Implementation of Cycle-to-Cycle Control with Energy Storage Element for FES-Assisted Elliptical Stepping Exercise

Rehabilitation exercise with the use of functional electrical stimulation (FES) has become one of the effective technique of rehabilitation for hemiplegic and other neurological disorder conditions. Control is among the main issues in FES since muscle response is highly dynamic due to fatigue and other reasons. Different way of FES application may come with different structure of control technique. In this work, fuzzy logic controller (FLC) based cycle-to-cycle control with an energy storage element was designed and implemented for FES-assisted elliptical stepping exercise. The aim is to obtain appropriate control performance by combining the control action of FLC cycle-to-cycle control and effect of the energy storage element. The energy storage element makes use linear extension spring that provide resist and assist action to the exercise movement. Thus, instead of control action that totally rely on the FLC cycle-to-cycle control, the energy storage element could provide additional assistance in improving the exercise performance. Analysis was conducted to determine the appropriate spring length and constant. Comparison of performance with the FLC cycle-to-cycle control without the energy storage element was also conducted. The result showed a promising performance and hence supports the potential use of the proposed control technique for FES-assisted elliptical stepping exercise.