90

(a)

(b)

(c)

t

As the sequences of Figure 5.13 indicate, the peak height of the swing knee in each step increases

with hold time. This is due to an associated increase in stance hip pitch.

The increased hip pitch

is automatically introduced by the balance control in order to meet Q^dat the end of each step.

Without this action the biped would fall due to leaning too far forward with larger hold times or

too far backward with smaller hold times.

The increased hip pitch gives the walk a more

mechanical, "marching" appearance at lower step rates than at higher step rates.