ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Voice Coil Actuators

1. Prepared by: James Withy Utah State University E: jamesw@cc.usu.edu ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Voice Coil Actuators 3/11/2005

2. Slide-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.) 03/11/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Slide-3 Reference list • Ariex Corporation • http://www.airex.com/products/voice.htm • Magnetic Sensors Corporation • http://www.magsensors.com/ • H2W Technologies, Inc. • http://www.h2wtech.com/noncommdcactu.htm • MIT Media Research Lab • http://robotic.media.mit.edu/projects/novelActuator.html 03/11/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. References (continued) • BEI Technologies, Inc. • http://www.beikimco.com/products/vca.php • R Thibedeau; Tutorial on the Rotary or Swing Arm Voice Coil Actuator Used on Modern Hard Disk Drives • http://drachma.ecom.cmu.edu/rotaryvoicecoil/ • J Lieberman; Voice Coil Actuator Array • http://bea.st/sight/array/

5. References (continued) • Servo Magnetics, Inc. • http://www.servomag.com/lin/linear.htm#moving_coil • Heason Technologies Group • http://www.heason.com/products/linear_motors/linear_motors_1001942168/linear_motors_1001942168.html • PC Guide • http://www.pcguide.com/ref/hdd/op/actActuator-c.html

6. Slide-6 To explore further (survival pointers of web references etc) • BEI, Kimco Magnetics Division • Good all around source for information and products • http://www.beikimco.com/products/vca.php • Heason Technologies Group • Good source for new developments in voice coil technology • http://www.heason.com/products/linear_motors/linear_motors_1001942168/linear_motors_1001942168.html • H2W Technologies • http://www.h2wtech.com/noncommdcactu.htm 03/11/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Slide-7 Major applications • Used in situations where small size is required of linear or rotary actuation • Used where infinite position sensitivity is required • Gives smooth force vs. stroke curves • High speed, closed-loop servo control • Small precision movements • Constant force regardless of actuator position • No eddy currents, good for high frequency (think speaker type movement) 03/11/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Major Applications (cont’d) • What can you do with a voice coil actuator? • Nothing! • Voice coil actuators are servo components • You need: • The muscle: the voice coil actuator • The eyes: the position feedback sensor • The brain: the servo drive • It is not a solenoid! (BEI Technology)

9. Most Common Use • Hard Drives – Rotary actuator moves the hard drive heads in a closed control loop • Laser Beams – Arrays of four linear actuators are used for high precision positioning of the laser beam mirror • Medical Apparatus – Used in respiration devices

10. Basic Working Principle • “Voice coil actuators are single-phase, two wire non-commutated direct-drive, hysteresis-free, cog-free devices used for providing highly accurate linear motion. They are limited-motion devices that use a permanent-magnetic field and coil to produce a force proportional to the current applied to the coil.”

11. Basic Principle (continued) • In its simplest form, a linear voice coil consists of a tubular coil of wire within a radially oriented magnetic field. Permanent magnets lining the inside diameter of a ferromagnetic cylinder produce the field. The magnets are arranged so the sides "facing" the coil are the same polarity. The core of ferromagnetic material completes the magnetic circuit. It sits on the coil's axial centerline and is connected on one end to the permanent magnet. When current flows through the coil, it generates an axial force on the coil and produces relative motion between the field assembly and coil (Servo Magnetics, Inc.).” • See http://www.servomag.com/linear_actuators.html for a demonstration

12. Characteristic Packages (Heason Technologies Group) Linear Actuator Many different sizes and custom designs available Rotary Actuator (think Hard Drive)

13. Typical Sample Configuration • Laser beam positioning system (Heason Technology Group)

14. Typical Rotary Configuration (PC Guide.com)

15. Major Specifications • Force rating (peak and continuous) – .3 - 5000 N • Stroke Range -- .04 IN – 2 IN • DC Resistance – 2-20 Ohms • Force Sensitivity -- .7 – 130 N/Amp • Package Size – Varies and customizable • Operating Temp. -- @ 25 Deg. C, 155 Dec C. coil

16. Sample Spec Chart

17. Limitations • Short displacements and relatively small force output limits applications • Fixed radial motion may inhibit cylindrical actuators • Must have supporting control circuitry in a closed loop to use voice coils

18. How to Choose an Actuator • Major factors to consider: • Available sensor volume in final installation • Force/Torque required • Linear vs. Rotary action considerations • Current draw and power requirements • Speed response

19. Companies Include: Airex Corp. Custom Designs H2W Technologies Standard Product Line BEI Tech, Inc. Standard Product Line Custom Design Servo Magnetics, Inc. Standard Product Line Heason Technology Group Standard Product Line Custom Design Densitron Control Sys. Custom Design Where to Buy

20. Cost Information • Cost ranges from tens to hundreds of dollars for standard product line units • Custom and prototype designs start in the hundreds and go up from there for development costs

21. Interesting Projects • Use of voice coil actuators in robotic movement for MIT’s Media Research Lab

22. MIT Robot Actuation • “The goal of this project is to create voice coil-type electromagnetic actuators, with integrated position, velocity and force sensing means. Voice coils are silent, have only one moving part, are naturally smooth and linear, are very robust, have reasonable force and power densities, and are relatively inexpensive (MIT).”