Development of Self-Sensing Magnetic Bearings Using Variable-Switching-Frequency Amplifiers

本文研究了以可变开关频率放大器(滞环放大器)的开关信号作为反馈控制的磁悬浮轴承。该方法具有理论和实验两方面的特点。首先，根据电源类型和工作象限对滞环放大器进行分类。对每个放大器的动力学进行了解析研究。制作了每种类型的测试电路，实验证实了每种放大器的开关频率与悬浮体与电磁铁之间的间隙成正比，并证明了采用H桥驱动的磁滞放大器作为自传感磁悬浮轴承的功率放大器具有许多优点。它们是：(1)使用单极电源时，电流的上升和下降速度是相同的。(2)由于H桥交替地反转施加到线圈上的电压的极性，所以开关频率对电流指令对放大器的值不敏感。由于反馈的信号是以频率的形式给出的，因此控制系统的设计可以不同于传统的带有模拟式传感器的主动磁悬浮轴承。根据系统中的信号转换，将控制系统的结构分为：1)采用频率-电压转换器的控制系统(2)采用鉴相器的控制系统(3)采用逆变器的控制系统。阐明了每种控制系统的特点，并用这些控制系统实现了自感知悬浮。本文的研究结果为变频放大器自感知磁悬浮轴承的工业应用奠定了基础。计划开发一种利用自感知操作的小型磁悬浮轴承系统

This research investigated on seIf-sensing magnetic bearings using the switching signals of variable-switching-frequency amplifiers (hysteresis amplifiers) for feedback ccntroL The approach was both theoretical and experimental.First ; hysteresis amplifiers were classified based on the kind of power supply and the quadrants of operation. The dynamics of each amplifier was studied analytically. A test circuit of each type was manufacturect It was experimentally confirmed that the switching frequency of each amplifier was proportional to the gap between the suspended object and the electromagnet It was also shown that the hysteresis amplifier with an H-bridge drive had several advantages as power amplifiers for self-sensing magnetic bearings. They are(1) The speeds of increase and decrease of current are same although a unipoIar power supply is used.(2) The switching frequency in insensitive to the value of current command to the amplifier because the H-bridge reverses the polarity of the voltage applied to the coil alternatively.Second, the control system design of self-sensing magnetic bearings was discussed. Since the signal to be fed back in given in the form of frequency, the control system can be designed in different ways from those of conventional active magnetic bearings with analog type sensors. According to the signal conversions performed in the system, the configurations of control system are classified as1) Control system using frequency-to-voltage converters(2) Control system using phase detectors(3) Control system using countersThe characteristics of each control system were clarified Self-sensing suspension was achieved with these control systems.The results obtained by this research are fundamentaI and useful to promote industrial applications of the self-sensing magnetic bearings with variable- switching-frequency amplifiers. It is planed to develop a small-size magnetic bearing system by taking advantage of self-sensing operation