Fuzzy controller can be useful to realize a practical closed-loop FES controller, because it is possible to make it easy to design FES controller and to determine its parameter values, especially for controlling multi-joint movements by stimulating many muscles including antagonistic muscle pairs. This study focused on using fuzzy controller for the closed-loop control of cycling speed during FES cycling with pedaling wheelchair. However, a designed fuzzy controller has to be tested experimentally in control performance. In this paper, a closed-loop fuzzy FES controller was designed and tested in knee extension movements comparing to a PID controller with healthy subjects before applying to FES cycling. The developed fuzzy controller showed good control performance as a whole in comparing to PID controller and its parameter values were determined through simple control tests of the target movement.

Rehabilitation training with pedaling wheelchair in combination with functional electrical stimulation (FES) can be effective for decreasing the risk of falling significantly. Automatic adjustment of cycling speed and making a turn without standstill has been desired for practical applications of the training with mobile FES cycling. This study aimed at developing closed-loop control system of cycling speed with the pedaling wheelchair. Considering clinical practical use with no requirement of extensive modifications of the wheelchair, measurement method of cycling speed with inertial motion measurement units (IMUs) was introduced, and fuzzy controller for adjusting stimulation intensity to regulate cycling speed was designed. The developed prototype of closed-loop FES control system achieved appropriately cycling speed for the different target speeds in most of control trials with neurologically intact subjects. In addition, all the control trials of low speed cycling including U-turn achieved maintaining the target speed without standstill. Cycling distance and cycling time increased with the closed-loop control of low cycling speed compensating decreasing of cycling speed caused by muscle fatigue. From these results, the developed closed-loop fuzzy FES control system was suggested to work reliably in mobile FES cycling.