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# Voice Coil Actuators

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H2W Technologies Voice Coils are ideal for short stroke (typically less than 2 inches) closed loop servo applications. Their compact size allows them to fit into small spaces. They have very low electrical and mechanical time constants. The low moving mass allows for high accelerations of light payloads.

These actuators are wound in such a way that no commutation is required for motion to occur. The result is a much simpler and more reliable system.

Coupling the actuators with a bearing system (if not supplied), position feedback device, linear servo amplifier and motion controller yields a system that is capable of intricate position, velocity, and acceleration control. These actuators can also be used for precise force control because of the linear force versus current characteristics.

Voice Coils operate on the principal of the Lorentz force equation:

$$Force = B \times I$$
B = Flux density (Tesla)
I = Current (Amps)

Simply stated, a current carrying conductor placed in a magnetic field will have a force exerted upon it. This force is proportional to the direction and magnitude of the current and the flux density field. Since the permanent magnet flux density field is fixed, the direction of the linear displacement depends on the polarity of input current. The amount of force that is produced is directly proportional to the magnitude of the input current.

Our voice coil actuators are available in both standard as well as custom sizes. You can choose from either the moving magnet (NCM type) or moving coil type (NCC Type):

• The moving coil actuators, NCC Type (sometimes referred to as voice coils) are typically supplied without bearings or a shaft, but can be added if desired. They are generally larger in diameter and shorter in length. Higher forces can be achieved by increasing the diameter. This type of actuator can be designed with large radial clearances to ensure no contact between the coil and magnet assembly if a tilt or radial movement is required.
• The moving magnet actuators, NCM Type are supplied with bearings and a shaft. This type is generally smaller in diameter and longer in length. Higher forces can be achieved by increasing the number of poles, which increases the length, or by increasing the diameter. The main advantage is that there are no moving leads since the coil assembly is stationary. Optional no power magnetic latching is available at one or both ends of the stroke.

It should be noted that for both types of actuators, longer strokes are available but the efficiency or motor constant (Km) decreases as the stroke increases. This is due to the fact that the motor constant is inversely proportional to the stroke. If higher efficiency is desired for longer stroke actuators, the coil assembly can be wound as a multiphase coil and then it will have to be commutated.

• Small Size, High Force to Weight Ratio
• High Accelerations
• No Cogging or Commutation
• Custom Designs with Quick Turnaround Times
• High Flux Density Neodymium Magnets are Used
• Z Axis for Pick and Place Equipment
• Medical Diagnostic Probes and Laser Beam Steering
• Mirror Tilt and Focusing Actuators
• Miniature Position Control

Typical specifications for a non-commutated actuator are short stroke (0-3in or 0-75mm), accelerations of up to 20 times the acceleration due to gravity, continuous forces up to 100 lbs (0-100 lbs or 0-450N), peak forces up to 300 lbs (0-300 lbs or 0-1350N), and with the addition of a linear encoder or LVDT linear position resolutions down to 0.1 microns are acheivable.

Required Electronics:
Because of the very low inductance of the actuator, a DC linear servo amplifier is required to provide power to the Voice Coil. A programmable motion controller is required to close the position loop on the system.

Environmental Considerations:
The NC Actuators should not be mounted in an environment that is wet or excessively dirty or in an environment with ambient temperatures (>50ºC).

Mounting:
Mounting holes are provided on the housing, shaft and / or coil assemblies for mounting the actuator to customer supplied base and payload

Maintenance:
No maintenance is required.

(i.e. NCC05-15-020-2X is a moving coil actuator with 0.5" stroke, 1.5" OD, 2.0 lbs of continuous force, 2 pole magnet assembly and no special options)

Operating a voice coil motor using a function generator