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Legged Robotics & BigDogMarc Raibert: Boston Dynamics
Andy SchmidtUniversity of North Carolina at Charlotte
April 16, 2008
Boston Dynamics - BigDog
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Raibert’s Legged Robotics Paper
Why Legged Machines?1. Traverse difficult train
I Wheels excel on prepared surfacesI Legs allow travel to more remote areas
2. Active suspension of body from feetI Body travels “smoothly” despite variations in terrainI Legged system can choose among best footholdsI Do not need constant contact with surface
Boston Dynamics - BigDog
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Raibert’s Legged Robotics Paper
Pitfalls:I Joint movementI BalanceI Current and future foothold calculations
Boston Dynamics - BigDog
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Legged Robotics - History
I 1870s - Simple walking machinesI 1960s - Human Control (I.E. GE Legged Truck)I 1970s - Computer Control (Ohio State University - 1977)I Linkages to provide appropriate stepping motionsI Limitation: No Control - Best footholds
Static Balance: Some feet on ground to guarantee support
Boston Dynamics - BigDog
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General Electrical Legged Truck
Boston Dynamics - BigDog
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Legged Robotics - Active Balance
Active Balance: Legged systems operating while consideringvelocities and kinetic energies of the masses
I Challenges:I Energy stored in each mass and springI Geometric structure and configurationI Velocity
I Running with respect to Active BalancingI Tip and accelerate (short) then tip in opposite directionI An effective base (balance) is maintained over timeI Result: Improved mobility
Boston Dynamics - BigDog
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Legged Robotics - Running Machines
I Running Cycle:Stance Leg supports weight of body
Flight Center of mass moves ballistically allowingunloaded leg to move freely
I Running Control:Hopping Delivered vertical thrust with the leg during
each support period to sustain oscillation andregulate amplitude
Forward Speed Calculate the next foot position (angle)which plays into the speed
Posture Stabilize pitch angle of body to keep it upright
Boston Dynamics - BigDog
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Marc Raibert’s One Legged Robot
Boston Dynamics - BigDog
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Legged Robotics - From One to Four Legs
I Bi-beds run with alternating support and flightI One leg is placed on the ground at a timeI Virtual Leg: Group of legs with simultaneous supportI One virtual leg provides support / flight at a timeI Trotting quadruped = biped = one-legged machine
Boston Dynamics - BigDog
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Boston Dynamics
I Started by Marc Raibert (MIT) in 1992I Focus on Human Simulation and Robotics
Sony Entertainment RobotsArmy Institute for Creative Technologies
Marines Marine Expeditionary Rifle SquadI Robotics:
BigDog Quadruped RobotLittleDog Legged Learning Robot
RHex Remote Controlled Terrain RobotRiSE Climbing (as in vertical!) Robot
Boston Dynamics - BigDog
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Boston Dynamics - DI Guy
Boston Dynamics - BigDog
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Boston Dynamics - BigDog
Requirements:I Capable of runningI Jumping over objects 1 meter tall or 2 meters wideI Traverse a variety of terrainI Operate for two hours without refueling
Boston Dynamics - BigDog
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Boston Dynamics - BigDog
BigDog Stats:Size 1 meter long × 0.7 meters tall
Weight 75 KgPower One Cylinder Gas engine and battery
Hydraulic Actuators 3 joints repositioned up to 500/secSpeed 4 mphClimbs 35–45◦
Load 155 KgContract $40 Million+ from DARPA
Boston Dynamics - BigDog
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Boston Dynamics - BigDog
Boston Dynamics - BigDog
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Boston Dynamics - BigDog
SensorsI Joint positioningI Joint forceI Ground contactI Ground loadI Laser gyroscopeI Stereo vision systemI Internal sensors monitoring:
I Hydraulic pressureI Oil temperatureI Engine temperatureI RPMsI Battery charge
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Boston Dynamics - BigDog
Future goals:I Follow a soliderI Allow solider to specify distance to followI Move to solider to provide suppliesI Deviating from the soldiers pathI Move faster, longer, and be stronger!
Boston Dynamics - BigDog