Research On The Servo Control System Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM) with the advantages of simple structure, small rotation inertia, high efficiency, high power density and good control performance and so on, is gradually replacing other motors as the actuator institution of servo control system and the high performance servo system control of PMSM has become the research hotspot in recent years. The three closed-loop control of the servo system based on PMSM is researched in this paper; the low speed stability and the position following performance of the servo system are analyzed and corresponding control methods are researched.Firstly, the mathematical model and vector control principle of PMSM are analyzed. Among that, id=0 control and the maximum torque per ampere(MTPA) control are suitable for the servo control system which is designed in this paper. Traditional MTPA control algorithm which used in the system will lead to large result error and large calculation when motor parameters are changed is researched. The idea of general signal injection method is that the torque to current vector angle of the partial derivative is zero in the MTPA operating point. Sliding discrete fourier transform(SDFT) which can extract the specified frequency signal is applied to simplify the extraction of injection signal and change the control structure to make it more convenient to design the servo control system and improve the MTPA control algorithm.Secondly, the closed-loop control structure of PMSM servo system is designed with id=0 control, and the detailed design process of the current loop, speed loop and position loop and its regulator parameters are presented. The integral saturation problem of the speed loop PI regulator is studied. The influence of the integral limiting and the anti windup method based on the inverse calculation are analyzed, and an improved anti windup PI regulator is designed. The stability of low-speed servo system is mainly affected by the influence of disturbing torque and rotate speed measuring precision, improved design of disturbance torque observer is used to observe the disturbance torque. Torque current compensation can restrain the disturbance, and the first order low pass filter can improve calculation precision at low speed. The low speed stability is overall improved.Thirdly, the position feedforward control is used to improve the response speed of the slope position signal, the following speed and error of the control system are better than the pure proportional control. For the problem of large error of periodic position signal and slow response, embedded repetitive controller is designed based on the internal model principle. Combined with the high heels of repetitive control with the precision and scale control of fast response, the response speed of sinusoidal periodic signal response speed and tracking precision is overall improved. The advantages and stability of embedded repetitive control structures are analyzed, on which basis, auxiliary compensator Q(z) and compensator C(z) of the repetitive controller are designed, and the position feedforward control is used to replace the proportional control to further improve the performance of embedded repetitive controller.Finally, PMSM servo control system hardware platform is built based on existing laboratory resources, and DSP algorithms are designed. Improved MTPA control experiment, id=0 vector control experiment, position servo control experiment, position feedforward controller experiment and embedded repetitive controller experiment are finished. The experimental analysis shows that the algorithm is viable and effective.