Application of nonlinear control to switched reluctance motors: a feedback linearisation approach

The design of a feedback linearisation (FBL) controller for switched reluctance (SR) motor is presented. The mathematical model of the motor takes magnetic saturation into account. It has been shown through simulation studies that a FBL controller based on a linear control law provides better dynamic performance in comparison with a PI controller. However, the FBL controller based on a linear control law alone is not adequate to handle uncertainty in the SR motor model, and hence the corresponding torque ripple is substantial. To reduce torque ripple in the drive system the design of a robust FBL controller based on Lyapunov's second method, which takes care of model uncertainty is presented. Out of the three input variables to the SR motor, phase voltage, on-angle and off-angle, the phase voltage is used as the manipulated control variable in the drive system. Performance of the nonlinear model together with the robust FBL controller for a speed control application is examined through digital simulation. Simulation results obtained confirm reduction in torque ripple, improved transient and steady-state performance and robustness of the controller to parameter variations under various types of disturbances.