Sensorless Control of a Switched Reluctance Motor by Using Sliding Mode Observer

This paper presents a sliding mode observer for sensorless operation of SRM (switched reluctance motor) drive. Design of such an observer depends mainly on the nonlinear model of SRM. In this technique, neither extra hardware nor huge memory space arenot required but it only requires active phase measurements. Furthermore, PI (proportional integral) are suggested to operate individually along with the SMO (sliding mode observer) to cover a full speed range of sensor less controller. Both controller schemes operate in PWM (pulse width modulation) control mode. The proposed observer is implemented and using Matlab/Simulink. All results obtained with simulation are presented. . INDEX TERM: Switched reluctance motor, sliding mode observer, PI controller I.INTRODUCTION In recent years, the SRM (switched reluctance motor) has received considerable attention in variable speed drive applications. Its simple construction due to the absence of the magnets, rotor conductors, brushes, and high system efficiency over wide speed ranges make the SRM drive an interesting alternative to compete with permanent magnet brushless DC motor and induction motor drives [1, 2]. However, the speed control of the SRM is not yet a perfected art. The controllable variables of the SRM are the phase current magnitude (i), the turn on angle (α), and the turn off angle (β) [3, 4]. For sensor less operation of SRM, generally speaking, there are two basic types of position estimation methods, active probing and nonintrusive estimation. In active probing, special testing signals are injected into an unenergized phase. The position-dependent information is extracted by additional decoding circuit. In nonintrusive ways, the dependence of phase current and phase winding flux linkage or inductance on rotor position is utilized [5-8].Recently, intelligent estimation techniques SMO(sliding mode observer) have been used in rotor position an speed estimation. However, offline training based on prestored data is required [911]. The use SMO based model has been investigated for the indirect position sensing in SRM drives [12-14]. For estimating the rotor position and speed in this application, the observer requires only terminal measurements of voltage and current. The implementation of the observer generally involves the use of a microcontroller or a digital signal processor. Still, the observer-based approach is relatively simple and can be inexpensive compared to the alternative sensor less diagnostic methods based on pulse injection. Optimal performance of the drive may be described by different figures of merits, such as drive efficiency,