An electronically-operated, normal-force, variable-reluctance actuator

Most linear, variable-reluctance, electromagnetic actuators utilise the `tangential´ or `aligning´ component of reluctance force. All of these devices are also exposed to a `normal-force´ of magnetic attraction which acts directly across the air-gap and does not contribute to the actuator output and is typically an order of magnitude greater than the mean tangential force. This unstable force has been exploited for decades, in an uncontrolled manner, over short stroke motions, e.g. in simple relays, but the authors decided to re-examine its potential in the light of modern electronics. The actuator harnesses this large force using a simple ratcheting design to integrate successive short strokes produced by the electromagnet. The novelty of this drive lies in the fact that it achieves blocking and ability to drive in either direction with only two operating coils