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The ripple normal force of permanent magnet linear synchronous motor (PMLSM) can directly deteriorate the machining accuracy of ultra-precision CNC machine tool which use linear motor direct drive. First, the normal force of PMLSM was calculated using finite element method (FEM) .then, id current compensate lookup table was established by indexing iq current, gap and position of mover .In order to reduce the ripple of normal force and keep the thrust steady, PMLSM current compensation control system was realized by injecting the id current to counteract the normal force ripples using field oriented control (FOC) method. The effectiveness of this proposed method is verified by the simulation using Matlab according to the comparison between the compensation and no compensation cases.

With the development of industry and technology, the need for freshwater increases day by day, the contradiction between the fresh water for production and livelihood is sharpened. An important way to solve the problem is desalinization of the groundwater. In this paper reverse osmosis disposal process of groundwater are used, PLC are used to control electromagnetic valves and water pumps in the desalinization water treatment system and automatic switching state or stop. Using touching screen as man-machine interface, which is more convenient for the operator to know the working stages, and is more facility for desalinization process. The system has many advantages, such a saving energy, high efficiency, more safety, control modes flexible and various, function extension easily. It has great significance in reduce cost of desalinization of groundwater and remission serious lack of the freshwater in some areas of China.

Permanent Magnet linear synchronous motor (PMLSM) exist the problem of normal force fluctuation, especially in the servo feeding system of high-precision CNC machine tools. The normal force fluctuation can cause the feeding table in vibration and produce resonance with other moving components of the servo feeding system. It is produced by normal electromagnetic force wave acting on iron cores of PMLSM. In this paper, the analytical expression of normal electromagnetic force wave of single-side PMLSM is deduced with the method of MMF (magnetomotive force) magnetic permeance. And based on this, analyze composition and classification of the force wave component; the further study of the influences to the force wave order and amplitude when the coefficients of the electric machine are changed is done. Then, base on a PMLSM with 6 poles and 36 slots, the results of analytic calculation are accordant with the FEM simulation ones. These results prove the analytical expression is correct and accurate.

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