A High-Performance Tactical-Grade Monolithic Horizontal Dual-Axis MEMS Gyroscope With Off-Plane Coupling Suppression Silicon Gratings
Jian Cui, Qiancheng Zhao
Abstract
This articledemonstrates the developments toward a high-performance monolithic wheeled structure horizontal dual-axis [pitch ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X-</i> axis) and roll ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> -axis)] microelectromechanical system (MEMS) gyroscope based on off-plane coupling suppression silicon gratings. Gyroscopes have been fabricated with a silicon-on-glass fabrication process with vacuum sealed in metal packaging. The featured gyroscope operates in split mode with the bandwidths of two axes devices both of ∼70 Hz. By unitizing two individual active restraining control loops that adjust the quadrature amplitude via differentially biasing the silicon gratings in real time, the off-plane mechanical couplings of the two sense modes are significantly reduced by ∼95 and ∼30 times, which enables ∼25-fold and ∼56-fold improvements in the bias instability (BI) for a typical dual-axis device. Tactical-grade performances are achieved for both the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X-</i> axis and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y-</i> axis gyroscopes with angle random walk of 0.02 deg/√h and 0.045 deg/√h along with in-run BI of 0.26 deg/h and 0.65 deg/h, respectively, without any temperature compensation. The current preliminary results show great potential to achieve navigation grade precision by employing the mode-matching technique in the future. The use of silicon gratings for out-of-plane coupling reduction also provides an effective way to build a high-performance planar monolithic chip inertial measurement unit.