磁极组合式永磁丝杠的结构分析与优化

STRUCTURE ANALYSIS AND OPTIMIZATION OF MAGNETIC POLE COMBINED PERMANENT MAGNETIC SCREW

为改善永磁丝杠复杂的螺旋形磁极加工制造难度,对螺旋磁极结构进行改进替代。应用有限元法(Finite Element Method,FEM)对推力和转矩静特性进行仿真,证明丝杠磁极为斜环、螺母磁极为螺旋结构和丝杠磁极为螺旋结构、螺母磁极为斜环的两种永磁丝杠结构能够实现平稳传动。由于结构中仍部分存在螺旋结构,故进行实用化改进。方案一是将直环离散的若干圆弧形磁极块阶梯式组合排列;方案二是采用半斜环磁极组合结构。结果表明,后者组合磁极块数更少,在保证运动系统平稳传动的同时,具有更大的推力和转矩。同双螺旋永磁丝杠相比,推力误差和转矩误差仅分别为3.981%和0.583%,故而为替代螺旋磁极的一种较为理想的方案。此外,提出了极距比K的概念,得出K=0.3时,单位磁极产生的电磁推力和转矩最大,磁极利用率最高。在此基础上,将半斜环磁极结构采用Halbach阵列优化,峰值推力和转矩可分别提升42.3%和36.3%,且存在最优辅配比λ=0.4。

In order to improve the manufacturing difficulty of the complex helical⁃shape magnetic pole(HSMP)in permanent magnetic screw,the structure of HSMP is improved and replaced.The static characteristics of thrust and torque were simulated with the finite element method(FEM).It is proved that the two kinds of permanent magnetic screws,whose screw is oblique ring magnetic poles(ORMP),nut is HSMP,and screw is HSMP,nut is ORMP,can realize smooth transmission.Two practical improvements were carried out,because there were still some HSMP in the structures.Scheme one was to combine and arrange several circular arc⁃shaped magnetic poles(CASMP)blocks in step.Scheme two was a semi⁃oblique ring magnetic poles(SORMP)composite structure.The results show that the number of combined pole blocks required for the latter is less,it can ensure the smooth transmission of the motion system,at the same time,with greater thrust and torque.Compared with LRMG which screw and nut are HSMP,the thrust and torque errors are 3.981%and 0.583%respectively,so it is an ideal scheme to replace HSMP.In addition,the concept of pole pitch ratio K was proposed,and it is concluded that when K=0.3,the thrust and torque of unit volume pole have the largest value,and the utilization rate of magnetic pole is the highest.On this basis,SORMP composite structure is optimized by Halbach array.The peak thrust and torque can be increased by 42.3%and 36.3%respectively,and the optimal auxiliary ratioλ=0.4.