A measurement system based on capacitance sensors for geometric errors of a miniaturized machine tool

Miniaturized machine tool (mMT) has been presented as a promising technique for machining miniature components due to its advantages such as miniaturized error sources, less heat dissipation and no limitation of the materials. To achieve submicron machining accuracy, geometric errors of a miniaturized machine tool should be accurately identified and compensated. In this paper, a novel multi-degree-of-freedom (DOF) measuring system is proposed for simultaneous measurement of two straightness, roll, yaw and pitch error motions along one moving axis of a miniaturized machining tool. The proposed system consists of five capacitance sensors and a sensing target. Readings of the sensors contain coupled information of all error motions. Based on homogeneous transformation matrix (HTM), the coupled relationships between the readings and error motions are obtained. An error estimation algorithm is developed for calculation of five geometric errors. Simulations are carried out to verify estimation accuracy and robustness of the algorithm