Disc Resonator Gyroscope (DRG) Jared Satrom Chris Fruth

Goal of the Project To conduct research and analysis of a novel MEMS gyroscope design 1) Understand the motivation for the new patent from Boeing and Honeywell and others; why higher performance? 2) Identify new features in the novel design(s) and how higher performances are achieved 3) Compare to existing gyroscope designs 4) Analyze Q (quality) factor improvements

Disc Resonating Gyro Basics

Disc Resonating Gyro Basics Gyroscope is driven to resonate in-plane Electrodes sense deflection in outer ring sockets Electrodes actuate in inner ring sockets Circuits process the signal and feedback into the system

Operation Principle of the DRG

Coriolis Effect Coriolis acceleration (a) occurs if a resonating disc is pterturbed Depends on velocities on the disc  higher frequencies allow Coriolis acceleration to dominate centrifugal acceleration Coriolis acceleration is what the electrodes sense through change in capacitance

How Does the DRG Work? DC Source creates an electrostatic force that moves the disc Proper control of these electrodes can put the system into resonance Similarly, the sensing electrodes use gap changes to gauge system changes

One Ring or Many? One major advantage of this system is its large area Compared to a single ring gyro, has much more control over actuation and sensing Single rings require flexible support beams as well

Why Cut the Circles? With full concentric circles, the structure tends to be rigid By using arcs instead, the structure becomes more flexible, allowing for better accuracy and performance

Ideal Gyro High-Q Large S/N ratio Low-cost Small (1 cm3) Reliable Requiring low power

Q-Factor Quality factor Q is the measure of energy dissipation

Issue: Energy Dissipation Mechanisms Thermoelasticity: Mechanical energy is exchanged for thermal energy that is diffused Scattering Loss: “Elastic wave” of resonation is scattered due to material defects Anchor Loss: Elastic waves travel down the support column of the disc and dissipate Fluid Damping: Less significant, only a problem for low frequency applications

Issue: Stiction and Electrode Damage

Benefits of this Design Has large sensing area compared to other gyros Easy to package Multiple sensing and driving electrodes can make it easier to operate and read

Fabrication

Fabrication

Advantages Over Other Designs MEMS gyroscopes desirable because they are lightweight and cheaper to produce Isolation from vehicle platform is desirable to limit transmission of external disturbances A design incorporating: high sensitivity (as in hemispherical resonators) simple/inexpensive thin planar Si microfabrication (as in a thin ring gyroscope)

Motivation for Higher Performance Scalability of previous gyroscope designs was poor: mechanical features were hard to perfect at smaller scales Sensor noise scales less than size Therefore, smaller yet more precise and accurate gyros are desired Adequate areas for driving and sensing while remaining compact

The Future of MEMS Gyros Smaller Cheaper Not limited to Silicon Ti  More durable Nano and Picosatellites Submarine & Aircraft satellite launches Image-stabilizing cellphones?

Questions?