ECE5320 Mechatronics
Assignment#01: Literature Survey on Sensors and Actuators
Topic: Rotary Voice Coil Actuator
Prepared by:
Karl Burk
Dept. of Electrical and Computer Engineering
Utah State University
(435)752-0619 (ECE Dept.)
karlburk@cc.usu.edu
3/10/2006
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
– Other Relevant issues in applications (such as, how
to choose, cost information, where to buy etc.)
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-3
Reference list
1. Voice-Coil Actuators, Designfax, September 1989
(with Joe Stupak).
2. Voice-Coil Actuators: Insight into the Design, PCIM
1989 conference, Long Beach, CA, October 1989 (with
Joe Stupak).
3. IMAPS Device Packaging Conference
March 13 - 16, 2005
4. Where do voice-coil actuators fit in?, Joe Campbell
BEI Kimco, 8/8/2003, Penton Media
5. Electromechanical Actuators, 6th edition, GEEPLUS
Europe Ltd
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-4
Reference list
1. Shorted Turn Effects in Rotary Voice coil Actuators,
Michael A. Moser, Quantum Corporation, Milpitas,
CA, USA
2. Noise Reduction Using Dampening in Voice Coil
Motors/Actuators of Hard Disk Drives, Walker C.
Blount, Sr. Engineer, copyright International Business
Machines Corporation 2001, October 2001
3. High performance laser shutter using a hard disk drive
voice-coil actuator, L. P. Maguire, S. Szilagyi, and R.
E. Scholten, Review of Scientific Instruments, Volume
75, Number 9, September 2004
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-5
To explore further
(survival pointers of web references etc.)
• http://yuan.ecom.cmu.edu/rotaryvoicecoil/
• http://www.consult-
g2.com/course/chapter11/chapter.html
• http://www.epanorama.net/circuits/diskstepper.html
• http://ieeexplore.ieee.org/iel4/1037/7500/00697558.pdf?
arnumber=697558
• http://www.beikimco.com/products/rotaryvoicecoil.php
• http://www.beikimco.com/products/presentations/actuato
rs.php?n=01
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-6
To explore further
(survival pointers of web references etc.)
• http://www.beikimco.com/products/beiactuatorsiz
ingprogram.xls
• http://www.rohm.com/products/shortform/06cam
era/camera_index1a.html
• http://www.machinedesign.com/ASP/strArticleID
/56123/strSite/MDSite/viewSelectedArticle.asp
• http://www.geeplus.biz/vcm.pdf
• http://www.agere.com/storage/storage_disk_drive
.html
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-7
Major applications
Rotary voice coil actuators (also called voice coil motors,
moving coil actuator, limited angle torquers, sector torquers, or
swing-arm actuators) are useful for several applications including:
• Hard disk drive head positioning
• Integrated circuit manufacturing processes
• Digital camera and focused light beam
shutter and anti-shock systems
• Beam steering applications
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-8
Difference from linear voice coils
• Rotary voice coils are different from linear
voice coils:
– Linear voice coils will often have their magnetic field oriented
in a straight line along the direction of travel of the moving part
although other models are also designed with flat coils.
– Linear voice coils are used more for positioning when fast or
precise positioning along a straight path is desired and are often
used orthogonally in conjunction with other linear voice coils
to achieve x-y or even x-y-z positioning.
– Rotary voice coils may not be able to boast of linear motion,
but they can take advantage of principles of leverage to achieve
possibly greater speed or precision.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-9
Basic working principle illustrated
• If there is an electric current through a coil of wire in a magnetic
field, then a translational force is incurred between the magnetic
field and the wire in the direction indicated by the right hand rule.
• The force will be directly
to the amount of current passing
through the wire.
• This can allow a force in
either direction depending on
the direction of current flow.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-10
Basic working principle illustrated
(continued)
• Some may have magnetic fields oriented radially
and others axially (flat configuration) depending
upon the design.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-11
A typical sample
configuration in application
• A hard disk drive head actuator is a common
application.
• The rotary voice coil is used to position the heads
of a disk drive at a precise position for reading
and writing of data.
• Fine position tuning is accomplished by a closed
loop feedback system which often feeds back
positioning information read from the disk itself.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-12
Applications: Hard disk drive head actuator
• Solenoid is used for
parking the heads when the
drive is not in use since a
voice coil has no ‘natural
position’ it returns to when
not being used.
• Appropriate shielding
must be used when it is
near a magnetic data
storage disk.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-13
Applications: Hard disk drive head actuator
Rotary voice coils can be very fast and have a
resolution not limited by the actuator itself. . .
(Click picture to start video)
Entire video clip can be found at:
http://www.digg.com/movies/Video:_Inside_of_a_Hard_Drive_(direct_link)
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-14
Applications: Focused light beam shutters8
• It has been shown that a typical hard drive voice
coil actuator can be used to operate a shutter at
high speeds:
– Shutter speeds reported faster than
10 mm/ms. (allows focused beam
switching in under 10 μs)
– Aperture size is up to 32 mm.
– Can be switched at regular
intervals with a sinusoidal signal.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-15
Applications: Beam steering applications5
• An x-y tilting motor uses a set of independently
controlled, flat voice coil actuators.
• When coils are energized in opposing
directions, the center module can be
turned (tilted).
• Some models, when the coils are
energized in the same direction, the
center module can be moved linearly. (Some modules do
not allow for linear movement.)
• A mirror is often attached to the center module which is
used for the beam steering.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-16
Major specifications4
• Specifications vary by design and application
• Torque generated: Up to 120 N-m
• Typical total strokes: Up to 120°
• Typical Accelerations: An order of magnitude
higher than typical motor technologies
• Maximum speed: Limited only by guidance
system. Higher speeds are possible in short-stroke
applications using flexible membranes instead of
bearings.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-17
Design considerations and goals
• Coils must withstand a lot of thermal cycling.
– Copper wire undergoes less thermal expansion than aluminum.
• Coils must be electromagnetically efficient.
– Wire should be wrapped tightly. (Square wire gives greater
packing factor.)
– Design to use shielding appropriately and inhibit eddy-currents.
• Friction must be kept at a minimum.
– Dimensions should be precise and bearings or flexible
membranes as appropriate.
• Positioning should employ accurate sensing and
feedback.
– Methods may vary by application (encoders, rotational
accelerometers, etc.).
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-18
Design considerations and goals
(continued)
• Design should entail appropriate mass distribution.
– For high speed the moving part should be well balanced and
have its mass distributed more proximally to the rotational axis
(low rotational inertia).
• Effective current control is vital to accurate positioning.
– Noise reduction methods should be employed where needed.
• Electrical termination should be built to handle stress.
– Often flexible cabling is used and secured at places in addition
to the solder joints.5
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-19
Strengths and advantages
• Generally have short rise and settling times (on
the order of milliseconds)
• Usually two-wire input (non-commutated)
• Cog free
• Virtually hysteresis free
– (typically <<1% of developed force)5
• No inherent preferred position
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-20
Limitations
• Effective for relatively short distance movement
• Limited output force
• No inherent preferred position (can be a
limitation)
• Must have a servo drive (or other current control
device) and usually a position feedback system
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-21
Other relevant issues in applications
• Noise reduction in hard drives is an issue that has
brought about several proposed solutions:
– Shorted turns have successfully been used in hard drives, but they can
reduce seek times.6
– More advanced bearings have
helped to reduce vibrational
noise.7
– VCM damper pads cushion
to reduce actuator noise.7
– Secondary micro-actuators
might be employed if they
prove their value by their
performance.7
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-22
Other relevant issues in applications
(continued)
• Control of rotary voice coil actuators is often
performed by specialized integrated circuits.
• These integrated circuits typically perform
and coordinate several additional hard drive operations
simultaneously.
11/22/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators