On friction and disturbance-compensation based control design for PMSM servo system

In this paper, the position control problem of high-precision permanent magnet synchronous motor servo system is studied. From improving the system low velocity performance and disturbance rejection property point of view, a compound control method, which combines model-based friction compensation with disturbance observer compensation, is designed for speed loop based on PI control strategy. First, the system friction is modeled by Stribeck friction model, whose parameters are identified offline by using genetic algorithm, and the feedforward compensation is presented using the estimated value of the identified model. Subsequently, a disturbance observer is used to estimate the uncertainties caused by modeling errors, friction over-compensation or less-compensation and external disturbance, and then this observed value is used to construct further feedforward compensation. Simulation results show that the proposed method can reduce the influence of the friction nonlinearity on the low velocity performance of servo system and improve the system tracking accuracy and disturbance rejection property.