A high-Q birdbath resonator gyroscope (BRG)

Abstract

We report a three-dimensional (3-D) micro-scale shell gyroscope made of fused silica (FS), called the birdbath resonator gyroscope (BRG). The BRG operates at 10.45 kHz, far above most environmental noise frequencies, and offers high mechanical quality factor (Q n=2 = 249k) and low stiffness and damping anisotropy (Δf n=2 = 14 Hz, Δ1/τ n=2 = 4.1 mHz). The birdbath (BB) resonator can be fabricated with good structural symmetry because its anchor is self-aligned to the rest of the structure. The BB resonator also has large frequency separation between the n=2 wineglass modes and the closest parasitic mode (|f parasitic -f n=2 |/f n=2 = 0.3), which makes the gyro less sensitive to vibration. The BRG is fabricated using a 3-D µ-blow-torching process and assembly on an electrode substrate made with the SiliconOn-Glass (SOG) process. The BRG is operated in the force-rebalance mode at <1 mTorr vacuum and room temperature, and has a scale factor of 27.9 mV/(deg/sec), a full-scale range >400 deg/sec, an angle random walk (ARW) of 0.106 deg/√hr and a bias stability of 1 deg/hr.

High resolution micro ultrasonic machining (HR-&#x03BC;USM) for post-fabrication trimming of fused silica 3-D microstructures

“…This work used bird-bath (BB) shells (Fig. 6), which are being investigated for use in rate integrating gyroscopes [9]. These structures have a diameter of 5 mm, and a height of 1.55 mm, whereas the average thickness of the shell is only 70 µm.…”

“…These structures have a diameter of 5 mm, and a height of 1.55 mm, whereas the average thickness of the shell is only 70 µm. The trimming of these shells is needed for refining structural [9].…”

Demonstration of 1 Million <inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula>-Factor on Microglassblown Wineglass Resonators With Out-of-Plane Electrostatic Transduction

“…Q-factors up to 24k [4] were measured on poly-diamond wineglass shells deposited in pre-etched cavities and up to 20k were measured on sputtered Ultra Low Expansion (ULE) glass shells deposited on precision ball lenses [5]. Q-factors as high as 7.8k was demonstrated on blow-molded bulk metallic glass shells [6] and 1 million on fused silica shells [7].…”

Out-of-plane electrode architecture for fused silica micro-glassblown 3-D wineglass resonators

“…There is an interest in 3-D MEMS wineglass resonator architectures for use in next-generation inertial sensing applications due to potential advantages in symmetry, minimization of energy losses, immunity to external vibrations and die stresses [1]- [5].…”

“…Q-factors up to 24k [2] were measured on poly-diamond wineglass shells deposited in pre-etched cavities and up to 20k were measured on sputtered ultra low expansion (ULE) glass shells deposited on precision ball lenses [3]. Q-factors as high as 7.8k was demonstrated on blow-molded bulk metallic glass shells [4] and 1 million on fused silica shells [5].…”