Research On Thrust Compensation Control Technology Of Permanent Magnet Linear Synchronous Motor

The Permanent Magnet Linear Synchronous Motor (PMLSM) is changed by the rotating electric machine. Compared with the rotary motor, it has the advantages of high thrust, fast response, high accuracy and so on. But there are also shortcomings cannot be denied. On the one hand, due to the load directly applied to the linear motor with no intermediate drive mechanism, the change of the load transmitted directly to the linear motor making the thrust of the linear motor change. Linear motor thrust fluctuation may cause a resonance during low speed running, which deteriorate the control effect. On the other hand, the structure of linear motor can be identified as an expansion along the section of the rotary motor. Therefore, its own existence end effect and the cogging effect of the linear motor makes the thrust fluctuate. This article will show the thrust fluctuation compensation of PMLSM from two different angles.Firstly, this article introduces the basic structure and operation principle of the permanent magnet linear synchronous motor, the vector control and the SVPWM control principle, analyzes its mathematical model, and establishes the PMLSM control simulation model in MATLAB/SIMULINK. Secondly, in this article, the thrust fluctuation of PMLSM is compensated and inhibited from the angle of control and the improvement of structure.From the angle of the control, this article adopts the method of CMAC and the PID compound control, which makes the thrust under the control by tracking the current of PMLSM. Compared with using PID control only, and CMAC control only, it validated the superiority of the compound control. From the angle of changing its structure, this article adopts the method of finite element analysis to analyze the factors that cause the thrust fluctuation of PMLSM, which inhibits the thrust fluctuation from the way of inhibiting the cogging force fluctuation. A PMLSM model and simulation are established in the ANSOFT finite element analysis software. Then, the change of cogging force with different magnetic poles are analyzed, and the static magnetic field and the transient magnetic field under running condition are observed.The result of the simulation shows that, the CMAC-PID compound control enhanced the stability of the system, which restrained the disturbance of the system and greatly reduced the overshoot, and speeded up the control response speed. Besides, the finite element analysis results showed that, setting the polar distance about 1.5 times of tooth pitch could reduce the size of the cogging force and weaken the cogging effect of thrust under the basic structure of the motor does not change. The method had achieved the effect of suppressing cogging and improved the stability of the motor system.