Figure 2.

Diagram of state machine used to provide a biological hip torque profile. (A) Early stance phase (detected at the heel contact event) activated a hip extension torque. A transition to mid stance occurred at approximately 20% of the gait cycle. Mid stance was unpowered. A transition to late stance occurred at approximately 35% of the gait cycle. Late stance activated a hip flexion torque. Toe off triggered a transition to swing phase which was not actuated. (B) States relative to the ground reaction force profile (normalized to body weight). A threshold trigger switched the states between stance and swing phase (15% of body weight). Mid stance was triggered based on a decrease from the first peak in the ground reaction force profile. Late stance was triggered based on an increase in the ground reaction force profile from the trough.