Research On Predictive Current Control Of Permanent Magnet Synchronous Motor Based On Improved Sliding Mode Control

Permanent Magnet Synchronous Motor(PMSM)has the advantages of simple structure,high efficiency and low loss.It has become an important driving source of servo system and is widely used in various fields.Due to the existence of nonlinear disturbances such as external disturbances or changes in their own parameters during the operation of PMSM,the tracking accuracy is reduced and it is difficult to maintain the stable operation of the system.Therefore,it is of great theoretical and practical significance to study the optimal control strategy of PMSM.In this thesis,PMSM is taken as the research object.Based on the theory of sliding mode control algorithm and predictive control algorithm,an improved sliding mode control based on torque compensation and an improved deadbeat predictive current control algorithm are proposed.The control performance of PMSM is improved,the influence of internal and external disturbances on motor control performance is solved,and the chattering phenomenon in sliding mode control is weakened.The research contents of this thesis are as follows:(1)Based on the analysis of the structure of PMSM,the mathematical models of PMSM in different coordinate systems are deduced by Clark transform and Park transform,and the vector control based on coordinate transformation is expounded.The disturbance factors of PMSM control system are analyzed,which lays a foundation for subsequent simulation and experimental research.(2)The speed loop control algorithm of PMSM control system is improved.The sliding mode control theory is analyzed,the stability condition of sliding mode control is derived,and an improved sliding mode control algorithm based on torque compensation is proposed.The causes of chattering in sliding mode control are analyzed.The sliding function is introduced into the sliding mode reaching law,and the PID sliding mode surface is designed to improve the order of the sliding mode controller and weaken the chattering phenomenon.In order to solve the influence of external disturbance on the performance of the motor,the torque update law is derived to track the torque disturbance and improve the robustness of the system.(3)The current loop control algorithm of PMSM control system is improved.Based on the analysis of deadbeat predictive current control theory,the discrete mathematical model of PMSM is derived,and an improved deadbeat predictive current control is proposed.Aiming at the problems of parameter mismatch and one-beat delay in the traditional deadbeat predictive current control,the observation current obtained by the stator current disturbance observer is proposed to replace the sampling current in the deadbeat predictive control to compensate the influence of one-beat delay.The parameter disturbance observation value is used to compensate the voltage of the deadbeat predictive current controller to improve the stability of the current loop stator current.The simulation results in MATLAB/Simulink show that the improved sliding mode control algorithm can weaken the chattering and reduce the system error.The torque update law can track the load torque and improve the robustness of the system.The improved deadbeat predictive current control algorithm solves the problem of onebeat delay and parameter disturbance,and improves the stability and robustness of the system.The experimental results of AISim semi-physical simulation platform show that the proposed control algorithm can improve the performance of PMSM control system to a certain extent,and the experimental results are consistent with the simulation results.