电容法微力测量中轴偏对电容梯度的影响

Effect of electrode offset on capacitance gradient in micro force measurement based on capacitive sensor

电容法微小力值测量中电容传感器会存在轴偏现象,影响测量精度。基于理论模型,分析计算了电容传感器在轴偏情况下的电容梯度。设计了合理的测量方案,通过高精度图像传感器及机器视觉算法,实现了轴偏及电容梯度测量,对轴偏与电容梯度之间理论数值关系进行了实验验证。实验证明了理论推导的正确性及测量方案的可性行,为后续的微力精密测量提供了误差补偿依据。在当前的电容传感器条件下,轴偏不大于50μm时,可满足误差1%以内的系统整体测量目标。

In the measurement of micro force with capacitive sensor, the accuracy may be affected by the offset of electrodes. Based on the theoretical model, the capacitance gradient of the cylindrical capacitive sensor with offset was analyzed and calculated. A reasonable method to measure the electrode offset and capacitance gradient with high-precision image sensors and machine vision algorithm was proposed. Furthermore, some experiments were done to verify the relationship between electrodes offset and capacitance gradient. The result proves the correctness of theoretical derivation and the feasibility of measuring programs, and also offers a basis for the error compensation of subsequent measurement. With current capacitive sensor, tolerance of 1% can be satisfied when the offset is no more than 50 μm.