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

1

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

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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