Disc Resonator Gyroscope(DRG)

Jared SatromChris Fruth

Goal of the Project

To conduct research and analysis of a novel MEMS gyroscope design1) 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 designs4) 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?