Sliding-Mode Observer for Estimating Position and Speed and Minimizing Ripples in Rotor Parameters of PMSM

A sliding-mode observer (SMO) has been designed and implemented in this paper for the sensor-less speed control of three phase permanent-magnet synchronous motor (PMSM). The designed SMO substitutes the conventional switch function with a sigmoid function to reduce system chattering. In order to minimize ripples, present in torque and speed of PMSM, two Proportional-integral (PI) controllers are utilized. The SMO is designed based on back EMF model by which speed and position of permanent magnet rotor are computed. This helps eradicate the phase compensation module and the low pass filter and accuracy of estimating the parameters is improved. Simulation results of the designed SMO algorithm are presented and the reduction in ripples of motor parameters are demonstrated.