Investigation of synchronous reluctance motors for feed drives in machine tools

如今，用于进给驱动和辅助驱动（如机床行业的自动换刀装置）的最广泛使用的电机类型是高性能永磁同步电机（PMSM）。然而，这种永磁体的生产，基本上由关键的稀土元素组成，是非常昂贵和不生态的。由于原材料价格波动以及价格和质量方面的全球竞争，对机床部件的成本效益和生态可持续解决方案的需求正在增加。永磁同步电机的一种可能的替代方案是所谓的同步磁阻电机（SynRM），由于其没有永磁体，在过去几年中变得越来越有吸引力。通过优化转子的几何形状，以前已知的缺点，如扭矩涟漪和噪音已经显着减少。市场上的商用SynRM显示出低于2%的扭矩涟漪。由于结构坚固，即使在部分负载下也具有高能效，SynRM现在部分用于泵和风扇应用，以取代传统的三相交流电机。本研究项目将调查SynRM是否以及在何种程度上可以用作机床进给轴和辅助轴的驱动电机。除其他事项外，目的是调查控制算法的潜力，以改善转矩涟漪，并比较分析不同类型的电机的机器轴的动态行为。类似于PMSM，SynRM的速度可以很容易地控制与变频器。对进给驱动轴的初步仿真研究表明，SynRM可以应用于经济高效的进给轴。在本研究项目中，需要研究和进一步开发不同的控制技术来优化SynRM的性能。其基础是足够精确的电机模型，该模型描述了电流和转子角相关的电机特性。应通过各种负载曲线在电机试验台上确定必要的参数。主要目标是开发一种具有高带宽和低转矩涟漪的系统。为此，将研究嵌套控制回路的非线性控制器和Luenberger观测器。将建立一个带有实时控制系统的轴测试台，用于验证目的。这使得开发的方法进行测试，并允许不同的电机类型的比较调查。

Today, the most widely used electrical machine type for feed drives and auxiliary drives, such as automatic tool changer in machine tool sector is the high-performance permanent magnet synchronous motor (PMSM). However, the production of such permanent magnets, which essentially consist of critical rare earth elements, is very expensive and unecological. Because of the price fluctuations of raw materials and the global competition in terms of price and quality, the demand for cost-effective and ecologically sustainable solutions for machine tool components is increasing. One possible alternative to permanent magnet synchronous motors is the so called synchronous reluctance motor (SynRM), which has become more and more attractive in the last few years due to its absence of permanent magnets. By optimizing the rotor geometries, the previously known disadvantages such as torque ripple and acoustic noise have already been significantly reduced. Commercial SynRM on the market shows a torque ripple under two percent. Due to the robust construction and the high energy-efficiency even under partial load, SynRM are now partly used in pump and fan applications to replace the conventional three-phase AC motors. This research project will investigate whether and to which extent the SynRM can be used as drive motors for feed axes and auxiliary axes in machine tools. Among other things, the aim is to investigate the potential of control algorithms to improve the torque ripple and to comparatively analyze the dynamic behaviors of machine axes with different types of motors.Similar to PMSM, the speed of a SynRM can easily be controlled with frequency inverters. The preliminary simulation study of a feed drive axis shows that SynRM can be applied in cost-effective feed axes. In this research project, different control techniques to optimize the performance of SynRM need to be investigated and further developed. The basic for this is a sufficiently accurate motor model, which describes the current and rotor angle dependent motor characteristics. The necessary parameters shall be identified on a motor test bench via various load profiles. The main objective is the development of a system with high bandwidth and low torque ripple. To this purpose, non-linear controllers and Luenberger observer for the nested control loops will be investigated. An axis test bench with a real-time control system will be set up for validation purpose. This allows the developed methods to be tested and allows a comparative investigation of different motor types.