Research On Speed Control Of Permanent Magnet Synchronous Motor Based On Improved Super-twisting Algorithm

Permanent-Magnet Synchronous Motor(PMSM)has many advantages,such as high efficiency,high reliability,low loss,low maintenance cost,so it is used in industry and manufacturing.However,due to the multivariable and strong coupling nonlinear characteristics of the motor,the output torque fluctuates greatly and the response time is long.Therefore,it is necessary to optimize and improve the motor control strategy to improve the control performance.Among many control strategies,sliding mode control is widely used in PMSM control because of its strong robustness,simple implementation and it can overcome system uncertainty.However,because of the vibration,the high frequency oscillation is produced in the controlled system.The nonlinear second-order sliding mode control can transfer the discontinuous switching term in the first-order sliding mode to the higher-order differential,thus effectively weakening the vibration.The second-order sliding mode control is applied to the design of speed controller of PMSM,which can make the permanent-magnet synchronous motor run more smoothly,reduce vibration,and have stronger ability of resisting external interference.The second-order sliding mode can also be applied to sensorless control of motor.At present,some permanent magnet synchronous motors still adopt the method of adding mechanical sensors to detect the rotor position and speed of the motor.This method not only increases the volume and cost of the motor,but also limits the application range of the motor.The sliding mode observer based on the second-order sliding mode principle not only liberates the constraints of the sensor to the development of the motor,but also has higher measurement accuracy than the traditional sliding mode observer.Combined with the development status and practical application of permanent-magnet synchronous motor,the following research scheme is proposed.Firstly,building the mathematical model of PMSM based on the principle of Field-Oriented Control(FOC),and the theoretical basis of Space Vector Pulse Width Modulation(SVPWM)technology and its waveform generation mechanism are described.According to the basic principle of sliding mode variable structure control,the design method of sliding mode speed controller is described in detail.Secondly,the finite time convergence mechanism of fast terminal sliding mode and convergence principle of super twisting algorithm around origin are explained respectively.Finally,the second-order fast sliding mode speed loop controller is designed by combining the fast terminal sliding mode with the super twisting algorithm,and the sign function is improved to a variable exponential quasi sliding mode function,through simulation,the speed and torque curves are compared to select the optimal parameters.It is concluded that the second-order fast sliding mode speed loop controller can effectively improve the rapidity and robustness of the system and weaken the vibration.Finally,after elaborating the principle and design method of sliding mode observer,the first-order sliding mode control law of the original sliding mode observer is replaced by the improved super-twisting algorithm with on-line adaptive adjustment,and the double filter structure is used to weaken the backward transmission of vibration.The simulation results are compared with the traditional sliding mode observer,which shows that the improved super twisting sliding mode observer can weaken vibration and improve the accuracy of rotor position and speed estimation.