High-precision control for functional electrical stimulation utilizing a high-resolution encoder

Abstract

In functional electrical stimulation, the time delay between an input voltage and the corresponding muscle force is a significant issue. This study revealed that the joint angle/voltage relationship can be modeled as a fourth-order system. This enables the inclusion of a time delay in the high-order phase delay of the force/voltage relationship, which may lead to delay recovery using a suitable controller. Accordingly, a full state feedback controller is proposed in this study, to recover the phase delays. Jerk measurement is mandatory for full state feedback controllers owing to the joint the fourth-order joint angle/voltage relationship. This issue can be solved by the recent development of high-resolution encoders. Finally, the validity of the proposed method was verified experimentally.