Figure 7. Impedance control law used during walking trials.

Desired torque is a piecewise linear function of ankle position, with separate dorsiflexion (negative velocity) and plantarflexion (positive velocity) phases. Gray lines indicate programmed trajectories for each condition, with darker lines corresponding to conditions with higher prosthesis push-off work. Plantarflexion segments were manipulated across conditions to alter the net positive ankle joint work over the step cycle. Dashed line indicates biological ankle joint power measured in [38].