An Absolute Time-Grating Linear Displacement Sensor With a Multilayer Cascade Structure

This study presents a high-precision, long-range absolute time-grating linear displacement sensor based on a multilayer cascade structure. In the layer I structure, electric field coupling between the fixed and moving rulers generates an induction signal on the moving ruler. In the layer II structure, the transmitting stage receives this signal via internal wiring, and signal cascading is achieved through secondary coupling between the transmitting and receiving stages. The cascade structure makes full use of the available space above the fixed ruler, eliminating the need to expand the sensing areas of the fixed and moving rulers. This structure enhances signal strength through multilayer coupling and avoids the need for moving part leads. The sensor’s electrode array enables long-range measurements, with absolute positioning determined by a simple subtraction between two single-row incremental time-grating sensor signal phases, bypassing complex coding and decoding. Experimental analysis reveals traveling wave crosstalk, causing nonlinear measurement errors. Time-division multiplexing completely suppresses crosstalk and enhances measurement accuracy. After optimization, the sensor’s peak-to-peak measurement error is reduced by approximately three times, achieving an accuracy of $\pm 0.2~\mu $ m over a 400 mm range after compensation.