ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Fiber Optic Gyro

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Fiber Optic Gyro Prepared by: Jeff Ferrin Dept. of Electrical and Computer Engineering Utah State University 3/10/2006

2. Outline • Reference list • To probe further • Major applications • Basic working principle illustrated • A typical sample configuration in application (application notes) • Major specifications • Limitations • And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • Northrop Grumman Navigation Systems Division • KVH • Prentice Hall PTR. • Wikimedia Foundation, Inc. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To explore further (survival pointers of web references etc) • www.kvh.com • http://www.nsd.es.northropgrumman.com/Html/FOG_Tech/# • http://en.wikipedia.org/wiki/Sagnac_effect ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Major applications • Inertial Measurement • Navigation • Aircraft • Spacecraft • Used for dead reckoning • Stabilization • Military turret stabilization • Motion Sensing • Unmanned Vehicles ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Applications of FOG • Autonomous Vehicles Used for angular position feedback and heading. Autonomous Solutions Inc. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Fiber Optic Gyroscope • Fiber optic gyros are making mechanical gyroscopes obsolete • The theory behind the fiber optic gyro has been around for decades • The accuracy and repeatability are being improved each year • The FOGs are becoming smaller and the costs continue to be driven down ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. How does a FOG work? www.kvh.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. How does a FOG work? • The theory is based on the Sagnac effect. • A beam of light is split and each half travels the same path but in opposite directions. Northrop Grumman ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. How does a FOG work? • Light traveling in the direction of rotation • This half of the light is “chasing” the end of the coil because the coil is moving away from the light • This increases the distance the light has to travel which will also increase the time required to reach the end of the path ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. How does a FOG work? • Light traveling in the opposite direction of the angular rotation • This half of the light is moving towards the end while the end is moving towards the light • This results in a shorter distance for the light to travel which will reduce the time. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. How does a FOG work? • After completing the path of the fiber-optic cables the waves will be out of phase • The angular rate is determined from this phase shift ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. How does a FOG work? • Output signals for no rotation • Phase angle between the two waves is 0 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. How does a FOG work? • Output signals for an angular rotation • Phase angle between the two waves is 0 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. How does a FOG work? • For any given change in angular velocity the phase of the two light waves will change continuously • This change in phase is converted to an angular rate • This angular rate can be integrated to obtain the position of the FOG ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. FOG • A longer fiber-optic path means that the waves will be further out of phase • The resolution of a fiber-optic gyro can be increased by increasing the length of the fiber-optic path • With a longer path, even small angular rates will be detected because of the fact that the time for the light waves to get out phase increases • Fiber-optic cords up to 5 km (Transducers and Their Elements, Prentice Hall PTR) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Advantages • Faster response than mechanical gyroscopes • Rugged and durable • No moving parts • Accuracy can reach 0.001 deg/hr • High tolerance for shock and vibration ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Advantages • Not sensitive to gravity like mechanical gyroscopes • High reliability ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Disadvantages • Larger than mechanical gyros but the size is continually getting smaller • A bias drift over time • High costs ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Summary • Fiber optic gyros are replacing the older mechanical gyroscopes • The fiber optic gyro is based on the Sagnac effect • The performance is rapidly increasing ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

21. Manufacturers of FOGs • KVH • The leader in the technology of this field • Crossbow ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators