Absolute Planar 2-D Time-Grating Displacement Sensor With Multifrequency Magnetic Field Time-Sharing Excitation

Aiming at the problems of cumulative error and the need to find zero when powering up the incremental planar 2-D time-grating displacement sensor, and the contradiction between increasing the sensor excitation signal frequency to obtain high signal-to-noise ratio and high resolution, an absolute planar 2-D time-grating displacement sensor structure based on multifrequency magnetic field time-sharing excitation is designed. First, an absolute planar 2-D time-grating measurement model with the prime structure of the opposite poles is established, and a new 2-D absolute position solution based on the lookup table method is proposed. The feasibility of this solution is verified by electromagnetic field simulation, and the optimal mounting gap of the sensor is determined to be 0.8 mm and established; a new 2-D absolute position solution based on table lookup is proposed, the feasibility of this solution is verified by electromagnetic field simulation, and the optimal mounting gap of the sensor is determined to be 0.8 mm. Based on the lookup table, a method is proposed, the feasibility of this solution is verified by electromagnetic field simulation, and the optimal mounting gap of the sensor is determined to be 0.8 mm. The new decoupling method of heterodyne down frequency can obtain a purer traveling wave signal, improve the signal-to-noise ratio of the sensor, and ensure a high resolution, with the resolution in the x- and y-directions of 0.07 and $0.28~\mu $ m, respectively. Finally, a prototype of the sensor is fabricated and a 2-D precision experimental platform is built for the performance test. The experimental results show that compared with the original direct decoupling method, the x- and y-direction accuracies of the new method of decoupling by heterodyne down frequency have been improved by 27.5% and 20.5% within 8 mm of the pitch, and the original measurement errors of the sensors in the x- and y-directions in the effective measurement range of 147 $\times $ 147 mm are ±16.1 and $\pm 17.2~\mu $ m, respectively.