Disc Resonator Gyroscope (DRG)

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Disc Resonator Gyroscope(DRG)

• Jared Satrom
• Chris Fruth

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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

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Disc Resonating Gyro Basics
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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

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Operation Principle of the DRG
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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

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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

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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

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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

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Ideal Gyro

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

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Q-Factor

• Quality factor Q is the measure of energy
  dissipation

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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

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Issue Stiction and Electrode Damage
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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

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Fabrication
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Fabrication
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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)

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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

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The Future of MEMS Gyros

• Smaller
• Cheaper
• Not limited to Silicon
• Ti ? More durable
• Nano and Picosatellites
• Submarine Aircraft satellite launches
• Image-stabilizing cellphones?

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Questions?