Linear Actuators

 

 

 

Providing constant force and fast positioning on a limited linear stroke (proportional actuators) or 2 stable position without current on both end stop (bi-stable actuators)

 

 

 

 

 

 

 

MMT linear actuators have been designed to provide an efficient, contactless, direct drive linear motion on a limited stroke . They are the result of several years of engineering at MMT and can achieve the hardest automotive requirements. A large variety of designs is now available, based on the use of ring, flat or even tile shaped permanent magnets.

The main features of this family of actuators are:

 

·               A constant force which is independent of the linear position for proportional actuators, or two stable position on both en stop position without current for bi-stable actuators.

·               A linear force versus current characteristic

·               Bi-directionality

·               High torque/ÖWatt/kg ratio

·               A contactless actuation principle

MMT 2-pole ring magnet linear actuator

MMT's bi-stable actuator

 

Additional functions, such as a magnetic return spring or analog contactless position sensing can also be implemented on both designs.

 

 

Thanks to the linearity of the torque versus current characteristic and to its independence of position on the proportional linear actuators, it is possible to operate our actuators in an open-loop against a spring or in a simple closed-loop mode by using a position sensor.

On the bi-stable actuators, some mechanical springs can also be added in order to linearize the force in function of the position. For the short stroke, the specifications of the proportional linear actuators are realized in smaller dimensions.

 

 

 

 

 

 

Basic Principle

 

Force versus position graph

The basic working principle of the proportional linear actuator is explained here above : a thin 2-pole permanent magnet is glued on a magnetic yoke. The stator is a 3-pole ferromagnetic part and the central pole is surrounded by a coil. When the coil is energized, the polarity of the central pole is opposite to that of the other poles, which results in a net force on the magnet.

That force is independent on the magnet’s position and proportional to the current input.

Long strokes can be achieved with available forces up to 500 N.

 

Force versus position graph

For the bi-stable actuator, the coil and the magnet are fixed on the stator. Without current, on an end stop position, the flux due to the magnet is mainly closed in the corresponding air-gap, and the position is stable. When applying a current in the coil, the flux due to the current is added or subtract to the flux due to magnet, and the yoke moves to close the preferred air-gap.

Shorter strokes can be achieved with available forces around few 100 N.

 

Main applications

 

 

 

 

 

 

MMT linear actuators are particularly well suited for applications requiring high force, small size actuation devices that can withstand millions of cycles in a demanding environment (dust, vibrations, etc…).

The contactless principle is particularly efficient for vibrating devices: the rotor may then be fixed on flexible blades to get a low cost and low friction system.

Our linear actuators are mainly used in the following applications:

Bike gears derailleur : the motion is created by 2 bistable linear actuators

Vibrating linear proportional  actuator or shaver

·               Reactive computer peripherals

·               Various pneumatic and hydraulic servo-valves (closed-loop mode or against a spring)

·               Scanning applications

·               Textile machines

·               Cutters for shavers and knives

·               Vibrators for pagers

·               Pick and place machines

·               Electromechanical switch.

Electromechanical switch

 

 

Patents for these technologies are granted or pending in USA, Europe, Korea and Japan

 

 

 

 

 
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