MODELING AND NONLINEAR TORQUE CONTROL OF A SWITCHED RELUCTANCE MACHINE

The research of a control to reduce the torque ripple of a Switched Re luctance Machine (SRM) is the main aim of this paper. The SRM is very attractive because of its simple structure. Unfortunately, its polypha se torque is naturally pulsed because of the highly nonlinear electrom agnetic characteristics and because the phases have to be successively commutated in order to maintain a continuous rotation. First, the ele ctromagnetic characteristics (torque and flux with regard to the posit ion and the current) have to be very precisely determined. Several exp erimental methods of characterization are presented. A model based on this experimental electromagnetic characterization is necessary for th e synthesis of the control. The models found in the literature, compar ed with the experimental data, are not adapted to the SRM under study. An original model is then proposed. After defining an appropriate str ategy for the phase commutation, the limits of the classical linear co ntrol (Proportional Integral controller) are determined. In order to c ompensate the SRM nonlinearities, a nonlinear torque control has been simulated and tested. Very promising results have been obtained at low and medium speeds.