Design of Robust H ∞ Controller based on Nonlinear Observer for Sensorless PMSM using LMIs

Permanent magnet synchronous motors (PMSM) are extensively used in industry due to their high efficiency, high power density, reliable performance, and simple structure. One of the problems in controlling these motors is the requirement of accurate information of their speed and position. Recently, due to the problems related to the speed sensors, the estimated values are used instead of measurements. Also, considering the presence of uncertainties in model parameters and load torque, velocity tracking performance has deteriorated in the previous methods. In this paper, a nonlinear observer-based robust control system has been designed using H ∞ methods to control PMSM without speed sensors. The stability of the proposed method has been proven using the Lyapunov theorem and the stability conditions have been written as linear matrix inequalities (LMI) to obtain coefficients. The simulation results show the proper tracking of arbitrary speeds with variations of load torque, motor parameters, and reference speed.