Experimental investigation of variable structural PID control for switched reluctance motor drives

Abstract

In this paper we present the performance of a variable structural PID control as applied to a switched reluctance motor (SRM) for speed control application. The SRM usefulness as a servo has been limited due to its strong nonlinear electromechanical characteristics which result in significant torque and hence speed ripples. It has been shown that conventional fixed gain PI controller is not able to meet stringent requirements of servo systems. This paper describes the design method of a variable structural PID (VSPID) control system. In this controller, the PD mode is used in the case of large errors to speed up the response, whereas the PI mode is applied for small error conditions to eliminate the steady-state offset. Flexible changes of the controller structure from PD to PID to PI mode and resilient controller parameters of VSPID during the transient could thereby solve the typical conflict in nature between steady-state error and dynamic performance. Hardware implementation of VSPID controller has been achieved using Texas Instrument's TMS320C50 Digital Signal Processor. Experimental results obtained for speed control of SRM show improvements over conventional fixed gain PI controller.