Feedback control systems for FES walking must take
into consideration muscle latencies and the timescale of the
desired gait. The time delay between stimulation and muscle
force production (100-300 msec) may be long compared to the
time spent in certain limb postures during gait [2]. By thC
time the effect of the stimulation can be observed, it is too
late to modify the it; the stimulation for future motions is
already being sent. For this reason, the control system under
development operates at the slower timescale of the gait
cycle. This next-step, or cycle-to-cycle controller modifies the
stimulation pattern for future gait cycles depending upon
observations of the previous gait cycles.