A fuzzy backstepping controller for a pneumatic muscle actuator system

A nonlinear fuzzy backstepping controller is presented for set-point regulation of a pneumatic muscle actuator. Inflation and deflation are the two possible modes of operation of this actuator. Three fuzzy sets, one for each of both modes and one for the transition region, are considered. Each fuzzy set is associated with a local backstepping controller. At the inflation and deflation regimes, the associated controllers are exact backstepping controllers, whereas a robust nonlinear backstepping controller is used at the transition regime and deals with regime uncertainty. The use of fuzzy membership functions provides a smooth controller. The closed-loop system is globally and ultimately bounded.