The development of powered orthoses and exoskeletons for robotic gait assistance has led to new issues related to their control. Limited work has been published regarding when to provide plantarflexor torque to the ankle [1–3]. If actuation is given too early, four times more energy for walking may be necessary [1]. Some groups have followed a functional approach and used minimization of metabolic cost as the optimization criteria for detecting appropriate plantarflexor actuation timing (e.g., see Ref. [2]). Optimizing timing using metabolic data can be time-consuming (10 s of minutes of walking). In addition to functional energetics, the effect of these devices on joint biomechanics should also be considered.
The portable powered ankle foot orthosis (PPAFO) is capable of providing both plantarflexor and dorsiflexor torques by using a pneumatic rotary actuator at the ankle [4]. The PPAFO has three sensors:...
