Research On Low-speed And High-stability Permanent Magnet Synchronous Motor Servo System

Due to its high power density,high efficiency,high reliability and simple structure,permanent magnet synchronous motor(PMSM)servo system has been widely used in daily life,aerospace,weapons and other fields.When the servo system runs at low speed,due to the limitation of the resolution of position sensor,the enhancement of external disturbance and the non-linearity of the system,the motor speed fluctuates greatly,which affects the stability of the system at low speed,and limits the improvement of the steady-state and dynamic performance of the servo system at low speed.Therefore,the influence of disturbance torque on the system at low speed is analyzed and studied in this paper.On this basis,a certain control strategy is adopted to suppress the speed fluctuation of the motor at low speed and improve the speed tracking performance.Aiming at the speed fluctuation caused by load fluctuation,friction moment variation and cogging torque and electromagnetic fluctuation moment of motor at low speed,the feed-forward control strategy of disturbance torque observer is studied.The disturbance torque observer based on low-pass filter needs to differentiate the velocity.In order to reduce the magnification of error and the high-frequency noise caused by differential operation,a non-linear disturbance torque observer is designed.Nonlinear disturbance torque observer does not need differential calculation of velocity,which effectively improves the response speed of observer and the stability of observation results.Furthermore,the parameter selection of the observer is analyzed,and the model reference adaptive method is adopted to identify the motor inertia,so as to improve the accuracy of the observation results.In order to solve the problems of the speed detection delay and error of permanent magnet synchronous motor servo system at low speed,the software demodulation algorithm of resolver based on FPGA is studied to improve the resolution of position detection.In order to improve the sinusoidal degree of the two sinusoidal and cosine signals and restrain the influence of noise and dynamic offse t in the process of signal transmission,a FIR bandpass filter is designed,and the arc tangent value of the two signals is obtained by the algorithm of coordinate rotation digital calculation.In order to further improve the demodulation accuracy,the position tracking closed-loop is designed,and the influence of its parameters on the tracking performance is analyzed and discussed.Finally,the hardware experiment platform of low-speed permanent magnet synchronous motor based on the ARM control chip STM32F407 is designed.On the basis of analysis and simulation,the correctness of position demodulation algorithm and disturbance torque observer feedforward control method is verified by experiments.