Initial Demonstration of a Closed-Loop Two-Axis MEMS Accelerometer with Quasi-Zero Effective Stiffness

This study proposes a stiffness-tunable 2-axis MEMS accelerometer. By tuning the effective stiffness of both axes to nearly zero with double-sided parallel plate (DSPP) capacitors, the 1/f noise in displacement detection can be significantly reduced. By employing force rebalance control to maintain the proof mass at a fixed position, this accelerometer effectively mitigates cross-axis errors arising from the nonorthogonality of the elastic axis and crosstalk of displacement detection signals between orthogonal axes. A motion decoupling structure is designed to isolate crossing-axis components of the feedback force, thus further suppressing cross-axis errors. Experimental results indicate Allan variances bias instability for the x and y axes as 13.9μg and 13.8μg, respectively, with a cross-axis sensitivity amounting to only 0.28%.