Optimal Design Of Thrust Characteristic Of Flat Permanent Magnent Linear Synchronous Motor

The flat permanent magnet linear synchronous motor(PMLSM),as a typical of modern direct-drive linear servo motor,has many advantages,such as high thrust density,high positioning accuracy,sensitive response,fast acceleration.These advantages mentioned above make PMLSM has a wide application.However,the large thrust ripple produced in PMLSM,which severely affects the servo performance of the PMLSM and needs to be effectively suppressed.In order to suppress the thrust ripple and improve the average thrust,dimensions optimizations of the PMLSM are performed.The main works of this paper are as follow:Firstly,the influences of dimensions or special structure of the PMLSM on average thrust and thrust ripple are studied.Through the finite element parametric analysis,the length of the primary core has a great influence on the thrust ripple,and the maximum difference can be 155 N.For the PMLSM with arc-shaped auxiliary pole,the position of the arc-shaped auxiliary pole has the greatest affect on the thrust ripple,followed by the arc radius.After optimization of the position,height,radius and theta,the average thrust can keep unchanged and the thrust ripple can be reduced by 66.4%.In the two-sectional primary PMLSM,with the primary phase differs by half a pole distance and winding reorganization,the average thrust can be doubled and the second harmonic in the thrust ripple can be eliminated effectively.In addition,the end slot of the PMLSM is half-filled,reasonable design of unequal slot width and magnetic pole dimensions optimization can improve the thrust characteristics of PMLSM.Secondly,the sensitivity analysis of the dimensions of the arc-shaped auxiliary pole PMLSM was carried out.the Taguchi method is used to deign an orthogonal table of twelve design parameters,which is divided into two groups.And the signal-to-noise ratio analysis were performed on the thrust ripple and average thrust respectively.Six sensitive variables are selected,including the position and height of the arc-shaped auxiliary pole,the width and height of the magnetic pole,the width of the notch and the slot.Then,the kriging surrogate model assisted multi-objective particle swarm optimization is used to realize the optimal design of PMLSM.Six sensitive variables are determined as the optimization variables,and the thrust ripple and average thrust of PMLSM are taken as the objective functions.The kriging surrogate model is used to model the objective functions with high precision by using the improved latin hypercube experiment design and the expected improvement add-point criterion.Combined with the multi-objective particle swarm optimization algorithm,the Pareto frontier of two objective function solutions is obtained.After optimization,the thrust ripple of PMLSM is reduced by 64% and the average thrust is increased by 6.6%.With the skew pole,the thrust ripple can be reduced to 92% and the average thrust can be increased by 2%.Finally,the test methods of the force characteristics of PMLSM are studied,and a test platform of handwheel and ball screw and rotary servo motor is designed.The prototype and test platform of the PMLSM are performed.Through the above study work,a multi-variable and multi-objective optimization design method is proposed.The optimization design method is also applicable to other types of motors and provides a theoretical basis for the optimization design of other motors.