Detent force suppression of permanent magnet linear synchronous motor based on a V‐shaped tooth‐slot structure

Abstract

Given the existence of detent force, the positioning accuracy of permanent magnet linear synchronous motor (PMLSM) with an iron core worsens in its application in the field of the precision drive. To address this problem, a method is proposed to weaken the detent force of PMLSM with a V-shaped tooth-slot structure. The models of the detent force, including the cogging force and end force, are established theoretically. The analytical expressions of cogging force and end force are obtained by analysing the ripple rule of the motor. Then, the tooth-slot surface of the motor with the V-shaped tooth-slot structure conducts infinitesimal processing. The relationship between cogging force, end force, and the V-shaped depth of the V-shaped tooth-slot PMLSM is deduced, respectively, using the integration method. Furthermore, Ansoft finite element simulation software Maxwell module is used to compare the conventional PMLSM, V-shaped magnetic pole PMLSM, and V-shaped tooth-slot PMLSM. The comparison reveals that the V-shaped tooth-slot structure has the excellent characteristic of increasing the average value of thrust while reducing the ripple of thrust caused by detent force. Finally, prototype fabrication and experiments are conducted to verify the correctness and feasibility of the proposed method. K E Y W O R D SAC motors, design, electric machine analysis computing | INTRODUCTIONCompared with conventional rotary motors, a permanent magnet linear synchronous motor (PMLSM) can drive the load directly without a ball screw. It more easily achieves high thrust density, high positioning accuracy, fast acceleration, low noise, and so on. Thus, PMLSM is widely used in numerical control machine tools, electromagnetic ejection, cordless elevators, rail transportation, and other fields [1][2][3][4].However, given the end force brought by the disconnection of the end and the cogging force in the motor's own tooth-slot structure, PMLSM generates large detent forces during operation, which affects its operating efficiency. Hence, the methods to weaken the detent force of the linear motor must be explored to improve the operating efficiency of PMLSM and ensure the stability of the linear motor during the operation.At present, the generation and weakening principle of the detent force have been extensively researched and reported. The research on the weakening of detent force mainly includes two aspects: the optimisation of the motor structure and the improvement of the control strategy. The technology to minimise the detent force of PMLSM is shown in the tree diagram in Figure 1. From the point of view of the control strategy, the authors in Ref. [5][6][7] apply compensation control with the compensation windings to reduce the thrust and velocity ripple. The study in Ref. [8] focuses on the current control with a supertwisting algorithm to weaken the detent force. From the perspective of the motor structure, methods for weakening detent force can be mainly divided into threeThis is an open access article under the terms of the Crea...