【作者】 唐明；

【导师】 祝长生；

【作者基本信息】 浙江大学 ， 电机与电器， 2013， 博士

【摘要】 自传感主动电磁轴承系统具有硬件精简、成本低廉、设计简便、执行器和传感器为同一部件等等一系列独特的性能优势,因而成为近年来电磁轴承领域最具革新意义的热门课题之一本文在采用恒频电流型PWM开关功率放大器的主动电磁轴承系统平台中,研究了基于PWM信号的电磁轴承自传感技术。从理论分析、仿真研究、实验验证三个方面全方位地对PWM信号这一高频源在自传感技术中的应用进行了深入而细致的研究。在基础理论和关键技术方面获取了一些自主创新的研究成果：1.建立了主动电磁轴承系统的电感模型,在忽略磁场饱和、漏磁、磁滞、涡流等非线性因素的条件下,推导出了电磁线圈等效电感和气隙长度的函数关系式,证明气隙长度可以由电磁线圈等效电感的变化来进行估计,该结论是电磁轴承系统实现自传感运行的重要理论基础。2.研究了恒频电流型PWM开关功率放大器的拓扑结构与工作原理,使用傅里叶级数的方法对电磁线圈两端的电压信号、电磁线圈中的电流信号进行了谐波分析,推导出了电流高频纹波幅值关于气隙长度和PWM信号占空比的函数关系式。3.使用雅可比-安格尔恒等式、第一类贝塞尔函数等数学工具研究了力扰动对电流高频纹波信号的频谱特性影响,理论分析和实验结果表明力扰动通过控制器的反馈作用,使得功率放大器在跟踪动态给定电流信号时产生了时变的占空比。时变的占空比不仅影响着电流纹波高频分量的幅值,而且使其频谱不再单一。电流纹波在开关频率处的谱线周围会出现无数的等间隔边频分量,这些边频分量的频率间隔与电流参考信号的频率相等。各阶边频分量的幅值由第一类贝塞尔函数的值确定。4.考虑到电流高频纹波的特殊频谱特性,在帕塞瓦尔定理的基础上详细探讨了解调器中带通滤波器的通带增益、通带带宽等参数对解调器性能的影响,并给出了各参数的选择范围。在此基础上,基于UAF42芯片设计了一款改进型解调器,并通过仿真和实验验证了该解调器的性能。5.提出一种采用占空比补偿的电磁轴承自传感技术,通过对DSP28335芯片资源的充分利用,将自传感技术的硬件复杂度降低了一半。将占空比补偿策略所估计得到的转子位移作为反馈信号,成功地实现了四自由度径向电磁轴承系统在0-3000rpm内稳定的自传感运行。6.提出一种采用非线性参数估计法的电磁轴承自传感技术,通过嵌入一个与实际系(?)参数相等的电磁轴承等效模型和简单PI控制器,实现了对转子位移的闭环估计。仿真结果表明,相比其他开环位移估计策略该方法能够有效的提高位移提取的精度和带宽。将非(?)性参数估计法估计得到的转子位移作为反馈信号,能够实现四自由度径向电磁轴承系统(?)0-3000rpm内稳定的自传感运行,且性能明显优于占空比补偿法。更多还原

【Abstract】 Self-sensing active magnetic bearing has a series of unique performance advantages including:integrated hardware, low cost, simple designed, actuator acts as sensor and etc, so it is the most innovative field in the scope of magnetic bearing.This dissertation intended to research the self-sensing technology based on the PWM signal on the active magnetic bearing platform which employs fixed frequency current mode power amplifier. The self-sensing technology employing PWM signal as high frequency injection had been thorough and detailed studied with respect to theoretical analysis, simulated research and experimental verifications. Some independent-innovative achievements on the basic theory and key technology are obtained:1. The inductor model of the active magnetic bearing was created, and then, the functional relationship between coil equivalent inductance and air gap was obtained under the assumptions that magnetic saturation, flux leakage, hysteresis and eddy current are all ignored. The air gap can be estimated by the variation of the coil inductance, and this conclusion is an important foundation for the self-sensing active magnetic bearing.2. Topology and operation principle of the fixed frequency current mode power amplifier were studied. Harmonic analysis on coil voltage and current was carried out using Fourier series. The functional relationship between current ripple amplitude, air gap and PWM duty cycle was obtained.3. Jacobi-Angle identity, the first kind of Bessel function and other mathematical tools were employed to research the influence on the frequency characteristic of current ripple from the force disturbance. Theoretical analysis and experimental results showed that time-varying duty cycle is generated when power amplifier tracks the command signal which caused by force feed through. The amplitude of the current ripple and its frequency component are both influenced by the time-varying duty cycle. Infinite side frequency spectrum with the same interval appears around the spectrum component at switching frequency, and the frequency interval equals to the frequency of current reference signal. The amplitude of each side frequency component is given by the first kind of Bessel function.4. Considering of the special frequency spectrum characteristics of the current ripple, the effect of pass band gain and pass band width, the main parameters of the band pass filter in the demodulator, on the demodulator’s performance was discussed in detail based on the Parseval theorem. The proper range of each parameter was given. An improved demodulator was designed using UAF42, simulation and experiment result verified its performance.5. A self-sensing strategy on magnetic bearing by duty cycle compensation was proposed. The hardware complexity was reduced to half by utilizing the on-chip resource of DSP28335. The position estimation from the duty cycle compensation strategy was used as feedback signal, and the four degree of freedom radial active magnetic bearing was steadily suspended within0-3000rpm.6. A self-sensing strategy on magnetic bearing using nonlinear parameter estimation was proposed. The closed-loop estimation of the rotor position was achieved by employing a simple PI controller and a magnetic bearing model which has the same parameters to the real one. Simulation results proved that, comparing to other open loop position estimation strategy, this method can greatly improve the accuracy and bandwidth of the estimator. The position estimation from the nonlinear estimator was used as feedback signal, and the four degree of freedom radial active magnetic bearing system achieved satisfactory performance within0-3000rpm, which obviously superior to that of duty cycle compensation strategy.更多还原