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

Abstract

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.

Study of the magnetic force delivered by an actuator with nonlinear ferrofluid and permanent magnets

“…The principle of a bidirectional actuator that uses a nonmagnetic body immersed in a ferrofluid differentially magnetized by two magnets is illustrated in Fig. 1 [15,16]. Because of the firstorder bouncy magnetic force in the ferrofluid, the cylindrical nonmagnetic body is levitated in the central position for zero current in the coil.…”

“…This is possible if we ensure two magnetic fields in the ferrofluid acting in opposite directions, produced by coils or permanent magnets. The differential change of the magnetic fields can be obtained in two ways [15,16]: (i) with differential currents in the two coils (I 1 = I 0 + I ,…”

Study of the influence of ferromagnetic material on the characteristics of an actuator based on ferrofluid and permanent magnets

“…2 is used for numerical simulations concerning the effect of introducing ferromagnetic material in the ferrofluid actuator structure, with or without premagnetizing magnets. In order to obtain a linear transfer characteristic and a double action effect two solutions can be used: either a) an initial active ferrofluid magnetization by means of a current I 0 and a differential command current ( 0 ǻ I I ± ) as we demonstrated before in [9], (Fig. 3) The results of the COMSOL simulations are presented in Fig.…”

“…Such a large scale prototype with optimized magnetic field, using a coil with a ferromagnetic core, a field former (ferromagnetic cylinder) and a ferrofluid with cobalt particles, was able to position loads of up to one kilogram, on small distances of 2-3 mm. An innovating idea applied for the actuator described in [9] consists in the use of two opposed permanent magnets to create a powerful magnetic field gradient in a ferofluid that contains a non-magnetic disc, whose motion is rigorously and stably controlled by the current in the coil. In this way larger drive forces can be generated for the same actuator size, than in the case of ferofluid actuators presented in literature and described above.…”

Ferrofluid-Based Shape-Controllable and Fast-Responsive Micro-Pumping and Valving Actuation

“…However, recent advances in nanotechnologies and nanomaterials have opened up new design opportunities that are based on very different actuation mechanisms. Since its discovery by National Aeronautics and Space Administration (NASA) in 1963 [1], ferrofluid has been used to form micro-channels in a range of applications, such as in heat transfer [2]- [5], chip cooling system [6]- [9] and drug delivering [10]- [14], with varying degrees of success. Although ferrofluid has been used for micro-pumping by Evrim and Arzu [15], [16],they use a mechanical means to generate rotating magnetic flux to actuate the ferrofluid valves.…”