Analysis of the Normal Force Ripple for the Flat Plate Permanent Magnet Linear Synchronous Motor

There is large normal force ripple between the mover and the stator when the single-side flat-plate permanent magnet linear servo motor (FP-PMLSM) is operating, and the friction force perturbation and the vibration of the machine tool caused by the normal force ripple will influence the accuracy of machine tools greatly. This article derives an analytical expression for the normal force of the FPPMLSM, revealing the influence of cogging effect, end effect, and armature reaction on the normal force ripple. The analysis results indicate that optimizing the parameters of the tooth slot and the primary end iron core can effectively suppress normal force ripple.

I. Introduction

Single-sided flat-plate permanent magnet synchronous linear motors (FP-PMLSM) have the advantages of high thrust density, high speed, high acceleration, high dynamic response, etc., and are widely used in advanced CNC machine tools, photoetching machines and other precision equipment [1–2]. In single-sided FP-PMLSM, not only is there a fluctuating horizontal thrust, but there is also a normal suction force between the primary and secondary of the motor that is an order of magnitude greater than the thrust [3]. During motor motion, the normal force fluctuates periodically due to cogging effect, end effect, and armature reaction. When PMLSM are used as the core feeding parts of precision equipment, the fluctuation of motor normal force will cause friction perturbation, which restricts the further improvement of precision equipment machining accuracy [4].