Speed identification and control for permanent magnet synchronous motor via sliding mode approach

In this paper, speed identification and control problems are simultaneously considered for a permanent magnet synchronous motor (PMSM) based on the sliding mode technique. To eliminate the mechanical sensors, an observer is designed to identify the speed of PMSM based on a variable-structure model reference adaptive system, in which a sigmoid function with an adaptive gain is applied to replace the conventional signum function to cope with the chattering problem caused by the discontinuous switch function. Then, a sliding mode speed regulator is developed to overcome the limitations of traditional proportion integration scheme. Desired flexibility, adaptability and high precision are obtained and the stability of the closed-loop system is guaranteed by the proposed strategy. The results of simulation by MATLAB/Simulink indicate that the speed could be estimated and adjusted precisely, and the dynamical property of system is evidently improved.