planar two-degree-of-freedom L-shaped capacitive displacement sensor based on time grating

Abstract Aiming to solve the problems of complex measuring systems, difficult synchronization, and complex decoupling algorithms when using two sets of high-precision one-dimensional sensing devices to measure two-dimensional displacement, A two-dimensional capacitive time grating displacement sensor is developed in this research. The sensor’s overall configuration comprises a fixed ruler and a moving ruler, both of which are installed in parallel and have a certain gap. Square excitation electrodes with dislocation coding in Y and X directions are arranged on the fixed ruler. The moving ruler is composed of three-square induction electrodes which are arranged in the form of a differential structure along Y or X direction. When the sensor works, four sinusoidal AC signals exhibiting a phase difference of π/2 are employed are successively applied to the adjacent four groups of excitation electrodes. Three traveling wave signals The induction electrodes yield displacement information for both the X and Y axes. The output signal can be decoupled at the same time by combining the decoupling formula. The displacement signal is converted into a square wave and the phase is compared with the reference signal, displacement in X and Y direction is finally obtained. Testing outcomes confirm that the peak-to-peak measurement error of the proposed sensor along the X and Y axes is 17.4μm and 18.2μm in the 300mm×300mm measurement range respectively, which provides a new technical way for plane two-dimensional displacement measurement with a large range and high precision.