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MEMS GyroscopeAaron Burg
Azeem Meruani
Michael WickmannRobert Sandheinrich
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Gyroscopes
Intro to Gyroscopes
Draper Tuning fork Gyroscope
Piezoelectric GyroscopeAbsolute Angle Measurement using aGyroscope
Optical Gyroscope and limitationsApplications
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Intro to Gyroscopes
Traditional Gyroscopes
Working Principle
Transition to MEMSTypes of Gyroscopes
Piezoelectric
Vibratory Ring Laser
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Laser Ring Gyroscopes
Two signals sent around ring
Different path lengths create abeat frequency.
Aarea of ring
Pperimeter of ring
p
A
4
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Dead Band
Dead Band -No changein beat frequency forsmall rotation rates
Due to frequency lock-in
r- backscatteringamplitude
A
crL
2
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Scaling Difficulties
Derived Equation for Laser Gyroscope
Beat Freq = (M) Angular Velocity - 1/M
Dead Band = 1/M^2
M = Scaling Factor
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Scaling Difficulties
M = 10-4
-Dead Band = 108 timesbigger
-Time varying term larger
-Slope of response lower
Change Bandwidth
To lower Dead Band, wavelengthcould be decreased.
Lower slope DecreasedSensitivity
A
crL
2
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Draper Tuning Fork Gyro
The rotation of tinescauses the CoriolisForce
Forces detectedthrough eitherelectrostatic,electromagnetic orpiezoelectric.
Displacements aremeasured in theComb drive
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Advancements
Improvement of drift
Improvement ofresolution
0
0.2
0.4
0.6
0.8
1
1.2
drift '93 drift '98
Deg
/hr
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Resolution '93 Resolution ' 94 Resolution '97
Deg
/hr
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Performance Advantages
No change in performance due totemperature
Lower voltage noise
Stronger signal to noise ratio
Better communication with external devices
Higher sensitivity
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Piezoelectric Gyroscopes
Basic Principles
Piezoelectric plate withvibrating thickness
Coriolis effect causesa voltage form thematerial
Very simple design
and geometry
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Piezoelectric Gyroscope
Advantages
Lower input voltage than vibrating mass
Measures rotation in two directions with asingle device
Adjusting orientation electronically is possible
Disadvantages
Less sensitive
Output is large when = 0
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Absolute Angle Measurement
Bias errors cause a drift while integrating
Angle is measured with respect to thecasing
The mass is rotated with an initial
When the gyroscopes rotates the masscontinues to rotate in the same direction
Angular rate is measured by adding adriving frequency d
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Design consideration
Damping needs to becompensated
Irregularities in
manufacturingAngular ratemeasurement
For angular rate measurement
Compensation force
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APPLICATIONS
Anti-Lock Brakes
Military Munitions
Inertial Measurement UnitGait-Phase Detection Sensor Embeddedin a Shoe Insole
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Anti-Lock Brakes
Use of Draper Tuning Fork Gyroscope
Yaw Rate Sensor for skid control
Tested under rigorous temperature conditions
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Inertial Measurement Unit
Honeywell acquiredDrapers Tuning Forktechnologies
Replaced Ring LaserGyro in originaldesign
Developed a low-cost,
micro-device capableof accuratelymeasuring rates anddisplacements
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Munitions Controls
Draper Laboratories workingwith Office of Naval Researchto develop countermeasure-proof munitions
Tuning Fork Gyroscope usedfor positioning and rates ofdisplacement
Gyro allows for inertialmovement, bypassingcountermeasures
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Gait-Phase Detection sensorEmbedded in a Shoe Insole
Measures the angular velocity of the foot
Used to activate a functional electrical stimulatorattached to the foot.
Over 96% accuracy
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Conclusion