Investigation of the Magnetic Flux Bypass Compensation Method for Distance and Angle Measuring Systems

现代电驱动、磁轴承和无轴承电机需要一个或多个测量系统来确定距离和旋转角度。为此，越来越多地使用无传感器系统，与有传感器的系统相比，无传感器系统通常更简单、更坚固、更紧凑、更具成本效益并且对外部影响不太敏感。然而，先前的无传感器方法存在两个主要问题。首先，信噪比低，限制了测量精度或系统的动态特性。第二，系统对磁饱和敏感。饱和度不仅影响测量信号，而且影响测量灵敏度。即使在相对较低的平均通量密度下，这也可以变为零。在这种情况下，实际测量变量和测量值之间的关系不再是双射的，因此，为这种无传感器系统的构建和后续评估开发了一种新的方法。与先前的方法一样，不再需要对电流信号进行微分，而是已经通过感应定律进行了微分。这消除了对复杂的高带宽电流测量的需要，并大大提高了信噪比。此外，饱和效应通过磁通旁路来补偿。一方面，这允许实现测量信号对饱和度的低得多的依赖性。另一方面，与先前的方法相比，测量灵敏度仅在显著更高的通量密度下消失。由于不需要单独的载波电压、低通滤波器或解调器，系统的带宽非常高。对于使用流量旁路法的测量系统的装配和电子评估，仅需要电机工程中的标准部件。在拟建项目范围内，应研究流量旁路法的准确度、信噪比和最大允许饱和度的技术物理限值。进一步的研究课题是磁通旁路的材料和几何形状的影响，以及它们的合适尺寸和对外部影响的敏感性。使用一个实验装置的无传感器磁通旁路测量系统的旋转角度和距离的测量结果进行了验证。

Modern electric drives, magnetic bearings and bearingless motors require one or more measuring systems for the determination of distances and rotation angles. For this purpose, sensorless systems are increasingly being used, which are usually simpler, more robust, more compact, more cost-effective and less sensitive to external influences than systems with sensors. However, there are two main problems with previous sensorless methods. First, the signal-to-noise ratio is low and limits the measurement accuracy or the dynamics of the system. Second, the system is sensitive to magnetic saturation. The degree of saturation influences not only the measurement signal, but also the measurement sensitivity. Even at relatively low mean flux densities this can become zero. In this case, the relationship between the actual measured variable and the measured value is no longer bijective.Therefore, a new method was developed for the construction and subsequent evaluation of such a sensorless system. A differentiation of the current signal, as with previous methods, is no longer necessary, but already takes place via the induction law. This eliminates the need for complex high bandwidth measurement of the current and considerably increases the signal-to-noise ratio. In addition, the saturation effect is compensated by means of a flux bypass. On the one hand, this allows a much lower dependence of the measurement signal on the degree of saturation to be achieved. On the other hand, the measurement sensitivity only disappears at significantly higher flux densities compared to previous methods. Since no separate carrier voltage, low-pass filters or demodulators are required, the bandwidth of the system is extremely high. For the assembly and electronic evaluation of a measuring system using the flow-bypass method, only components that are standard in electrical machine engineering are required.Within the scope of the proposed project, the flux bypass method is to be investigated with regard to the technical-physical limits for the accuracy, the signal-to-noise ratio and the maximum permissible degree of saturation. Further subjects of investigation are the influence of the material and the geometry of the flux bypass and their suitable dimensioning as well as the sensitivity to external influences. The results are verified using an experimental set-up of a sensorless flux bypass measurement system for the measurement of both rotation angles and distances.