Origin and Compensation of Nonlinearity in Near-Navigation Grade Piezoresistive MEMS Gyroscope

The manuscript researches on nonlinearity sources in micro-electro-mechanical system (MEMS) yaw gyroscopes based on resistive sensing gauges with (250-nm)(2) cross section, coupled to a dedicated integrated circuit. Possible nonlinearity sources in the mechanical, electrical, and electronic domains are initially identified. A detailed investigation of all of them from a theoretical standpoint and/or from software simulations, indicates the Wheatstone half-bridge readout method and the electro-mechanical softening induced by the dc voltage applied at the quadrature electrodes as the predicted dominant sources. However, experimental measurements highlight how another source of linearity error appears for the proposed device, which is ascribed to the piezoresistive coefficient, with a negative-cubic (thus, sub-linear) trend. At the same time, the softening due to the dc voltage at quadrature compensation electrodes is expected to bring a positive-cubic (super-linear) effect. The dc voltage at the compensation electrodes is thus increased, according to the theoretical predictions. In the new situation, linearity errors are reduced by almost an order of magnitude down to 0.02% at the target full-scale range (FSR). The presence of nonlinearities of opposite sign, compensating one another after proper small voltage trimming, is unique to this piezoresistive sensing method.