Evolution of intelligent and nonlinear control approaches for FES induced movement generation of the lower limb

Achieving automated control of FES induced walking had been a challenge for control system engineers. This work examines control efforts in FES aided movement applications with the aim of identifying a gap in knowledge that would create an impact towards solving or getting closer to total approval for clinical usage, easy to understand and use, simple, faster implementation and with high regards to safety. Effort was made to use all available means within reach and are close to works on restoration of gait control with emphasis on the lower limbs. FES can be applied alone (pure), but for walking or other active exercise it is usually combined with orthosis (hybrid). Nature of the plant which is a combination of the nervous, muscular and skeletal (neural-muscular-skeletal) systems as well as of limitations in sensor availability made the linear approach not favorable to such systems. Intelligent strategies most likely could provide clinically acceptable solutions, but are likely to face stability issues which are serious concern in this scenario, other shortcomings include longer tuning duration, re-tuning for different subjects and involvement of high computation. Stability issues can be dealt with directly when nonlinear techniques are used and also periodic utterances can be handled with relative ease. Nonlinear control techniques share the shortcoming of high computational requirement and at times complexity problems with the intelligent schemes, but kudos to achievements in microprocessor technologies that always yields higher capability processors which could eradicate issue. Hence, exploring the nonlinear technique could provide solution which could pave way for making countless things easy. That is; more impact could be made by understanding fundamentals or revisiting fundamental studies on nonlinear control for this application.