Self-Sensing Magnetic Bearings: Development of Virtual Probes

本研究的目的是通过使用测量放大器电压和电流实现虚拟位置探头，开发和演示一种商业上可行的主动磁轴承自传感技术。将采取两种可能的办法。第一种方法将放大器、磁致动器和转子轴颈组成的系统视为由转子位置参数化的线性对象：参数观测器利用开关放大器提供的持续激励来确定该参数（转子位置）。第二种方法利用全转子与作动器的线性周期模型，并为该系统构造状态观测器。基于这两种方法的虚拟探头（观察者）将以硬连线电子形式实现，或者理想情况下，作为数字现场可编程门阵列。在任何一种情况下，所得到的估计（虚拟探头）硬件的性能将使用现有的磁轴承支持的转子进行检查，并与传统的涡流型比邻器进行比较。本研究的主要好处是降低了主动磁轴承硬件的复杂性。通过从轴承暴露的恶劣环境中去除组件，可以大大提高这些设备的成本和可靠性。这极大地增强了磁轴承在许多重要技术中的应用，从用于分布式发电的微型燃气轮机到用于治疗充血性心力衰竭和其他类似心脏疾病的植入式人工心脏。硬件的复杂性和可靠性是磁性轴承在这些和许多其他应用中大规模商业使用的主要障碍：自传感是减少这些问题的关键一步。这项研究的一个诱人的长期利益和中心目标是开发真正的“现成的”磁轴承，它可以像传统的流体膜或滚动元件轴承一样销售。通过消除位置传感器，在接近一个关键的“被动”属性，确保轴承将稳定地支持任何稳定的转子显著障碍被移除。这意味着主动磁轴承可以在不针对每个特定应用进行定制的情况下销售，避免了非常昂贵的工程工作，并刺激了规模经济，这对于释放主动磁轴承技术的新兴商业潜力至关重要。

The objective of this research is to develop and demonstrate a commercially viable technique for self-sensing in active magnetic bearings by realizing a virtual position probe using measured amplifier voltage and current. Two potential approaches will be pursued. The first treats the system comprised of amplifier, magnetic actuator, and rotor journal as a linear plant parameterized by rotor position: a parameter observer takes advantage of persistency of excitation provided by switching amplifiers to determine this parameter (rotor position). The second approach exploits a linear periodic model of the full rotor in combination with the actuator and constructs a state observer for this system. Virtual probes (observers) based on both approaches will be implemented either in hardwired electronic form or, ideally, as a digital field programmable gate array. In either case, the performance of the resulting estimation (virtual probe) hardware will be examined using an existing magnetic bearing supported rotor and compared to conventional eddy current type proximitors.The principal benefit of this research is to reduce the complexity of hardware in active magnetic bearings. By removing components from the harsh environment to which the bearings are exposed, the cost and reliability of these devices can be improved substantially. This greatly enhances the application of magnetic bearings to a number of important technologies ranging from micro gas turbines for distributed electric power generation to implantable artificial hearts for treatment of congestive heart failure and other similar cardiac ailments. Hardware complexity and reliability is a major obstacle to large-scale commercial use of magnetic bearings in these and many other applications: self-sensing is a pivotal step in reducing these problems. A tantalizing long term benefit and central goal of continuation of this research is development of truly "off-the-shelf" magnetic bearings which can be marketed in the same manner as conventional fluid film or rolling element bearings. By eliminating the position sensor, a significant hurdle is removed in approaching a critical "passivity" property which ensures that the bearing will stably support any stable rotor. This would mean that active magnetic bearings could be sold without tailoring them to each specific application, avoiding very costly engineering effort and stimulating the economies of scale critical to unlocking the nascent commercial potential of active magnetic bearing technology.