Analytical Study and Thermal Compensation for Capacitive MEMS Accelerometer With Anti-Spring Structure

This paper presents the analytical modeling, calculation, experimental validation and feedback compensation of a capacitive MEMS accelerometer based on geometric antispring structure (GAS). According to the analytical thermal drift model, asymmetrical structure and the thermal variations in the operating environment result in accelerometer nonlinearity, temperature drift of scale factor (TDSF) and displacement bias (TDB), and were solved with a force-balanced capacitive readout, electronic active compensation and calibration system, respectively. The experimental characterization of the readout circuit indicates a high sensitivity, of 5.721 V/g, with a closed-loop nonlinearity of 30 ppm for ±1g operating range. The proposed analytical thermal drift model,confirmed by finite element analyses (COMSOL Multiphysics), predicts the thermal drifts of the bias and sensitivity. Without active compensation and calibration, the thermal drifts of the resonance frequency, bias and scale factor, for a temperature range from -10 °C to 90 °C, are measured to be, respectively, of 3361 ppm, 900 mg, and 2755 ppm; after the calibration and the active compensation feedback, these values are reduced to 121 ppm, 109 μg, 52.1 ppm, respectively. The Allan deviation was measured, in order to verify the effectiveness of the compensation methods, showing an initial uncompensated drift of 151μg in the temperature range from -10 °C to 90 °C, which is reduced to 41.7μg with DC-bias compensation. Therefore, the proposed force-balanced circuit, active compensation and calibration scheme, considerably reduces the temperature-induced drift of the capacitive MEMS accelerometer based on asymmetrical GAS.