A study on modification method of stimulation patterns for FES

Functional Electrical Stimulation (FES) is efficient for restoring motor functions of paralyzed extremities by upper motor neuron disorders. An adequate set of time series of stimulus intensity to each muscle is necessary to restore desired motion by FES. With regard to the system commercially available in Japan, stimulus data that we call 'stimulation patterns' are prepared and stored into the system before restoration. If patients wish to realize much better motion, it is desirable to modify the stimulation patterns. Considering their independent lives, it is very important to modify the patterns by themselves. The purpose of this study is to develop a new FES system with modification capability of the shapes of stimulation patterns. Since numerous patients have little medical knowledge about musculoskeletal system, the FES system was designed to be operated by selecting simple commands (for example, 'upward'). First of all, we proposed an adjustment method of stimulus voltage using a generalized inverse matrix of the matrix describing muscles' function. Secondly, based experimental results to control wrist angles of normal subjects showed that stimulus voltages to multi- muscles were adjusted with this method. Thirdly, we developed a system that could modify stimulation patterns with the simple commands on these experimental bases. Experimental results of controlling normal subjects' wrist angles show that the user could modify stimulation patterns with this system.