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EECS 373 Gyroscopes Kevin Chyn Scott Perry Brian Schlenker

EECS 373 Gyroscopes Kevin Chyn Scott Perry Brian Schlenker. http://embeddedsystemnews.com/stmicroelectronics-introduces-a-new-family-of-single-and-multi-axis-mems-micro-electro-mechanical-systems-gyroscopes.html. Outline. Introduction to Gyroscopes Theory of operation Applications

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EECS 373 Gyroscopes Kevin Chyn Scott Perry Brian Schlenker

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  1. EECS 373 Gyroscopes Kevin Chyn Scott Perry Brian Schlenker http://embeddedsystemnews.com/stmicroelectronics-introduces-a-new-family-of-single-and-multi-axis-mems-micro-electro-mechanical-systems-gyroscopes.html

  2. Outline • Introduction to Gyroscopes • Theory of operation • Applications • Historic and Modern Varieties • History of gyroscopes • Current technology • Implementation • Algorithms • Feedback and control

  3. What is a Gyroscope? • Device used to measure or maintain orientation • Works on the principals of angular momentum • Initial axis of rotation is conserved • Consists of a spinning mass on an axel

  4. How Gyroscopes Work • Mechanical Gyroscope • Spinning mass mounted on gimbals • Free-output vs. Fixed-output • Sensors on axis to detect rotation • Procession • Electronic Gyroscope • Coriolis vibratory gyroscope • Proof mass fed oscillating current to induce vibrations • Vibrating mass tends to oscillate in initial plane of reference • When rotated, oscillations in orthogonal plane detected by circuitry

  5. Common Uses • Gyrocompass • Used by ships to find true north • Seeks minimum potential energy • Stability Assistance • Hubble Space Telescope • Bicycles • Inertial Guidance System • Guided Missiles • Measure angular velocity in inertial reference frame • Detect changes to orientation • Combined with accelerometer for 6 axis sensor

  6. Consumer Electronics • Wii Remote • Tilt, yaw, pitch • Rate of angular movement • Smart Phones • Screen Orientation • Gaming Input • Laptops • Free fall detection

  7. History of Gyroscopes • Initially a toy, not a tool • Tops were common in ancient civilizations • Began to be used in naval navigation and science during the 18th and 19th centuries 1852 French gyroscope used to measure Earth’s rotation 1860 gyro used to model orbital motion

  8. History of Gyroscopes • Integration with electronics • In the early 20th century, gyroscopes became combine with electric motors, allowing them to operate without mechanical power • Miniaturized during WWII for torpedo, ship, and plane navigation • Further miniaturized with the advent for silicon-based electronics WWII era bomb release control mechanism Common $50 consumer gyroscope available on Sparkfun

  9. Types of Gyroscopes • Rotary gyroscope • Rotor suspended in a gambol spins independently in order to conserve angular momentum • Mostly unused in modern systems • Fiber optic gyroscope (FOG) • Fiber optic coil determines changes in orientation by path of light in the coil • Beam traveling against rotation has slightly shorter path • Microelectromechanical systems (MEMS) • Uses very small vibrating mechanism to detect changes • London moment •  Spinning superconductor generates a magnetic field • Extremely accurate tool or modern science

  10. Common Gyroscope Criteria • Performance • Measurement range • Number of sensing axes • Nonlinearity • Bandwidth • Angular Random Walk (ARW) • Bias • Bias Drift • Bias Instability • Specifications • Cost • Working temperature range • Shock survivability • Size/Mass

  11. Angular Random Walk

  12. Examination of Recent Gyros

  13. General Algorithms • Noise reduction via low pass filter • Scale calibration to get meaning from gyroscope data • Integrate data over time to get “absolute angle” • Enhancement using Kalman filter • Can reduce/eliminate integration drift

  14. Inertial Navigation Systems • Dead reckoning – using previous position to determine current position • Used on ships, aircraft, submarines, missiles, spacecraft, etc • Firefighters/military – step based INS

  15. GPS/INS GPS INS • Low refresh rate • 10Hz? 20Hz? • Relatively low resolution • Location to n meters • Limited to outdoors • High refresh rate • Kilohertz • Relatively high resolution • But prone to drift • Doesn’t rely on satellites Combine both sensors using Kalman Filter to produce highly accurate results

  16. Feedback Control Systems Optical Image Stabilization • Vibration detected using gyroscopes • Movements modeled as sinusoid • Lens is shifted to counteract vibration

  17. Refrences • http://physics.kenyon.edu/EarlyApparatus/Mechanics/Gyroscope/Gyroscope.html • http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=327 • http://orgs.usd.edu/nmm/News/Newsletter/August2010/ConnResearch.html • http://www.sensorwiki.org/doku.php/sensors/gyroscope

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