Transcript MEMS Gyro - Northwestern University

Disc Resonator Gyroscope
(DRG)
Jared Satrom
Chris Fruth
Goal of the Project
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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
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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
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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?
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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?
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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
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High-Q
Large S/N ratio
Low-cost
Small (1 cm3)
Reliable
Requiring low power
Q-Factor
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Quality factor Q is the measure of energy
dissipation
Issue: Energy Dissipation Mechanisms
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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
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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
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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:
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high sensitivity (as in hemispherical resonators)
simple/inexpensive thin planar Si microfabrication
(as in a thin ring gyroscope)
Motivation for Higher Performance
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Scalability of previous gyroscope designs
was poor:
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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
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Adequate areas for driving and sensing while
remaining compact
The Future of MEMS Gyros
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Smaller
Cheaper
Not limited to Silicon
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Nano and Picosatellites
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Ti  More durable
Submarine & Aircraft
satellite launches
Image-stabilizing
cellphones?
Questions?