Optimal Design On Reducing The Normal Force Ripple For Pmlsm

Linear motor has the merits of high precision, fast speed and long travel, it can achieve'Direct-driving'in the servo systems of CNC machine tool. Compared to other types of linear motor, permanent magnet linear synchronous motor as a servo motor has a great advantage, but the normal force ripple, especially in the servo feeding system of high-speed high-precision machine tool, will lead feeding table vibration or resonance with other moving components of the servo feeding system, it will affect the performance of the servo system. For the problem of normal force ripple, this thesis will research on the optimal design to deal with this problem.The structure and windings of PMLSM were introduced, and the principle of electromagnetic design of PMLSM was summarized.The formulas of flux density of air-gap, thrust and normal force of PMLSM was deduced, and the results prove that decent force is the primary aspect that affecting the normal force ripple. Different component of decent force for was analyzed for further optimal design.The optimal design of skew or V-skew PM was adopted for secondary. The analysis of Fourier regression and limited enumeration method were used to calculate the optimal parameters for optimal design of primary. Combine with all of result of optima to fix on the final optimal projection.Base on the theory of phase-offset of unit motor, aim to the characteristic of harmonic component of unit motor, the method that to make each of unit motor to offset particular angle for counteract main harmonic component of electromagnetic force was adopted. The parameter of original motor was modified, and some particular teeth was lengthened by high permeability material to achieve this projection.The optimal design of Halbach PM array for the secondary of PMLSM was adopted, each pair of pole was composed by six discrete PM units for the flux density of air-gap can approach to sine. Base on this optimal design, the harmonic of flux density of was decreased, and the normal force ripple was reduced.