Theoretical analysis and design improvement of nonlinearity in capacitive accelerometers

This paper systematically conducts theoretical analysis, structural improvement design, finite element simulation verification, and mathematical compensation model research focusing on the nonlinear characteristics of capacitive comb-drive accelerometers. First, the structural design and fabrication process of the accelerometer are presented. Then, the generation mechanism of nonlinear errors is theoretically analyzed from three dimensions: structural design, fabrication error, and testing. Research results show that: the mass bias displacement, unilateral deformation of the substrate, and installation errors significantly increase the sensitivity asymmetry of the accelerometer, further leading to the deterioration of nonlinearity. This paper proposes a single-anchor layout design with parallel arrangement in the sensing direction. Finite element simulation confirms that the nonlinearity of the improved accelerometer caused by mass bias displacement is reduced by 96.36 %; under the same substrate bending amount, the nonlinearity of the improved accelerometer is reduced by 34.72 %. To address the installation error issue, a corresponding mathematical compensation model is constructed. Within the operating range of comb finger gap variation of ±7 %, the nonlinearity of the compensated open-loop accelerometer is reduced by 67.11 %, which can be stably controlled below 900 ppm.