High-Q Fused Silica Micro-Shell Resonators for Navigation-Grade MEMS Gyroscopes

Abstract:

Many technologies rely on GPS for navigation, but reliable satellite signals are not always available. "Dead reckoning" navigation of airplanes and deep space satellites using inertial sensors has been demonstrated with macro-scale gyroscopes, but they are too large, expensive, and power-hungry for most applications. Shrinking their size and cost will have widespread benefits for a range of defense and consumer applications, including munitions, autonomous vehicles, drones, and virtual reality; however, mechanical and electronic noise in existing MEMS gyroscopes tend to cause unacceptable drift.

To quiet the noise, a fused silica resonator for a high-performance MEMS gyroscope has been developed. This hemitoroidal micro-shell, known as the birdbath resonator, is formed with blowtorch reflow molding in only ten seconds. Its vibratory decay time constants in the hundreds of seconds and quality factors in the millions are the best in its class, helping to reduce angle random walk and bias instability, two critical parameters that MEMS gyroscopes struggle with. This defense details the journey of identifying and mitigating the dominant energy loss mechanisms that led to this unprecedented performance, bringing compact and affordable dead reckoning closer to reality.