Lecture 02: Locomotion
- 1. Introduction to RoboticsLocomotionCSCI 4830/7000January 11, 2010NikolausCorrell
- 2. What is locomotion?Latin: moving from place to placeCrawlingSlidingRunningJumpingWalkingRolling
- 3. Other forms of locomotionSwimmingGlidingFlyingPropulsion
- 4. Locomotion relationshipsSwimming to walkingWalking to rollingGliding to flyingRunning to jumpingA.J. Ijspeert, A. Crespi, D. Ryczko, and J.M. Cabelguen. From swimming to walking with a salamander robot driven by a spinal cord model. Science, 9 March 2007, Vol. 315. no. 5817, pp. 1416 - 1420, 2007.
- 5. Nature vs. TechnologyRobots become more and more capable of imitating natural locomotion schemesNature did not evolve rotating shafts / rotational jointsHinge jointBall and socket joint
- 6. Walking vs. rollingIf the terrain allows, rolling is more efficientWalking requires moreStructural complexityJointsControl
- 7. Characterization of locomotionStabilityNumber of contact pointsCenter of gravityStatic/Dynamic StabilizationInclination of terrainContactPoint vs. AreaFriction vs. grasp3-Point rule3 legs : static stability6 legs : static walking
- 8. Walking2-DOF4-DOF6-DOFHow many DOF are needed?
- 9. GaitSequence of event sequenceEvent: leg up or downPossible number of gaits N=(2k-1)!Most efficient gait is a function of speed!
- 10. Horse Gait (Gallop)167 different gaits observed in a horse!
- 11. Industry2-legged locomotionpopular because suited to human environmenthardest to controlCommercial prototypes4-legged locomotionNot statically stableCommercial prototypes6-legged locomotionStatically stableForestryhttp://www.youtube.com/watch?v=FAcgSi6pzv4http://www.youtube.com/watch?v=CD2V8GFqk_Y
- 12. Wheeled locomotionMost appropriate for most applicationsStable with at least 3 wheelsSteered wheels make control more complex pretty quicklyStable zone
- 13. Wheel suspensionSuspension consists of a spring and damperThe damper absorbs shockThe spring counteracts the shockResult: wheel remains on groundBetter tractionBetter control
- 14. Omni-Directional DriveSwedish WheelRotation around wheel axleRotation around the rollersRotation around contact pointUranus, CMU
- 16. Dynamic StabilityThe system has to move in order not to fall overActive balanceInertia is used to overcome unstable statesExamples areRunningGetting upInverted Pendulum
- 18. Brushed DC MotorDirectly driven by DC currentSelf-commutatingSpeed regulated by voltageNeeds gear-box to generate useful speed/torque
- 19. Stepper MotorRequires dedicated circuitry to generate activation sequenceSpeed of sequence controls motor speedMotor stops at precise increments
- 20. Brushless DC MotorCommutation done electronicallyRequires speed controllerMore efficient then brushed DC Motor
- 21. EncodersRequired to estimate axis positionOptical encodersDifferentialQuadratureAbsoluteHall-Effect
- 22. ServosServo =motor + encoder + gearbox + controllerLow-End:Pulse-Width Modulation (PWM):rate regulates positionHigh-End:Digital control allows setting and querying position, speed and torque
- 23. Linear ActuatorsRotation-basedHydraulic / PneumaticSolenoidPiezo-ElectricShape-Memory Alloy (SMA) wires
- 24. DesignLets design robots thatCrawlSlideGallopJumpWalkRollCrawlingSlidingRunningJumpingWalkingRolling
- 25. CrawlingMechanics of Soft Materials Laboratoryhttp://ase.tufts.edu/msml/researchInchBot.asp
- 27. RunningScout II, McGill Universityhttp://www.youtube.com/watch?v=SRIU7PtyGOw
- 28. JumpingLaboratory of Intelligent Systems, EPFLhttp://lis.epfl.ch/?content=research/projects/SelfDeployingMicroglider/
- 30. HomeworkChapter 3Required for next week’s exerciseHintsread the questions firstSkip: 3.2.3.4-5Skim: 3.2.4-3.3.3Understand what Maneuverability (Mobility and Steerability is) conceptionallyGoal: calculate the speed of your robot’s motors so that it can follow a desired trajectory
- 31. Next exerciseLocomotion (1 week)Play with different locomotion concepts in WebotsUnderstand various gaitsCome up with a “stand-up-gait” for the Soccer robot