Design and characterisation of closed-loop nested biaxial MEMS accelerometers

Abstract This paper investigates a nested biaxial MEMS (Micro-Electro-Mechanical Systems) accelerometer with low coupling error, derives the kinetic model equations of the accelerometer, and performs finite element simulations of the operating modes and mechanical coupling of the structure. The biaxial accelerometer adopts an inner and outer nested structure with non-rigid links, aiming to reduce the cross-coupling between orthogonal sensitive axes. Closed-loop control is used to further improve the stability of the device and reduce the coupling coefficient. The coupling coefficients of the accelerometer were derived by capacitance analysis. A process based on silicon on glass (SOG) was designed, which is a mature technology with low cost, good processing consistency, high yield and good compatibility with capacitive structures. The preparation and testing of the structure was finally completed. The test proves that the accelerometer works in closed-loop with low cross-coupling, and the inter-axis cross-coupling coefficients are less than 0.01% and 0.012%, respectively. The accelerometer outputs a noise density of 52.69 ug/√Hz with a zero-bias stability of 38.46 ug in the X -axis and 82.99 ug/√Hz with a zero-bias stability of 55.61 ug in the Y -axis. The output sensitivities of the two axes reach 71.49 mV g −1 and 55.4 mV g −1 , respectively, in the ± 1 g flip-flop experiment.