Analysis And Suppression Of The Detent Force Of Double-secondary Permanent Magnet Synchronous Linear Motor

Permanent magnet synchronous linear motor(PMSLM), especially PMSLM with double-secondary has a lot of advantages including high speed, high accuracy, large thrust and zero-normal force and so on, which is applied to servo system of ultra-precision machine tool widely. It promotes the development of manufacturing technology and attaches great attention by many specialists and scholars at home and abroad. However, detent force (DF) caused by cogging effect and end effect is the main influence of ultra-precision machine tool positional accuracy and kinematic accuracy. The existence of DF constraints the development of PMSLM. Therefore, this paper analyzes detent force and studies DF suppression method which starts from double-secondary PMSLM ontology structure. The main contents of this paper are as followed:Firstly, the basic structure and operating principle of PMSLM is analyzed briefly. We achieve the analytical expression of PMSLM detent force by the combination of magnet circuit method and energy method. Meanwhile, finite element method (FEM) is adopted to set up the FEM model of double-secondary PMSLM. Total harmonic distortion (THD) is introduced to quantitatively analyze the influences of DF amplitude and spatial harmonic which caused by changing five structure parameters. Rate of parameter change is also introduced to analyze the effects at the same time. We validate the accuracy of FEM model through comparing analytical results and FEM results.Secondly, two steps are adopted to suppress DF of double-secondary PMSLM. The first step is orthogonal experiment design, and initial suppression results are obtained by orthogonal experiment schedule table and variance analysis. It is proved that both DF amplitude and THD of the motor after suppressed are decreased to some degree. Magnets-staggered method is put to use to repress DF further in the second step. Influences of different pole stagger distances on PMSLM thrust and the performance of DF are analyzed. The minimum ratio between DF amplitude and average thrust is chosen as a standard to determine the best pole stagger distance. FEM modeling results show that the double-secondary PMSLM DF suppression method is feasible.Finally, two common DF test methods are analyzed and compared. According to existing method and characteristics of double-secondary PMSLM, we start from the high-demanding of ultra-precision machine tool to design DF test equipment. The aim is to complete sample DF testing.