Research On Predictive Current Control Strategy Of Permanent Magnet Synchronous Linear Motor

As the core unit of the direct drive transmission mechanism,the permanent magnet synchronous linear motor has the advantages of large thrust density,high control accuracy,and small mechanical loss.It is widely used in semiconductor manufacturing equipment,computer numerical control lathes,lithography machines and other high-precision equipment.In the vector control system of PMSLM,the quality of the current loop determines the control performance of the entire motor system.Compared with the traditional current control algorithm,the predictive current control algorithm has good dynamic performance and static performance,and is more suitable for some high-precision occasions,which has been widely concerned by a large number of scholars.However,predictive current control of PMSLM is a model-based control algorithm.In actual operation,changes of parameters in the motor model seriously affect the motor control performance,causing current static errors or even oscillations.Therefore,the research on predictive current control strategy is carried out which takes PMSM as the research object.It is of great significance to solve the above problem.Based on the analysis and review of PMSLM and its control strategies,the basic structure and working principle of the permanent magnet synchronous linear motor are introduced,and its mathematical models in the three-phase stationary coordinate system,the two-phase stationary coordinate system,and the two-phase rotating coordinate system are established according to the coordinate transformation related theory.The basic idea of vector control is also expounded.The discrete mathematical model of the PMSLM is derived and the PWM predictive current control model of the permanent magnet synchronous linear motor is constructed on the basis.The delay caused by the digital control system is compensated through calculating the reference voltage command of the next cycle.The steady-state current error and current oscillation caused by the change of motor parameters are analyzed.In order to solve the problem of parameter disturbance,an incremental predictive current control model was derived based on the PWM predictive current control,thereby designing a robust predictive current controller without the flux parameters which eliminates the impact of flux parameter disturbance to the controller performance.Theoretical analysis on the parameter sensitivity of the robust predictive current controller is also performed.Aiming at the current error caused by the mismatch of the inductance parameters,the robust predictive current controller is improved.A new sliding mode observer based on exponential approach is designed,and the observed voltage disturbance value is feed forward compensated.The stability of the sliding mode observer is analyzed by constructing Lyapunov function.Finally,the predictive current control simulation model of PMSLM proposed in the paper is built in Matlab/Simulink.The simulation of traditional PWM predictive current control algorithm and the robust predictive current control algorithm before and after improving are compared and tested.Simulation results show that the improved robust predictive current control algorithm has better resistance to load disturbances and parameter robustness than the traditional PWM predictive current control algorithm.So as to verify the correctness and effectiveness of the proposed algorithm further,an experimental platform for permanent magnet synchronous linear motors based on dSPACE is established.The experimental platform is used to verify the proposed algorithm,and the experimental results are found to be consistent with the simulation results.