Exploring cogging free magnetic gears

Abstract

The coupling of two rotating spherical magnets is investigated experimentally, with particular emphasis on those motions where the driven magnet follows the driving one with a uniform angular speed, which is a feature of the so called cogging free couplings. The experiment makes use of standard equipment and digital image processing. The theory for these couplings is based on fundamental dipole-dipole interactions with analytically accessible solutions. Technical applications of this kind of coupling are foreseeable particularly for small machines, an advantage which also comes handy for classroom demonstrations of this feature of the fundamental concept of dipoledipole coupling.

Dynamics of a magnetic gear with two cogging-free operation modes

“…shows the experimental setup, which is very similar to the one described by Borgers et al [10]. The two spherical neodymium permanent magnets have a diameter of 19 mm and are each attached to a shaft with their dipole moment aligned perpendicular to the rotation axis with a precision of about 3 • .…”

“…The results shown in this article stem from experiments with parallel rotation axes of input and output so that Θ ≈ Φ applies. [10], this article shows the dynamic behavior of the output when the input magnet is driven with a constant frequency. Thus, friction is an important additional parameter in our system which we determine experimentally by keeping the input angle fixed and analyzing the oscillation of the output around its equilibrium position.…”

“…Following refs. [7,10], the equilibrium position for the angle β 0 of the output as a function of a fixed input angle α 0 can be written as…”

“…We use THD F > 1 To further investigate the transition between these phases, δ is shown in Fig.6 for different driving frequencies of the input f at constant shaft angles Θ = Φ = 31 • . This way of presenting the data is adopted from the work of Borgers et al [10]. It is explained by a more detailed diagram in the top part of Fig.…”

“…The shaft angles near Θ = 0 • and Θ = 54.74 • -the cogging-free cases [7,10]-are characterized by a minimum of RMS δ = √ Var(δ). Once the shaft angles approach Θ = 35.26 • , we reach a maximum of this value.…”