Selective Drive and Control of Index Finger Joint Using Multipoint Functional Electrical Stimulation

Functional electrical stimulations (FES) drive human joints by stimulating peripheral nerves electrically. FES is applied to the rehabilitation of paralyzed patients or force feedback applications. However, exerting a large force to a specified finger using FES is difficult, because high-intensity stimulation can cause low selectivity. This problem is remarkable for the index finger because its fascicles are distributed deep in the forearm with a small area close to the skin. This paper describes a method for simultaneously stimulating multiple points to solve the problem. We conducted experiments focusing on selectivity and exerting torque to the index finger. The phase difference between stimulation waveforms and electrode isolation states were varied in the experiments. The proposed method was confirmed to induce a larger force than one-point stimulation and did not deteriorate selectivity if appropriate parameters were selected. Moreover, a finger angle control experiment considering selectivity was conducted. The selectivity problem makes selective control difficult. The proposed method was advantageous for finger controlling.