
