Study of a ferrofluid actuator with levitating nonmagnetic disc

The paper presents a ferrofluid actuator with a nonmagnetic disc, whose position can be controlled by a command current in the surrounding coils. An exact analytical expression for the force acting on the nonmagnetic disc is determined for a simplified model, and a numerical analysis based on FEM is also performed for the real device model. The COMSOL Multiphysics results concerning the magnetic force, obtained using three alternative methods, are used in determining the levitation position of the mobile component. Two methods of feeding the coils are studied: equal currents in opposite directions and currents with a differential variation, the second one proving to render a linear or quasi-linear characteristic force versus command current variation.