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Gyroscope
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MEMS GyroscopeAaron BurgAzeem MeruaniMichael WickmannRobert Sandheinrich
GyroscopesIntro to GyroscopesDraper Tuning fork GyroscopePiezoelectric GyroscopeAbsolute Angle Measurement using a GyroscopeOptical Gyroscope and limitationsApplications
Intro to GyroscopesTraditional GyroscopesWorking PrincipleTransition to MEMSTypes of GyroscopesPiezoelectricVibratoryRing Laser
Laser Ring GyroscopesTwo signals sent around ringDifferent path lengths create a beat frequency.
A area of ringP perimeter of ring
Dead BandDead Band -No change in beat frequency for small rotation ratesDue to frequency lock-in
r- backscattering amplitude
Scaling DifficultiesDerived Equation for Laser Gyroscope
Beat Freq = (M) Angular Velocity - 1/M Dead Band = 1/M^2
M = Scaling Factor
Scaling DifficultiesM = 10-4 -Dead Band = 108 times bigger-Time varying term larger-Slope of response lower
Change Bandwidth
To lower Dead Band, wavelength could be decreased.Lower slope Decreased Sensitivity
Draper Tuning Fork GyroThe rotation of tines causes the Coriolis ForceForces detected through either electrostatic, electromagnetic or piezoelectric.Displacements are measured in the Comb drive
AdvancementsImprovement of driftImprovement of resolution
Chart3
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0.1
Deg / hr
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driftResolution
drift '9314000Resoultion
drift '980.1100
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Deg / hr
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4000
1000
100
Deg / hr
Sheet1
driftResolution
drift '9314000Resolution '93
drift '980.11000Resolution ' 94
100Resolution '97
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Deg / hr
Sheet2
Deg / hr
Sheet3
Performance AdvantagesNo change in performance due to temperature Lower voltage noise Stronger signal to noise ratioBetter communication with external devicesHigher sensitivity
Piezoelectric GyroscopesBasic PrinciplesPiezoelectric plate with vibrating thicknessCoriolis effect causes a voltage form the materialVery simple design and geometry
Piezoelectric GyroscopeAdvantagesLower input voltage than vibrating massMeasures rotation in two directions with a single deviceAdjusting orientation electronically is possibleDisadvantagesLess sensitiveOutput is large when = 0
Absolute Angle MeasurementBias errors cause a drift while integratingAngle is measured with respect to the casingThe mass is rotated with an initial When the gyroscopes rotates the mass continues to rotate in the same directionAngular rate is measured by adding a driving frequency d
Design considerationDamping needs to be compensated Irregularities in manufacturingAngular rate measurement
For angular rate measurementCompensation force
APPLICATIONSAnti-Lock BrakesMilitary MunitionsInertial Measurement UnitGait-Phase Detection Sensor Embedded in a Shoe Insole
Anti-Lock BrakesUse of Draper Tuning Fork GyroscopeYaw Rate Sensor for skid controlTested under rigorous temperature conditions
Inertial Measurement UnitHoneywell acquired Drapers Tuning Fork technologiesReplaced Ring Laser Gyro in original designDeveloped a low-cost, micro-device capable of accurately measuring rates and displacements
Munitions ControlsDraper Laboratories working with Office of Naval Research to develop countermeasure-proof munitionsTuning Fork Gyroscope used for positioning and rates of displacementGyro allows for inertial movement, bypassing countermeasures
Gait-Phase Detection sensor Embedded in a Shoe Insole Measures the angular velocity of the footUsed to activate a functional electrical stimulator attached to the foot.Over 96% accuracy
Conclusion