Investigation of synchronous reluctance motors for feed drives in machine tools

目前，机床行业中使用最广泛的进给驱动和辅助驱动的电机类型是高性能的永磁同步电机。然而，这种主要由关键稀土元素组成的永磁体的生产非常昂贵，而且不符合生态环境。由于原材料价格的波动和全球在价格和质量方面的竞争，对具有成本效益和生态可持续的机床部件解决方案的需求正在增加。永磁同步电机的一个可能的替代方案是所谓的同步磁阻电机(SynRM)，由于它没有永磁体，在过去的几年里变得越来越有吸引力。通过优化转子的几何结构，以前已知的缺点，如扭矩波动和噪声已经显著减少。市场上的商用SynRM显示出低于2%的扭矩波动。由于其坚固的结构和即使在部分负载下的高能效，同步电机现在被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是否以及在多大程度上可以用作机床中进给轴和辅助轴的驱动电机。其中，目的是研究控制算法改善转矩脉动的潜力，并比较分析不同电机类型的机床轴的动态行为。与永磁同步电机类似，同步电机的速度可以很容易地通过逆变器进行控制。对进给传动轴的初步仿真研究表明，同步电机可以应用于高性价比的进给轴。在这个研究项目中，需要研究和进一步发展不同的控制技术来优化同步电机的性能。实现这一点的基础是一个足够精确的电机模型，它描述了电流和转子角度相关的电机特性。应在电机试验台上通过各种负载曲线确定必要的参数。主要目标是开发一种具有高带宽和低转矩脉动的系统。为此，将研究嵌套控制回路的非线性控制器和Luenberger观测器。为了验证，将建立一个带有实时控制系统的轴系试验台。这允许对开发的方法进行测试，并允许对不同电机类型进行比较研究。

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.