【作者】 张玉秋；

【导师】 叶云岳；

【作者基本信息】 浙江大学 ， 电气工程， 2013， 博士

【摘要】 永磁直线伺服电机(PMLSM)具有结构简单,运行可靠,体积小,质量轻,推力密度大,效率高,可控性好,运行平稳等优点,已逐渐成为直线伺服系统的主流驱动电机,而如何提高推力密度和削弱推力波动一直是永磁直线伺服电机领域的两个重要研究内容。本文围绕这两个问题,对两种常用结构的永磁直线伺服电机进行了深入研究,分别为适用于轻载、快速反应、高精度特性要求场合的双边空心PMLSM (DAPMLSM)和高负载、大推力要求场合的单边水冷PMLSM。首先基于等效磁化强度法建立了PMLSM磁场分布和推力特性解析计算的统一分层线性模型,适用于不同形状及分布的永磁体、不同交直流电枢电流及不同绕组分布的PMLSM。其次对DAPMLSM进行了电磁设计。推导了空载气隙磁场解析表达式,对其他磁体形状的DAPMLSM提出了将磁体分成矩形块再线性叠加的简化统一的处理方法,并给出了电机各参数的选取原则。指出优化空载磁通密度波形可有效降低推力波动,提高伺服性能。另外,该类电机横向边缘效应较大,会影响气隙磁场分布、使空载反电势和推力幅值减小,因此定义了横向漏磁系数做定量衡量,其主要影响因素为电机横向长度、气隙高度和永磁体厚度。实验样机的测量结果验证了解析模型和有限元分析的可信性。再次,针对单边水冷PMLSM首先对其进行了电磁设计,研究了铁心端部磁场的分布特点；综合运用多种措施有效降低了磁阻力。在建立的直线电机对拖平台上测量了样机的空载与负载往复运动特性,证明了样机具有较好的伺服性能。最后,重点分析了其热特性并设计了合理的水冷系统,大幅度提高了电磁负荷与推力密度。在损耗计算的基础上,建立了三维温度管流耦合场模型,运算速度快,且可综合考虑修正热源、接触热阻、初次级间热传递、水流流动和冷却等方面对电机温度分布的影响。研究了无水冷和有水冷时不同工况下的热特性,得出最大允许负载电流和最大工作时间,为电机驱动提供指导。总结了PMLSM水冷系统参数和水道的设计原则。附加水冷系统后,在同样的温升限值下,长时间运行的最大推力密度提高为无水冷时的2.6倍,大大提高了驱动能力。在直线伺服系统中添加了空气绝缘隔离和精确水冷系统,降低了工作平台温度,减少了机床部件的热变形,从而保证了伺服加工精度。实验测量结果与温度分析模型计算结果相符,验证了温度分析方法和分析结论的正确性。更多还原

【Abstract】 Permanent magnet linear servo motor (PMLSM) has the advantages of simple structure, small size, light weight, high thrust density, high efficiency, good controllability and stable and reliable operation. Thus it has gradually become the mainstream of the linear servo motor. However, how to improve the thrust density and weaken the thrust ripple have been two important contents in the research field of PMLSM. The studies of two commonly used PMLSM structures are carried out about the two issues in this paper. One is double-side air-cored PMLSM (DAPMLSM) which is suitable for light loads, rapid response, high precision requirements, and another is unilateral water-cooled PMLSM which is suitable for high-load, high-thrust occasions.Firstly, based on the equivalent magnetization intensity (EMI) method, the unified hierarchical linear model is established for PMLSM magnetic field and thrust analytical calculation. It is suitable for permanent magnet with different shapes and distribution, different AC or DC armature currents and different winding distributions.Secondly, the electromagnetic design of DAPMLSM is studied. Analytical expression of no-load air-gap magnetic field is obtained based on EMI. One simplified and unified method for other shapes PM is introduced, through dividing PM to rectangular segments and then superposing. The selection principles of motor parameters are given after analysis. Intelligent algorithm is introduced to optimize the no-load flux density waveform, effectively reducing the thrust fluctuations and improving the servo performance. The larger transverse end-effect of DAPMLSM will affect the air-gap magnetic field, no-load back EMF and thrust. Thus a flux leakage coffeient is defined to evaluate the end-effect, and it is influenced by the transverse length of the motor, the height of the air-gap and the height of. PM Experiments of the prototype verify the credibility of the analytical model and finite element analysis.Thirdly, the electromagnetic design of unilateral water-cooled PMLSM is studied. The magnetic field distribution characteristic at the end of the primary is obtained. The detent force is reduced through comprehensive use of various methods after the source analysis. Based on the established linear motors platform, reciprocating motion characteristics under no-load and load conditions are measured. The results indicate the motor has good servo performance.The final studies mainly focus on its thermal characteristics and reasonable cooling system design to improve its electromagnetic load and thrust density. Based on the loss calculation results, a three-dimensional model coupling temperature field and pipe flow is established. It calculates fast and could comprehensive consider the heat source modification, the thermal contact resistances, heat transfer between the primary and the secondary, water flow and its cooling effect on the temperature distribution in the motor. The thermal characteristics of the usual and the water-cooled motor in different conditions are studied. The obtianed maximum permissible load current and the maximum operating time provide guidance for the motor drive. The parameters selection methods and the design principles of the water-cooling system are provided for the guidance of PMLSM water-cooling system design. Because for the additional water-cooling system, the maximum thrust density is improved2.6times with the same temperature rise limits. It indicates the drive ability of PMLSM is greatly improved. Air-insulated isolation and precise cooling system are added to the linear servo system to reduce the temperature of the working platform, reduce the thermal deformation of machine components and to ensure the servo machining accuracy. The experimental results and temperature analysis match well, verfiying the correctness of temperature analytical methods and conclusions.更多还原