Identification of Wrist Elastic Moment in Healthy Subjects for Control by Functional Electrical Stimulation

Abstract

This study is for a functional electrical stimulation. Functional electrical stimulation is a system that uses electrical stimulation to generate specific joint movements. If the nerve is alive, it is possible to promote muscle contraction from the outside by electrical stimulation. If arbitrary movements are generated, to build a control system is necessary for functional electrical stimulation. A model of muscle contraction is needed for control using functional electrical stimulation. It is assumed that the control accuracy will be improved by incorporating the necessary information into the model based on human physiology. In this study, the angle-dependent term in the reaction during muscle contraction is focused as one of the necessary information characteristics. As the angle changes, the muscle condition changes, resulting in responses such as stretch reflexes and repulsive forces. This is important information because if such a response is not taken into consideration, an error will occur between the model and the actual output. In the conventional research, the angle-dependent term was identified by focusing on the lower limbs, and the parameter fitting was realized by using the double exponential function. In this study, the knowledge of the previous study is applied to the upper limbs to build a model. Since the response is different between the upper limbs and the lower limbs, the movements are not always the same. Therefore, verification was performed. From the experimental results, the model based on the double exponential function was a model that took individual differences into consideration even in the upper limbs.