Analysis And Restraint Of The Thrust Fluctuation Of Permanent Magnet Synchronous Linear Motor

The application of linear motor has become more prevalent in the motor system than ever before, but the thrust fluctuation which exists in the linear motor affects the operation efficiency of the linear motor, so it is very necessary to analyze and restrain the thrust fluctuation. This paper takes the Permanent Magnet Synchronous Linear Motor (PMSLM) as the research objective, and focuses on the thrust fluctuation of PMSLM and also analyzes and studies the compensation measure by means of Fuzzy Analytic Hierarchy Process (FAHP).Firstly, this paper introduces the general structure and basic principle, and establishes the analytical model and the finite element model of the PMSLM to analyze the magnet field and the electromagnetic force. According to the analysis of the operation principle, the character of electromagnetic force and the thrust fluctuation of PMSLM, this paper points out the effect of horizontal thrust on motor performance and presents the main reasons of thrust fluctuation of PMSLM in details: the on-off of armature core and edge effect caused by the discontinuity of stator winding edge arrange; the ripple undulation caused by the non-sine of primary current and primary opposite electromotive force; the ripple undulation caused by the property of magnetic steel and the influence of its distribution; the cogging effect caused by the air-gap permeance between the stator and the active cell.Secondly, based on the theories about the thrust fluctuation, the restraining measure related to specific effect elements are listed in details. Because of the kinds of elements which are connected with and influenced on each other, this paper gets the weight of each element by the means of Fuzzy Analytic Hierarchy Process, and on the basis of the analyzing results, gives out the indemnifying measure especially: such as improving the efficiency of the magnetic steel, optimizing the magnetic field and the counter-electromotive force, increasing the width of slot and changing the length of active cell to decrease the cogging effect, etc.Lastly, after optimizing the structure and the magnetic circuit of the motor, magnetic field and the wave of the primary opposite electromotive force and thrust fluctuation are measured in experiment. The experimental results show that these methods are valid and feasible, and the aims of decreasing thrust fluctuation is reached and the good performance is achieved.