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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 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 • Historic and Modern Varieties • History of gyroscopes • Current technology • Implementation • Algorithms • Feedback and control
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
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
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
Consumer Electronics • Wii Remote • Tilt, yaw, pitch • Rate of angular movement • Smart Phones • Screen Orientation • Gaming Input • Laptops • Free fall detection
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
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
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
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
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
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
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
Feedback Control Systems Optical Image Stabilization • Vibration detected using gyroscopes • Movements modeled as sinusoid • Lens is shifted to counteract vibration
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