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