Magnetic braking: Simple theory and experiment

Abstract

A simple theory of magnetic braking in a thin metal strip is proposed. The predictions of the model are compared to experiment and good agreement is obtained. The experimental tests were conducted by spinning a thin aluminum disk of large radius between the pole pieces of an electromagnet. A field range of 0 to 150 mT was used.

Analytical results for rotating and linear magnetic brakes

“…To understand magnetic braking we can start with a simple model made up of an infinite thin metal strip moving under the field of a rectangular magnetic pole [5]. The braking force is obtained from the Lorentz force on the eddy currents, assuming that the current density is uniform inside the region of the magnet 'footprint'.…”

“…Previous analytical works on this subject either completely ignore the space charges induced on the disk, due to the technique used in the solution [14,18,19,20] or due to the simplicity of the model [5], or calculate these space charges only partially. According to the convenience, only ρ F is calculated, ignoring the surface charge density σ F [17] or, conversely, only σ F is calculated ignoring the charge density ρ F [12,13,15,16].…”

Eddy Current Brakes for Haptic Interfaces: Design, Identification, and Control

“…As a result of the motion, eddy currents -Foucault currentsare induced to create a resistive force that is proportional to the relative velocity, according Lorentz' Force Law. Although the phenomenon is difficult to analyze for complex geometries [19]- [21], the underlying relationship between angular velocity and torque can be derived with the help of several simplifying assumptions. To familiarize readers with the underlying relationships, a simplified model from the literature is outlined.…”

On the nonlinear electromagnetic coupling between a coil and an oscillating magnet

“…Furthermore, the dissipative nature of induction has led to developments in such areas as magnetic brakes [9][10][11] and structural vibration suppression [12][13][14][15][16], effectively replacing friction as a means of energy dissipation. The friction reduction offered by these applications lends itself to decreased wear and damage in various physical components, thus prolonging their useful service life.…”