Research On Direct Force Control Method Of Permanent Magnet Linear Synchronous Motor

Permanent magnet linear synchronous motor(PMLSM)adopts the strategy of converting energy into mechanical energy and eliminates physical deceleration and transmission components,such as screw,belt and chain.Because of its advantages of fast response,high precision and high power density,PMLSM is widely used in highprecision machine tools,industrial transmission,transportation and other fields.Fractional order calculus(FOC)has the characteristics of reducing static error,strong robustness,storing complex information and describing memory,and adopting fractional control can improve system performance in a certain range.In this paper,the direct force control(DFC)technology of PMLSM is further studied to improve the antiinterference ability of forcet and speed response of PMLSM.The main research contents and innovations are as follows:(1)The control methods of PMLSM are further classified and determined to be based on DFC technology.The mathematical models of PMLSM in different coordinate systems are established.The application of DFC technology in PMLSM is analyzed in detail,and the simulation model of traditional DFC technology in PMLSM is built in MATLAB/Simulink.(2)Given the factors such as forcet and flux jitter in PMLSM-DFC,the hysteresis comparator in forcet and flux is replaced,and the switch table selection module is replaced by SVPWM,which improves the forcet jitter caused by discontinuous switching of space vectors.Simulation results show that compared with traditional PMLSM-DFC,the forcet jitter of PMLSM-SVPWM-DFC is significantly reduced and the flux jitter is suppressed.As to the overshoot of speed response in the simulation results,the sliding mode control(SMC)technology is adopted in the speed loop regulator,which has achieved good results,and ensures a good premise for adopting FOC control technology in PMLSM.(3)The FOC theory is introduced into SMC,and a fractional sliding mode control(FOSMC)speed loop controller is designed,which can enhance the anti-disturbance ability of the system and reduce the static error.Given the slow speed response,low precision of speed loop,large fluctuation of flux linkage and forcet,and poor antidisturbance performance of traditional FOSMC in PMLSM-DFC,an improved FOSMC algorithm is designed for speed loop regulator.The algorithm adopts a combined reaching law of fractional double power exponential reaching law and fractional variable speed reaching law,which can effectively reduce system oscillation and accelerate reaching rate.Simulation results show that compared with traditional FOSMC,Adopting improved FOSMC in PMLSM-DFC,the fluctuation of flux linkage and forcet is weakened,the response speed of the system is accelerated,and the antiinterference ability of forcet response of PMLSM is improved.(4)The FOC theory is introduced into the sliding mode variable structure model reference adaptive system(SM-MRAS),and the observer of traditional fractional sliding mode variable structure model reference adaptive system(FOSM-MRAS)is designed,which can enhance the anti-disturbance ability of the system and reduce the static error.Given the traditional FOSM-MRAS with large speed estimation error,slow response speed,poor anti-interference ability and complicated calculation process under PMLSM-DFC,an improved FOSM-MRAS observer is designed.in the speed identification,the fractional adaptive law is simplified according to zero direct axis current,which reduces the calculation complexity and error calculation.The FOSMMRAS observer control law based on the fractional-order double power exponential reaching law is applied to the PMLSM-DFC system without speed sensor control.At the same time,the improved FOSMC speed controller replaces the PI speed controller,which improves the speed tracking performance and weakens the influence of motor parameter variation and system error on forcet,flux linkage and identification accuracy.The simulation model of PMLSM-DFC based on the improved FOSM-MRAS observer was built,and the control method was further realized.