Efficient Bipedal Robots Based on PassiveDynamic Walkers Review

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• Efficient Bipedal Robots Based onPassive-Dynamic
  Walkers Review
• Jianhua (Sam) Xie
• 05172055

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Overview

• Passive-dynamic walkers
• They are simple mechanical devices, composed of
  solid parts connected by joints, that walk stably
  down a slope.
• They have no motors or controllers and can have
  humanlike motion

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Overview-Different approach

• Most researcher study human walking by measuring
  joint angle and reaction force
• passive-dynamics model compares to human in terms
  of morphology, gait appearance, energy use, and
  control
• The robots do not control any joint at any time

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Overview

• The article present three robots based on
  passive-dynamics, with small active power sources
  substituted for gravity, which can walk on level
  ground.
• These robots use less control and less energy
  walk more naturally

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Passive designs

• The Wilson Walkie
• MITs improved version
• Cornell copy of McGeers capstone design
• The Conell passive biped with arms

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Three Robots Developed

• Three robots using passive-dynamic machines were
  built in at three institutions
• The Cornell biped (A)
• The Delft biped (B)
• MIT learning biped (C)

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The Cornell biped

• Machine weight 12.7kg and has 5 internal degrees
  of freedom
• The robot has only one capability, walking
  forward
• Low energy use (primary goal)
• A proof-of-concept prototype

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The Cornell biped

• The Cornell biped is specifically designed for
  minimal energy use.
• The primary energy losses for biped walking at a
  constant speed is due to dissipation
• Cornell design demonstrates that its possible to
  avoid this negative actuator work

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The Cornell biped - how to walk

• One hip, two knees, and two ankles
• Ankle push-off restores energy lost
• State switching
• Left Leg Swing
• Right Ankle Push-off
• Right Toe Return
• Right Leg Swing

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The Delft biped

• Machine weight 8kg and has 5 internal degrees of
  freedom
• Air-actuated artificial muscle (McKibben muscles)
• A proof-of-concept prototype

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The Delft biped

• The muscles are fed with CO2 from a 58 atm
  cannister, pressure-reduced in two steps to 6 atm
  through locally developed miniature pneumatics

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The Delft biped

• The success of the robot at balancing using
  ankles
• swift swing-leg motion not only increased
  fore-aft stability but also increased lateral
  stability

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MIT learning biped

• Machine weight 2.57kg and has 6 internal degrees
  of freedom
• The robot is designed to test the utility of
  motor learning on a passive-dynamic mechanical
  design.

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MIT learning biped

• The goal of the learning is to find a control
  policy that stabilizes the robots trajectory on
  level terrain using the passive ramp-walking
  trajectory as the target.

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MIT learning biped

• Measurements from previous and current step to
  efficiently estimate the performance gradient on
  the real robot
• despite sensor noise
• imperfect actuators and uncertainty in the
  environment

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MIT learning biped

• The MIT biped shows that the efficiency of motor
  learning can be strongly influenced by the
  mechanical design of the walking system, both in
  robots and possibly in humans.

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Three robots mimic humans

• Each of robots here has some design features that
  are intended to mimic humans
• Cornell and Delft use anthropomorphic geometry
  and mass distributions in their legs and
  demonstrate ankle push-off and powered leg
  swinging
• MIT biped uses a learning rule that is
  biologically plausible at the neural level

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Conclusion

• The conclusion that natural dynamics may largely
  govern locomotion patterns was already suggested
  by passive-dynamic machines.