Magnetic actuators & motors technologies
Magnetic Actuators are using magnetic effects to generate forces which impacts on the motion of a part in the actuator.
A first large family of magnetic actuators is based on the magnetic forces acting at distance, the Laplace-Lorentz forces and the reluctance forces. Linear types offer strokes in the range of 1 to 20mm, and are complementary to piezo actuators. They can be sorted in 3 classes :
- Moving coil actuator : Placed in static magnetic field, a mobile coil driven by a current is submitted to the Laplace-Lorentz force. This force is proportional to the applied current. Thus these actuators are controllable. As first applications were loud-speakers, they are also called voice-coils. Cedrat has designed Voice Coils and LAT Limited Angle Torque actuators for various automotive, industrial or space applications.
- Moving magnet actuator : Placed between two magnet poles, a mobile permanent magnet can be switched from one pole to the other using coils. Such moving magnet actuators are bi-stable. They present high forces but are not so controllable. Miniature devices have been developed by Cedrat for locking and haptic applications.
- Moving iron actuator : A soft magnetic part placed into a coil system will naturally move in a way to minimise the system magnetic energy. In standard electro-magnets, this reluctance force is larger than Laplace force but is only attractive and not controllable. The new MICA Moving Iron Controllable magnetic Actuator developed by Cedrat thanks to Oseo is an innovative biased (polarised) electromagnet actuator where the force can be reversed all along the stroke. It is used for vibrations generation or for active damping in embedded applications. It offers larger stroke than piezo actuators. It offers higher forces and much less heating than any Moving coil actuator.
A second family of magnetic actuators is based on magnetically-controlled active materials. Two types are used at Cedrat for innovative devices :
- Magnetostrictive actuator : These actuators use the magnetostrictive effect, which consists in the deformation of a magnetostrictive material when subjected to a magnetic effect. For example magnetostrictive deformation of Terfenol-D achieves 1600ppm, making of this active material an interesting competitor of piezoelectric PZT ceramics for high power transducers or low voltage actuators.
- Magneto Rheological Fluid Actuator : A Magneto Rheological Fluid (MRF) can solidify when subjected to a magnetic field. This effect can be used for making various MRF-based actuators : valves, brakes, clutches, semi-active dampers, smart hydrostatic / hydrodynamic bearings…
A third broad family of magnetic actuators is the electric motors also called electric rotating machines. Cedrat computes all sizes as services but develops only small electric motors, as Brushless DC motors (BLDC) and stepper motors.
These technologies are presented in the examples presented hereafter. Also available for linear magnetic actuators is the Catalogue of New Magnetic Actuators. At last publications are available on magnetic actuators and electric motors.
| Single Phase Stepper Mini-Motor: SPSM-1 |
|
|
| Description: | A single phase rotating stepper micro motor featuring axial tunable air gap and flat permanent magnet has been developed in FP6 M2EMS EC project, in collaboration with CEA and ETA. This stepping motor is compatible with Si technologies. |
|
| Applications: | Micro-Motors, Micro-technologies... | |
| Status: | Proof of concept | |
| Magnetostrictive Actuators |
|
|
| Description: | CEDRAT Magnetostrictive actuators are solid state magnetic actuators based on Terfenol-D Giant Magnetostrictive Materials. They can be designed to produce high forces (>20kN) & large strokes (>200µm) at low voltage (<12V) in static or dynamic. |
|
| Applications: | High Force Generator, Low Voltage actuators, Sound transducers (sonar) ... | |
| Status: | Prototype | |
