力扰动对无传感器电磁轴承位移解调的影响

Influence from force perturbation to position demodulation in self-sensing active magnetic bearing

为了研究外力扰动对无传感器电磁轴承位移解调的影响机制,从电流型恒频开关功率放大器的调制原理出发,利用傅里叶级数、雅可比-安格尔恒等式、第一类贝塞尔函数等数学工具,在时域和频域内分析力扰动对电流纹波信号幅频特性的影响.理论分析表明,力扰动所引发的时变占空比会使电流纹波的开关频率处的谱线附近产生无数边频分量,各边频分量的幅值由第一类贝塞尔函数确定,边频分量间的频率间隔取决于占空比的变化频率.在电磁轴承系统平台进行相关实验,实验结果证明了理论分析的正确性.

A detailed analysis on the frequency characteristics of current ripple was proposed in both time domain and frequency domain in order to analyze the influence mechanism of force perturbation on position demodulation in self-sensing active magnetic bearings （AMBs） system. Fourier series, Jacobi-Anger identity, and the first kind of Bessel function were used based on the modulation principle of a current mode switching power amplifier with a fixed switching frequency. Theoretical analysis shows that the time-varying duty cycle introduced by the force perturbation causes innumerable side frequency around switching frequency of current ripple frequency spectrum. The amplitude of each side frequency is given by the first kind of Bessel function, and the frequency interval depends on the changing frequency of duty cycle. Experiments held on the AMBs platform verified the theoretical analysis.