Self-tuning sensorless SRM drives for low cost mass production

In this paper, a modified amplitude modulation based sensorless control method for switched reluctance motor (SRM) drives with optimal performance is presented. The sensorless method used offers very high resolution comparable to that of resolvers and with this method, closed loop speed control is achieved. Torque per ampere has been chosen as a performance index and is used for optimization purposes. Through detailed simulation of the drive system using a dynamic model, the existence and uniqueness of an optimal set of control variables is shown. A fast converging unidirectional search scheme is used for optimizing the phase currents to achieve maximum torque per ampere. The dynamic performance of the drive system with optimization incorporated is simulated with the model and the simulation results are presented. The proposed method is implemented on a 500 W, 100 V, 6/4, three-phase SRM drive for validation purposes. Using the proposed sensorless control method, speed control over a wide range has been achieved and the results are presented. The corrective measures to be taken in order to achieve sensorless operation with accuracy and also optimal performance in the presence of parameter variations caused due to manufacturing tolerances or aging are addressed. A brief analysis on the important attributes like resolution, accuracy, speed range and transient stability of the proposed sensorless method is also presented.