Optimal Design Of Magnetic-geared Flat Linear Machine

The wide application of permanent magnet linear motors reflects the variable and simple advantages of the motor’s own structure.However,with the popularization of high-speed logistics,cordless elevator and other new fields of application,the limitations of motor manufacturing technology and design and processing have caused the cost of system manufacturing materials to increase sharply,and the workload of system maintenance cannot be ignored.The Magnetic-Geared Flat Linear Machine(MGFLM)that solves these drawbacks has severely restricted the application of the motor in the long-stroke linear traction system due to its lower power factor.This paper carries out research work on the optimization design of MGFLM,in order to improve the power factor of the motor.The main contents are as follows:Firstly,starting from the working principle of the linear magnetic field modulated motor,the analytical equations of air gap flux density,power factor and average thrust are derived,and the influence of variables on the basic physical quantity of the motor is sorted out.The distribution of permanent magnet,poles pairs of permanent magnet,the equivalent pole-pairs of armature windings,width of tooth shoe,structure of modulator blocks and current excitation initial phase angle are determined as the main variables affecting thrust characteristics and power factor.Secondly,the terminal voltage waveform data obtained by using Ansys Maxwell software simulation is applied to the analytical calculation to obtain the input voltage waveform.The FFT method is used to decompose the input voltage and current of the motor,and the cosine value of the fundamental phase angle difference is calculated,and then the power factor value is obtained.Then,the influence of structural variables on thrust characteristics and power factor of MGFLM is studied.Compared with the Normally magnetized MGFLM,the MGFLM with Halbach permanent magnet array has a 2.74% increase in the content of the air-gap magnetic density fundamental wave,a general decrease in the content of various harmonics,and the power factor is also increased from 0.497 to 0.649.With a more suitable magnetic pole combination,the power factor can reach 0.762,but the average thrust is reduced by 14.3%.In addition,compared to the three shapes of rectangular,elliptical and trapezoidal modulator block,the trapezoidmodulator block has the best magnetization effect,followed by the rectangle.Analyse the rectangular modulator block with curved edges on the left and right sides.Under the shape of convex on the left side and concave on the right side,magnetic lines of force are more distributed in the modulator blocks.At this time,the power factor and average thrust are both large,and the thrust fluctuation is almost unchanged.Finally,to study the correlation between variables,the sensitivity analysis of structural variables is carried out,and the proportion of each sensitive factor is obtained.Among them,the permanent magnet ratio and the left radius of modulator block have a greater impact on the power factor,while the length of the upper side of the modulator block and the width of tooth shoe have a greater impact on the average thrust.Taking the power factor as the objective function and the average thrust as the boundary condition,the Pareto frontier is obtained by optimizing the NSGA Ⅱalgorithm.At the same time,the Box-Behnken optimization method in another Design Expert experimental Design and analysis software was applied to analyze.Comparing the final optimization schemes obtained by the two methods,it is concluded that the average thrust of the NSGA Ⅱ optimization scheme is 415.9N,which is 4.2% lower than the average thrust of Normally magnetized Magnetic-Geared Flat Linear Machine.The Box-Behnken optimization scheme has an average thrust of 410.4N,reduced by 4.2%.The power factor of the two schemes is not much different,both are about 0.72,which is an increase of 45.1% and 44.9%respectively.Combined with the characteristics of the motor’s forward and reverse rotation,the Box-Behnken optimization scheme with a smaller difference in average thrust between forward and reverse rotation was selected as the final scheme.The optimization design research done in this paper provides a complete set of process reference for the design and optimization of Magnetic-Geared Flat Linear Machine,and provides a new idea for the optimization of the power factor of the motor,which is of great significance to the research on the improvement of the power factor of the magnetic field modulated motor for long stroke.