Voice Coil Motors (VCM) / Voice Coil Actuators

The Dura Magnetics Value:

Supply magnets for existing Voice Coil Motors designs (Rare Earth Neo and Samarium Cobalt)
Design magnets for custom Voice Coil Motors
Design Voice Coil Motors for application specific projects
Manufacture Custom Voice Coil Motors

While the coil specifications are important to the VCM design and are included in any Boundary or Finite Analysis simulations, Dura Magnetics does not design nor supply coils and bobbins.

Description:

Voice Coil Motors (VCM), also called Voice Coil Actuators (VCA), are a very mature design that utilizes a magnet and yoke in conjunction with a coil. The coil and magnet are concentric about a common axis and there exists an engineered magnetic return path.

The coil is typically connected to a mechanism which translates the coil’s linear motion into a beneficial action. For example, a conventional loud-speaker uses a voice coil motor to drive a cone which converts the coil’s oscillating motion into sound energy.

The typical characteristics of a voice coil motor are a round coil, concentric with and located in a gap where a radial magnetic field is present. This field is generally developed by a permanent magnet located within the structure. The interaction between the coil’s magnetic field and the magnetic field in the gap is what gives rise to the linear force acting on the coil. (The coil’s magnetic field is due to the current flowing in coil.) The magnet’s position within the unit, the type of magnet, the surrounding structure, etc., can influence the nomenclature of the unit.

Originally, most VCMs were similar to a loud-speaker’s design. This design uses a gap whose axial length is short and the magnetic field density in the gap is very high. Because of the short gap length, this style required a longer axial length coil to create any reasonable “stroke” or axial travel. Newer designs utilized longer axial length gaps, lower magnetic field densities, and shorter coils using fewer turns of wire. This means that more of the coil operated in the gap, resulting in a mass and resistance reduction. Lower mass equals better acceleration and “settling” and lower resistance translates into greater linearity.

When a VCM / Actuator is coupled with an appropriate feedback device, amp, and controller, precise position, velocity, and acceleration control is possible. When a VCM is used in this geometry it is often referred to as a Positioning Stage or VCM Linear Stage.

Key Benefits of a VCM – Voice Coil Actuator:

No commutation required
Low to no hysteresis
Zero cogging
Fewer mechanical components compared to “screw-type” actuators
Linear control characteristics
High power to mass ratio
High power to volume ratio
Infinite position (Limited only by the encoder device.)
High acceleration

Uses:

Where precision linear movement is required
Where precision force is required
Where oscillatory motion is required
Where Dynamic Movement is required

Example Applications:

Shakers – Vibrators
Lens focusing
Servo valves
Positioning Stages
Speakers

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