89

angle. The minimum distance to the current target point before changing to the next target point in

sequence is chosen to be slightly larger than the tightest turning diameter.

scenarios where the biped indefinitely walks in circles around a target point.

This helps avoid

transition
info

DOF:

state

1

0
0
0
0
0
0

2

0
0
0
0
0
0

3:0

0
0
0
0
0
0

3:1

0
0
0
0
0
0

3:2

0
0
0
0
0
0

4

0
0
0
0
0
0

5:0

0
0
0
0
0
0

5:1

0
0
0
0
0
0

6:0

0
0
0
0
0
0

6:1

0
0
0
0
0
0

6:2

0
0
0
0
0
0

7

0
0
0
0
0
0

8:0

0
0
0
0
0
0

8:1

0
0
0
0
0
0

S1
S2
S3
S4
S5
S6

0
.05
.05
0
.05
.05

^{, stride rate perturbation for human model with ball-}

Stride Rate Perturbation

5. 4

The stride rate perturbation can be used to vary the stride rate of the biped.

The perturbation,

shown in Figure 5.12, modifies only the hold times of particular states in the

base

PCG.

Applying the perturbation with a positive scaling parameter increases the hold time in each state,

resulting in a decrease in stride rate.

Applying a negative scaling parameter has the opposite

effect, decreasing the hold time in each state and the increasing stride rate.

The unperturbed walk

is a straight walk with a stride rate of 1.0 strides/second and uses torso servoing and speed control

with a composite RV³.

Figure 5.13 (a), (b) and (c) show three distinct steps in which the perturbation is applied with a

gain of -1.0, 0 and +1.0 respectively to obtain stride rates varying from 0.8 strides per second to

approximately 1.25 strides per second. The three sequences are in fact taken from a single walk,

during which the stride rate is dynamically varied.

for each unit of change in the perturbation gain.

In this case, stride rate transitions use 3 steps

3_{In this case, an up vector-based forward RV component and a swing-COM-based lateral RV component.}