Abstract：Aiming at the deterioration of position control performance in the position servo system of

permanent magnet synchronous motor（PMSM）due to internal and external disturbances such as load torque

variation，an optimal position control method was proposed with anti-disturbance capability on the basis of active

disturbance rejection control mechanism. First，a third-order nonlinear extended state observer was established to

estimate the generalized disturbance and the original system was dynamically compensated according to the

estimated value，which effectively improved the anti-disturbance ability of the position servo system. Then the

controller was designed based on the idea of the fastest control synthesis function of the discrete second-order

integral series system，which optimizes the dynamic performance of the position control in the servo system.

Simulation results show that the proposed method can maintain the good position control performance when the

motor parameters were perturbated or the load torque was suddenly applied.

      Key words：permanent magnet synchronous motor（PMSM）；nonlinear extended state observer；linearization via dynamic compensation；optimum control；double close-loop position control