Gyroscope (1)

8/2/2019 Gyroscope (1)

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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

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Gyroscope (1)