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.