Second level state observer of current and position for permanent magnet synchronous motor on AC control system model

The voltage control model and the rotor kinematic model of PMSM(permanent magnet synchronous motor) are analyzed to improve the feedback accuracy of servo control system and to solve the delay problem of feedback signal. The analyzing results are further used to analyze the work timing of control system's feedback loop and the number of hysteretic cycles is obtained. Then, a first level state observer of current and position for PMSM is proposed. The current and position values in the current control cycle are used to obtain accurate estimations of the current and position values in the next control cycle, and the observation output of the first level state observer is served as the input of the second level state observer so that the high frequency oscillation and the time-delay of the current and position's feedback signal can be further suppressed. Results show that the second level state observer of current and position has a significant inhibition on the high frequency noise and an accurate prediction on the feedback value. The observation error of the second level position is less than 0.005 rad, and the high frequency noise included in feedback has is eliminated. When the proposed method is applied in an AC servo control system for position control with high speed and high response, the response frequency of the system reaches 200 Hz, and acceleration arrives at 62 831 rad/s², and its positioning accuracy is 1.5, while the system's phase current is stable. It can be concluded that the proposed method realizes the accurate observation on current and position values.