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Prepared by: Andrew Hall Dept. of Electrical and Computer Engineering Utah State University

ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Micro Electro-Mechanical Systems (MEMS) sensors. Prepared by: Andrew Hall Dept. of Electrical and Computer Engineering Utah State University E: a.hall@aggiemail.usu.edu. 3/6/2009. Outline.

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Prepared by: Andrew Hall Dept. of Electrical and Computer Engineering Utah State University

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  1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Micro Electro-Mechanical Systems (MEMS) sensors Prepared by: Andrew Hall Dept. of Electrical and Computer Engineering Utah State University E: a.hall@aggiemail.usu.edu 3/6/2009

  2. Outline • Reference list • Overview • Major applications • Basic working principle illustrated • Applications using MEMS • Major specifications • Limitations • MEMS sensors manufacturers ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  3. Reference list • Roos, Gina, ‘MEMS sensors: good medicine’, www.eetimes.com/news/design/showArticle.jhtml?articleID=205207022 • Torrance, Randy, ‘MEMS-based inertial sensor is not your grandfather’s gyroscope’, EDN, 12/1/2008 • Weinberg, Harvey, ‘MEMS (Micro Electro-Mechanical Systems) Technology, http://www.sensorland.com/HowPage023.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  4. To explore further (survival pointers of web references etc) • http://www.sensorland.com/HowPage023.html • Sensorland provides information on how the MEMS sensor works and how it has moved into common products. • http://www.sensorsmag.com/articles/0203/14/ • Sensorsmag provides more information MEMS and other sensors. • http://en.wikipedia.org/wiki/MEMS • Basic information on MEMS. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  5. Overview • MEMS sensors are one of the smallest mass-produced, low g, low cost, dual axis accelerometers. • Two major uses of MEMS sensors: • Accelerometers • Gyroscopes ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  6. Overview - Accelerometer • Acceleration causes deflection of the body of the sensor (proof mass) from its suspended centre location. • The proof mass is suspended by polysilicon springs above the substrate such that the MEMS structure can move in the X and Y axes. Picture from: http://www.sensorland.com/HowPage023.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  7. Overview - Gyroscope • MEMS gyroscopes use a vibrating structure to determine orientation instead of traditional rotating disk. • Using Coriolis acceleration the gyroscopes measure their angular rate. Picture from: www.edn.com/article/CA6614434.html?title=Article&spacedesc=news&nid=3927 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  8. Major Applications • Accelerometers in consumer electronics: • Cell phones • PC hard disk drives • Cameras • Computer peripherals • Wireless devices • Airbag systems ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  9. Major Applications • Gyroscopes in: • Cars • Robotics • Computer peripherals • Wireless devices • Other applications requiring yaw detection. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  10. Major Advantages • Small footprint • Mass producible • Sensitive to low g’s • Low Cost • Low Power • High Performance • Integration • Rugged ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  11. Principle - Accelerometer • Proof mass has 32 sets of radial fingers that make up a capacitor with a pair of fixed plates. • Differential capacitance is measured from the fingers and plates using synchronous modulation/ demodulation techniques. Picture from: http://www.sensorland.com/HowPage023.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  12. Principle - Accelerometer • ADXL202 MEMS sensor block diagram is shown. • Pulse-width-modulation (PWM) proportional to acceleration is the output of this MEMS accelerometer. • A microcontroller is used to decode the PWM. Picture from: http://www.sensorland.com/HowPage023.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  13. Principle - Gyroscope • Image taken of a gyroscope MEMS from a camera shows how the gyroscope was similar to the accelerometer in basics. Image from: http://www.edn.com/article/CA6614434.html?title=Article&spacedesc=news&nid=3927 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  14. Principle - Gyroscope • Vibrating structure is used instead of a traditional rotating disks to determine orientation. • Acceleration proportional to the object’s distance from the center of the disk known as the Coriolis acceleration is the principle behind MEMS sensor gyroscopes. • Gyroscope has two MEMS devices similar to accelerometer in them. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  15. Principle - Gyroscope • Orientation of two MEMS structures allows two-axis detection and improved Coriolis acceleration measurements. • MEMS device shown has onboard EEPROM for factory calibration eliminating the need for external end-user calibration. • External circuitry is needed to detect the capacitance changes and regulate the MEMS sensor outputs. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  16. Devices Using MEMS sensors “Suitable for oxygen concentrators, inhaled anesthetics and ventilators, Omron's D6F MEMS flow sensors can measure flow speed from 1 mm/s to 40 m/s.” “ADI's two-axis accelerometer is used for tilt inclination measurement of the user's forearm in Omron's blood pressure monitor for the wrist.” Images from: www.eetimes.com/news/design/showArticle.jhtml?articleID=205207022 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  17. Major Specifications • Sensitivity • Accuracy • Voltage • Designed measurement parameters • Response time • Temperature range of operation • IC package ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  18. Limitations • Mechanical design of microscopic mechanical systems take time to understand. • Materials not well characterized mechanically. • Polysilicon’s mechanical properties have had little mechanical understanding and change properties in the microscopic world. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  19. Limitations • Electronic design of MEMS sensors is very challenging. • Electronics have to be small to save on cost. • Be able to realize small variable capacitance and convert them to the proper sensing. • Have to compensate for temperature and noise. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  20. MEMS Sensor Manufacturers • Freescale Semiconductors • Analog Devices • STMicroelectronics • Texas Instruments • IBM • Qualcomm • VTI Technologies ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

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