Performance comparison of sliding mode control with PI control for four-quadrant operation of switched reluctance motors

In this paper we present a performance comparison of conventional PI control and nonlinear sliding mode control for switched reluctance motors (SRMs). A feasible low cost nonlinear controller is then suggested for high performance speed regulation control of the SRM for direct-drive servo applications. We present the design of a robust sliding mode controller based on a nonlinear mathematical model (which takes magnetic saturation into account) of the SRM. Instead of decoupled control as proposed by previous researchers which requires m voltage regulators (choppers) for a m-phase motor, we propose to use only one voltage regulator in this work. This will reduce the cost of the drive system significantly. A multi-phase-excitation scheme is adopted in our controller design for the purpose of exploiting higher power as well as minimizing torque ripple. Simulations for the drive system have been carried out. Robustness is tested against the most critical parameter uncertainties such as phase resistance. A robust ripple-free nonlinear controller is achieved for the SRM drives, whose performance outweighs that of the PI controller.