Legged Robotics & BigDogjmconrad/ECGR6185-2008-01/notes/Big… · Schmidt: Legged Robotics & BigDog...

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Legged Robotics & BigDogMarc Raibert: Boston Dynamics

Andy SchmidtUniversity of North Carolina at Charlotte

April 16, 2008

Boston Dynamics - BigDog


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



Raibert’s Legged Robotics Paper

Pitfalls:I Joint movementI BalanceI Current and future foothold calculations



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



General Electrical Legged Truck



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



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



Marc Raibert’s One Legged Robot



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

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 - DI Guy




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




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




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




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!


Legged Robotics & BigDogjmconrad/ECGR6185-2008-01/notes/Big… · Schmidt: Legged Robotics & BigDog...

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Transcript of Legged Robotics & BigDogjmconrad/ECGR6185-2008-01/notes/Big… · Schmidt: Legged Robotics & BigDog...