Fast-acting long-stroke bistable solenoids with moving permanent magnets

The force produced by conventional solenoids is an attraction force exerted across the air gap. It is, therefore, weakest at the beginning of motion when the gap is fully open. For that reason, such solenoids cannot be considered for fast-acting applications when the stroke is large. A new category of actuators is described, capable of providing high initial accelerations and, therefore, fast motion, even when the air gap is large. The concept consists in using the repulsion force that a stationary energized coil can exert on a moving permanent magnet. An experimental assessment of the performance capabilities of this type of actuator is presented. A mathematical model of their dynamics, suitable for design and optimization purposes, is also presented