Sensorless Control of PMSM Based on Sliding Mode Observer

A novel sliding mode observer(SMO) of PMSM(permanent magnetic synchronous motor) was presented, which estimated the rotor position and angular velocity accurately.The proposed SMO substitutes a sigmoid function for the conventional signum function with a variable boundary layer which is changed according to the rotational velocity.The dependence to motor parameters and chattering effects that is commonly found in signum function using for the switching function were overcome.By combining the model of PMSM under d-q coordinate,the convergence condition of observer was deduced.The convergence was verified by the Lyapunov theory.Simulation results show that the rotor position and velocity can be observed accurately,and also has good dynamic performance and robustness.