Magnetic actuator with ferrofluid and non-magnetic disc

Abstract

The paper studies an actuator based on magnetofluidic forces acting on a non-magnetic disc plunged into a ferrofluid that is exposed to a non-uniform magnetic field generated by magnetic inductor(s). The input output equations (force -current and displacement -current) that describe the behaviour of two types of actuators are established. The expression of the force generated on the nonmagnetic disc is determined analytically for the particular conditions imposed by the two actuator configurations: a) simple, with one magnetic inductor; b) differential, with two inductors. The derived relations enable a comparative study of the two types of actuators. The results show the superior performance of the differential actuator. The latter was tested as a current to displacement transducer in an electropneumatic converter.

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

“…As may be seen, the force calculated using (8) is larger than that measured experimentally because the value for H I (z ) used in calculations was that for r = 0, which is the largest for z = constant. It is to be noted that there is still satisfactory agreement between the theoretical results obtained with (8) In Fig.13, the curves F m (I ) for three ferrofluids with different magnetic susceptibilities are plotted. The slope of the curve increases with susceptibility, as expected from (4).…”

“…The magnetic force was calculated with (8) for an experimental actuator model that used a MF-UTR type ferrofluid with known M (H ) characteristic. For this purpose, the ferrofluid magnetization was accurately determined knowing the field distribution produced by the magnets.…”

“…Using the above-mentioned procedure for the determination of M M and H I , the magnetic force F m can be calculated using (8). The results are illustrated in Fig.…”

“…This effect can be used in the levitation of the nonmagnetic body-the effect being known as the first-order bouncy magnetic force-or for generating forces and displacements with actuators designed for this purpose. Since 2000, [7] actuators based on this principle have been proposed both for small [8][9][10] and large forces [11][12][13], and a prototype made was capable of positioning loads of up to 1 kg on small distances of 2-3 mm. Most of these applicators work only in the vertical position, and the control of levitation is precarious because the restoring force due to gravitation is not adequate for stable positioning.…”

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

“…The actuator can be with simple action (one magnetic inductor) or with double action (differential, with two inductors). A double action actuator was tested as a current to pressure transducer in an electro-pneumatic converter [3]. This principle can be used in controlling the vertical motion of a non-magnetic body.…”