Electromagnetic Design And Performance Analysis Of Permanent Magnet Brushless DC Linear Motor

Permanent magnet brushless DC linear motor is a new type of permanent magnet linear motor.Compared with the traditional “rotary motor with ball screw” transmission mode,the direct-drive mode not only reduces all kinds of negative effect of the mechanical transmission but also has advantages such as simplified structure,high efficiency,fast response,easy control and so on.Therefore it is getting more and more attention.In this thesis,it is applied to the driving gear used for pushing the object do reciprocating linear motion in the machine tool.So a kind of tubular permanent magnet brushless DC linear motor is designed.Taking it as the research object,the operating principle,structure size and working performance of the motor are analyzed.This thesis mainly focuses on the design and performance analysis of tubular permanent magnet brushless DC linear motor,including the following several aspects:Firstly,the structural characteristics and working principle of the tubular permanent magnet brushless DC linear motor are introduced in detail.According to the structural characteristics of the tubular permanent magnet brushless DC linear motor,the com-mutation process of the motor is analyzed.The mathematical model of the motor and the expression of three-phase current in the commutation process are derived analytically.Secondly,the magnetic circuit method and finite element method are combined to calculate the magnetic circuit of the motor for determining the size of each part of the tubular permanent magnet brushless DC linear motor and verifying its rationality.Using finite element analysis software,two-dimensional finite element model is established to analyze the electromagnetic performance of permanent magnet brushless DC linear motor.Finally,the detent force which affects the performance of the tubular permanent magnet brushless DC linear motor is studied.The analytical expressions of cogging force and end force of the tubular permanent magnet brushless DC linear motor are derived respectively and the methods to restrict the detent force are gived.The influence of electromagnetic performance of the tubular permanent magnet brushless DC linear motor are analyzed from the length of air gap,size of primary core structure and permanent magnet and the shape of magnetic conductor.The research and analysis in this thesis can provide some theoretical guidance for the future design of tubular permanent magnet brushless DC linear motor.