A hard disk voice coil assembly, also called actuator, is a linear control device within a hard drive responsible for positioning the read write heads. Linear voice coil motors with internal bearing pwrcon. The question is how is the voice coil controlled, using a scope on an old drive you can see there is obviously ac present, so i put a circuit togther that reverses the polarity acrross the coil controlled by a pwm output from a pic, it works but the coil gets to its full movement within a small deviation from 50% symmetry, and its just as good. The optimized design of a voice coil motor was performed, which can be used as an actuator for the active vibration isolation system. Allegro microsystems 955 perimeter road manchester, nh 031033353 u. To be precise, it pushes or pulls on the mass, the mass then moves as a result of this force. The ventilated voice coil gap keeps the temperature of the voice coil low and stable for increased power handling and reliability.
Inverting the current direction inverts the force direction. Custom voice coils have been the core of our business at precision econowind since we began producing electric coils over 40 years ago. The vcm module provides the autofocus and image stabilization capability of the ccm. Such hard drive will probably be hard to fine, the diy is probably the best option to make the ideal forcestroke at a low price. Test bench is an open forum for oem driver manufacturers in the loudspeaker industry and all oems are invited to submit samples to voice.
As such, it has a complex structure with multiple pieces that flex and. Application of voice coil motors in active dynamic vibration absorbers. Voice coil, the periodical for the loudspeaker industry is free for those who qualify. The voice coil is the motor part of the servo system that positions the heads. Optimal control design of a voice coil head actuator in a. These motors, having a large axial hole throughout the entire coil and body structure are ideal for optical focusing, scanning and other precision positioning applications requiring an axial opening through the motor. The device contains a selectable transconductance loop, which allows high precision for head positioning. The dac is controlled via a i2c serial interface that operates dac by clock rates up to 400khz.
When current is applied to the coil, a force is generated in direct proportion to the amount of current. Just a prototype, and at the beginning a unique voice coil motor would be fine, to setup and refine parameters. Voice coil motors vcm voice coil actuators stanford. It is sometimes said that voice coils are intended for fast. Moving magnet voice coil actuators it have the coil attached to a stationary soft magnetic housing, which also serves as a conductor of the magnetic flux. Cn3927 low voltage voice coil motor driver with i2c interface. The voice coil driver l6246 is a linear power amplifier designed to drive single phase bipolar dc motors for hard disk drive applications. Voice coil modules atb automation mechanics motion. Applying a voltage across the terminals of the motor causes the motor to move to one direction.
Decrease timetomarket with celera motion precision components and mechatronic assemblies, combined with extensive design, integration, and fabrication expertise delivering optimal solutions for the most demanding applications. Coupling the rotary voice coil actuator to your bearing system and a rotary encoder or other feedback device yields a system that is capable of intricate angular position, velocity, and acceleration control. Voice coil magazine 2010 april issue audio components. Voice coil actuation exploits the interaction between a currentcarrying coil winding and the field generated by a permanent magnet. The key element is the voice coil motor that we extracted from a regular hard disk drive a 3. Bidirectional actuators can be realized, rotatory as well as linear. Design, fabrication and control of microactuators for. Round, rectangular, dshaped, flat wire or custom shaped coils can be produced using precision layering practices. Voice coil impedance as a function of frequency and.
Optical image stabilization ois stmicroelectronics. Especially developed for high precision applications with high oscillation frequencies. A voice coil actuator controls the movement of the readwrite head following the principle of electromagnetic attraction and repulsion. Some vcm modules require more than 12 dispense points. Voice coil motors can be controller by s300 and s700 servo amplifiers, see. Linear dc motors, voice coil motors vcm or voice coil actuators vca are the simplest type of electric motors.
The arm over an hdds disk has three primary stages. The voice coil diameter for the c8sw, c10sw, c12sw subwoofers is 51mm 2inch and 75mm 3inch for the c15sw, allowing for elevated power handling, dissipation of heat thereby lowering power compression, and maximizing the size of the magnet around the voice coil for enhanced motor compliance. It consists of a copper coil wound around a former and a permanent magnet. The subwoofers have been designed to work in very compact volumes while having a very high spl and an amazing energy. Considering the above tradeoffs, a voice coil actuator was selected for the linear motor.
Abstractthis research designs and fabricates a voice coil motor with shorted turn for positioning control experiment and uses laser displacement sensor to measure the displacement. Slidingmodebased fuzzy control is developed to carry out positioning. Designed for linear control of voice coil motors, the cn3927 is capable of operating voltage from 2. The amplitude of the frequency determines the displacement of the voice coil motor. The direction of movement is determined by the direction of current flow in the the single phase linear voice coil actuator allows direct, cog. In a conventional disk drive, the voicecoil motor performs all positioning of the head, swinging it back and forth across the disk. Our encoders, motors, servo drives, air bearing spindles, and mechatronic subsystems enable engineers to solve. Voice coil motors are highly controllable electrical actuators suitable for applications needing only limited displacement. The term voice coil comes from one of the first applications. The power stage is composed of 2 power amplifiers, in ab class, with 4 dmoss, with rdson of. The voice coil actuator would be the spool for modulating the valve orifice area. Careful engineering of the entire motor structure and suspension system voice coil, magnet, surround and spider is required maintain a high level of. A voicecoil motor is designed and optimized as the active control actuator to provide proper.
Designed for linear control of small form factor voice coil motors, the a3907 is capable of peak output currents to 102 ma and operating voltages to 5. This optimized vcm can easily be implemented to control the low frequency vibration typically within the range 0. The magnets position, the type of magnet, the surrounding structure, etc. I am able to drive a lvcm02503801 linear voice coil using a cytron 10a motor driver shield and a spwm sinewave pwm signal but when i add an rc filter i get response in the motor. Voice coil and motor system the voice coil used in the unity midbass is a 2layer aluminized copper wire coils on a round former. Characteristics and selection of voice coil motors. Internal circuit protection includes thermal shutdown with hysteresis, flyback clamp diode, and undervoltage monitoring. Pdf application of voice coil motors in active dynamic. Rotary voice coil actuators are supplied unhoused without bearings. Result of the optimization was verified using fem simulation. The eblock lies between the vcm and the suspension and contains the pivot point.
Compact single phase miniature voice coil modules with guide, driven by single fase avm voice coil linear motor. The si9961a is a linear actuator voice coil motor driver suitable for use in disk drive head positioning systems. The coil wrapped around the trapezoidal voice coil is attracted to the magnets within. A voice coil is a linear actuator, that moves a mass along a line. Motor type pimag voice coil drive magnet material ndfeb n38sh coil resistance 8. The kit allows users to take advantage of the inherent benefits. Driving a linear voice coil motor arduino forum index. Applying a voltage to the device actuates the coils, which rotates the arm.
In the motor parts menu also located on the right side of the main menu in fig. The si9961a contains all of the power and control circuitry necessary to drive the vcm that is typically found in 31 2 inch hard disk drives and optical disk drives. The voice coil motor will oscillate at the desired frequency and displacement. Low voltage voice coil motor driver allegro microsystems. Voice coil motor vcm, also called voice coil actuators vca, is an electric motor consists of a magnet and yoke in conjunction with a coil. From model and simulation to automotive application. It would be built with inexpensive, commercially available components magnet, voice coil, suspension from the loudspeaker industry. In this application, a very lightweight coil of wires is mounted within a strong magnetic field produced by permanent rareearth magnets.
We offer many options including sizes, ohm load, former materials and wire types. Please contact us anytime for questions or more information. In recent years, the most common application for voice coils has been to move the heads inside computer disk drives, but theyre also widely found in medical devices, mirror controls, and oscillating systems. Thus a voice coil does not primarily move the mass, motion is the consequence of the force it applies to it. Precision motion control solutions celera motion, a. Also like the paper cone versions, this driver has a gap height of 20mm and voice coil length of 8mm of the graph. Linear voice coil motors actuators and micro voice coil. Trapezoidal voice coil, 3 actuator axis, 4 arm, 5 disk head, 6 drive motor, and 7 discs or platters.
Voicecoil motor varedan technologies technical staffy abstractthis application note provides a design process for sizing linear and pwm ampli. The voice coil actuator vca developers kit from bei kimco is a completely selfcontained kit including a vca with builtin feedback sensor and a programmable controller with motion control software that runs on the users local pc. Design inputs consist of the motor force constant, backemf constant, coil resistance and inductance, load inertia, and worstcase velocity and load force pro. In particular, it is commonly used to refer to the coil of wire that moves the readwrite heads in a movinghead disk drive. Advanced power electronics center department of electrical and control engineering national chiao tung university, taiwan. Abstractthis research designs and fabricates a voice coil. Positioning control of voice coil motor with shorted turn. Moving coil, voice coil actuators it consists of the usually stationary field magnet assembly and the moving coil assembly. This force causes the moving part which can be either the magnet or the coil to travel. Voice coil actuators are single phase motors which can be controller like a dc motor. Voice coil impedance as a function of frequency and displacement mark dodd1, wolfgang klippel2, and jack ocleebrown.
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