On the appropriate uses of fuzzy systems: fuzzy sliding mode position control of a switched reluctance motor

The use of switched reluctance motors in position servo applications is complicated by their non-linear torque production characteristics. In this paper, the use of fuzzy logic to overcome this problem is described. The approach taken is that of exact input-output linearisation of the non-linear motor characteristic using a fast inner control loop in conjunction with a slower outer position control loop. The application of adaptive fuzzy systems to learn the input-output linearisation characteristic for a motor has been reported previously. This paper is concerned with the design of an outer, fuzzy logic based, position control loop. Fuzzy controllers are compared and contrasted with linear controllers and with non-linear sliding mode controllers. Experimental results from a 4 kW four phase switched reluctance motor using a fuzzy controller that is equivalent to a simple sliding mode controller are presented and the applicability of fuzzy logic to this control problem is discussed