Research on friction compensation for PMSM servo systems

Friction is one of the main factors decreasing tracking precision for servo system at low speed or back-forth-movement. To reduce the influence of friction on the system, a compound compensation strategy based on Stribeck model and GPI observer is designed in this paper. Firstly, g-axis current and speed information are sampled. Then, genetic algorithm is used to identify the model parameters. At last, on-line friction compensation is added on the servo system based on the identified model. Due to the variation of the operating conditions, the compensation of the friction model based on the nominal working condition has a deviation. Considering friction compensation model error does not belong to the slow and constant disturbance, which is more suitable for the processing of polynomial form. Therefore, a GPI observer is designed. Simulation results are provided to demonstrate the proposed control method can effectively improve the flat top phenomenon in position tracking and dead zone phenomenon in speed tracking.