Hourglass-beam Nanogram-proof-mass Array: Toward a High Dynamic Range Accelerometer

This paper reports on the development of a monolithic capacitive accelerometer array system with a designed full-scale range of $\pmb{\pm 50\mathrm{KG}}$, measured velocity random walk (VRW) of $\pmb {14} \mu \mathrm{G}\cdot\surd{}\mathrm{h}$ and measured bias stability of 14 mG, corresponding to an effective dynamic range of 131 dB. An hourglass-beam flexure is devised to evenly distribute the distortion strain energy over the length of the flexure upon acceleration. Given the maximum targeted input acceleration and constrained by fabrication critical dimensions, the hourglass spring beam design is optimized to achieve the highest transducer sensitivity and thus maximizing the transducer dynamic range. A MEMS-array compensation technique is proposed to null the charge imbalance from transducer offset. Independent modulation voltage control on a 2-cell array and 182-cell array in parallel connection enable fine-grain offset compensation and coarse-grain offset compensation, respectively.