A novel double-action actuator based on ferrofluid and permanent magnets

In this article, an electromagnetic actuator with a movable non-magnetic disc immersed in a ferrofluid that is exposed to a non-uniform magnetic field generated by permanent magnets is presented. The position of the levitated disc is stably controlled by the current in a command coil. Numerical simulations and experimental tests show that the actuator has linear transfer characteristics force versus current and displacement versus current. The device can ensure the highest ratio of force/size and the best energy efficiency for the actuators using a non-magnetic body immersed in a ferrofluid. Examples of possible applications are precision positioning systems and semi-active vibration dampers.