| 摘要 |
A rotary electromagnetic actuator is provided which is suitable for opening and closing a valve for example. The actuator comprises a rotor (10), a stator (16), and a biasing arrangement (20, 100, 102, 104, 106) for applying a torque to the rotor during at least part of its rotation. A plurality of stable rest positions (200; 316, 318; 400) for the rotor are defined by forces acting on the rotor and the actuator is controllable to move the rotor from one stable rest position to another. The actuator displacement resulting from movement of the rotor from a primary rest position to a second rest position is greater than the displacement resulting from movement of the rotor from the primary rest position to a third rest position, with the rotation of the rotor from the primary rest position to the second rest position and from the primary rest position to the third rest position being substantially equal and in opposite directions. |
