重复控制与积分正反馈组合的磁轴承低功耗控制

Low power control of magnetic bearing combined by repetitive control and positive integral feedback

本文提出一种重复控制与积分正反馈相结合的控制方法,以抑制磁轴承系统功耗。首先建立了磁轴承系统的数学模型,分析了由重力、转子不平衡和位移传感器噪声引起的电流噪声的频率特性,分析发现其可分为直流和多谐波两大类;其次推导了用于消除直流电流的控制器需满足的条件,在此基础上,设计了一种电流积分正反馈算法。通过调节转子的悬浮位置,利用混合磁轴承中永磁体产生的磁力抵消重力,抑制电流的直流分量,采用根轨迹方法确定保证闭环系统稳定的参数取值范围;然后提出一种嵌入式重复控制方法抑制转子不平衡和位移传感器引起的多谐波电流噪声,采用重构谱理论判定系统的稳定性。最后以磁悬浮控制力矩陀螺为测试平台,对所提出的控制算法进行仿真和实验研究。结果表明:采用该算法后,电流的直流分量基本被抑制,谐波分量的峰峰值减小了88.3%,功耗减小了7W,验证了该算法的有效性。

A control method combined by repetitive control and positive integral feedback was proposed to restrain system power consumption of magnetic bearing. Firstly, mathematical model of magnetic bearing system was established. Frequency characteristics of current noise caused by gravity, rotor imbalance and displacement sensor noise were analyzed, and found the current noise could be divided into two types of direct component and harmonic component. Controller conditions of eliminating di- rect current were deduced, a current positive integral feedback was designed. By adjusting suspension position of rotor, magnetic force produced by permanent magnet in hybrid magnetic bearing was used to offset gravity and suppress direct current component. A root locus method was employed to analyze the stability of the closed-loop system and to determine the parameters range. Then a plug-in repeti- tive control method was proposed to suppress multiple-harmonic current noise caused by rotor imbal- ance and displacement sensor. The absolute stability of the whole system was analyzed with the help of the regeneration spectrum. Finally, simulation and experimental research were implemented for proposed control algorithm taking magnetically suspended control moment gyro as test platform. Re- sults indicate that： after applying proposed algorithm, direct current component is suppressed basical- ly, peak-to-peak value of harmonic component is decreased by 88.3% and power consumption is de- creased by 7 W, which verifies effectiveness of the algorithm.