A preliminary evaluation of linear control schemes for FES-assisted movements

Functional Electrical Stimulation (FES) can be used to revive movement functions of the human body to a certain degree which was lost due to occurrences of the nervous system disorders resulting from accidents or diseases. It can also be employed for gait rehabilitation as well as therapy. Control systems could be employed to improve on the FES-induced motion, and the closed-loop was targeted due to its advantages. Based on the papers reviewed, studies have shown that the linear control schemes are popular for movement restoration in the lower limb, but mostly for continuous standing contributing to mainly the stance phase. Therefore, a myriad of limitations was observed which include: the need for using improved sensors, re-tuning for every subject, tests conducted using patient with more straightforward ailments, complexity in implementation and most importantly is the issue of stability. The swing phase of gait movement and the full walking motion have more complex dynamics and coupled with the nature of the plant (human with nervous system disorder and the neuromuscular structure) could render the linear control method obsolete or unsuitable. Hence, there is a need to investigate other techniques such as the nonlinear and intelligent control methods.