Development of hybrid FES walking assistive system - Feasibility study-

We describes a feasibility study of the hybrid functional electrical stimulation (FES) walking assistive system, which is based on the fundamental principle of passive walking. The pilot gait study showed that the muscles involved in ankle push-off movements such as the soleus and gastrocnemius around the ankle joint, were stimulated in a chronic spinal cord injury subject, permitting the stimulated lower limb could move into the swing phase. Walking speed with the driving force was adjusted to be similar to the natural frequency range of normal gait. Stimulus strength was estimated online, based on the basis of a musculoskeletal model. Because main problems for FES is the the stability of the muscular force output, this issue was specifically investigated with regard to whether the processed electrical response (Mwave) of the stimulated muscle could be utilized as a force feedback signal. A clever adjustment of stimulating timing was introduced by to circumvent the interference of electrical responses due to multichannel muscle stimulations. We found that stable force outputs may greatly assist an effective pattern of passive walking.