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Evolutionary RoboticsBipedal Locomotion
Question 1:
Why only walking and running?
Question 2:
What (if any) partdoes the upper bodyplay in bipedal locomotion?
Evolutionary RoboticsBipedal Locomotion
Question 1:
Why only walking and running?
Question 2:
What (if any) partdoes the upper bodyplay in bipedal locomotion?
Honda’s ASIMO robot
CS295/CS395/CSYS395 Evolutionary RoboticsBipedal Locomotion
Passive Dynamic Locomotion
Steve Collins, Martijn Wisse,Andy Ruina, Cornell
Hybrid Dynamic Locomotion
Martijn Wisse, TU Delft (2004)
Evolutionary RoboticsBipedal Locomotion
Research question:
Can passive dynamic walkingbe evolved? How?
Could evolved passivedynamic walking beevolved further intohybrid dynamic walking?
Vaughan, E., Di Paolo, E., Harvey, I. (2004)The evolution of control and adaptation in a 3D powered passive dynamic walker.In Artificial Life IX, pp. 139-145.
Evolutionary RoboticsBipedal Locomotion
Research question:
Can passive dynamic walkingbe evolved? How?
Could evolved passivedynamic walking beevolved further intohybrid dynamic walking?
Vaughan, E., Di Paolo, E., Harvey, I. (2004)The evolution of control and adaptation in a 3D powered passive dynamic walker.In Artificial Life IX, pp. 139-145.
Vaughan, E., Di Paolo, E., Harvey, I. (2004)The evolution of control and adaptation in a 3D powered passive dynamic walker.In Artificial Life IX, pp. 139-145.
Mw = waist massMt = thigh massMs = shank massMf = foot massL = leg segment lengthXt = thigh mass x-offsetYt = thigh mass y-offsetXs = shank mass x-offsetYs = shank mass y-offsetLf = foot lengthW = waist radiusBy = starting hip angle
around y-axis
Vaughan, E., Di Paolo, E., Harvey, I. (2004)The evolution of control and adaptation in a 3D powered passive dynamic walker.In Artificial Life IX, pp. 139-145.
Placing the robot’s body under evolutionary control: evolve not just NN parameters, butbody parameters as well.
Ax = ankle spring/damperaround x-axis
Kx = knee spring/damperaround x-axis
Hx = hip spring-/damperaround x-axis
Hy = hip spring/damperaround y-axis
Ay = ankle spring/damperaround x-axis
Each spring/damper hastwo parameters: stiffness and damping coefficient
Q: How many body params?
Vaughan, E., Di Paolo, E., Harvey, I. (2004)The evolution of control and adaptation in a 3D powered passive dynamic walker.In Artificial Life IX, pp. 139-145.
Placing the robot’s body under evolutionary control: evolve not just NN parameters, butbody parameters as well.
High stiffnessLow stiffnessBlack line: low damping; blue line: high damping
Continuous Time Neural Network(CTNN)
Five motors: one attached to each
spring/damper.CPG =
Two hidden nodes / per motor
Sensors:*A = angle sensor what is the angle of the joint?*F = force sensor how far is the spring from its resting length?rot* = rotation about * axisaccel*=acceleration about * axis
motorshidden
sensors
The Fitness Function:
Q: Does d, t, x, z, r, or yreward or punish?
f: fitness
d: distance travelled
t: torque used(torque = rotational force)
x: hip rotation about x-axis
z: hip acceleration about z-axis
r: feet rotation about z-axis
y: hip rotation about y-axis
Shaping:
1. Evolve passive walking
2. Evolve hybrid walking3. Evolve sensor-based
walking
Shaping:
1. Evolve passive walking2. Evolve hybrid walking
During evolution: Evolve CPGmotor params Evolve body params Add (1/(1+v)) to fitness function v = difference between passive and hybrid velocity Gradually lower declined plane over generations
During evaluation: Record time to first heel strike Use this to set CPG frequency
3. Evolve sensor-based walking
Shaping: 1. Evolve passive walking2. Evolve hybrid walking3. Evolve sensor-based
walking
During evolution: reconnect sensors to NN with small connection weights Evolve all NN param weights Evolve body params Use 1/(1+v)
During evaluation: Same as before.
Robustness to external perturbations
Evolve for another 100 generations.
Small random force vectors applied to the robot while it moved (i.e. “wind”).
“Developed dynamic mechanisms to adapt to noise.”
“When pushed too far to oneside, the machine was observedto adjust its foot placement bystepping inward to regain balance.”
Robustness to internal perturbations
Evolve further.
Introduce “mistakes” whenbuilding the body.
Random changes are made to the body params
Robustness to CPG perturbations