基于频分复用的多路微电容检测技术

Frequency Multiplexing-Based Multi-Axis Capacitive Position Detection for an Electrostatically Levitated Micromotor

为使静电悬浮微电机的环形转子稳定悬浮在定子电极腔体的几何中心,需要采用差动电容式传感器检测转子沿五个自由度的运动,然后通过静电悬浮控制系统实现有源静电支承。根据频分复用原理,设计了一套可检测悬浮式转子五个自由度运动的微电容检测电路。采用多路高频正弦信号作为载波加载至与各自由度对应的控制/检测电极上,通过公共电极输出反映转子沿各自由度位移变化的调幅信号,然后经过交流放大、相敏解调、低通滤波后得到各自由度位移检测信号。文中介绍了微电容检测电路的组成及原理,分析了电路特性,给出了x轴检测电路的测试结果。实验表明,检测电路的灵敏度为23.3 V/pF,通频带为10.58 kHz,零位稳定性优于0.1 mV。

To maintain the ring-shaped microrotor electrostatically suspended in the geometric center of the cavity shaped by the stator electrodes, a set of differential capacitance-based position sensors is used to sense the rotor’s motion in five degrees of freedom （DOFs） and utilized to realize active electrostatic suspension. Based on frequency multiplexing method, a set of micro-capacitance detecting circuits is presented with an aim to sense the motion of the motor in five DOFs. By applying high-frequency sinusoidal carrier to associated control/sensing electrodes, an amplitude-modulated signal which indicates the rotor’s position in each DOF is formed from the common electrodes. The amplitude-modulated signals are then amplified, demodulated and low-pass filtered sequentially in order to obtain a readout voltage of the rotor position. The paper describes the operating principle, the design and the performance evaluation in both simulation and experiment. The experimental results show that the sensitivity is 23.3V/pF, the bandwidth is 10.58kHz and the zero stability is less than 0.1mV.