While such phase plots are useful tools for observing limit cycle behaviour in a system, they tell

us relatively little about the difference between sampling strategies and/or the visual appearance of

the walk.

The graphs shown in Figure 4.3 provide additional information. Graphs (a), (c) and (e) show the

effect of various choices for Q^d
, in particular, for the forward component of Q^d
. The trials explore

the useful range of this parameter by uniformly sampling a broad set of values. For each trial, the

forward component of the Q^dis held constant for all steps.

The lateral component is fixed at 0.0

for all trials.

Walks are up to a maximum of 60 steps long and fewer than 60 successful steps

indicates a fall.

The "hip plots" corresponding to the most successful trials for each sampling strategy are shown

in Figure 4.3 (b), (d) and (f). Hip plots indicate the position and orientation of the biped's pelvis

in the horizontal plane as viewed from above.

This orientation information indicates the direction

the biped is facing as it walks, allowing a forward motion to be easily distinguished from a lateral

(sidestepping) motion.

The lines on the plots are approximately 1 meter in length, significantly

wider than the biped's actual hips so that their orientation can be easily seen.

This affects the

perceived scale of the plot, making the walks appear

shorter

than

they

actually

are.

The

dimensions of the terrain are given in meters.

hip plots is approximately 0.16 seconds.

The elapsed time between adjacent samples on the