A magnetic suspension system with a large angular range

Abstract

In order to explore and develop technology required for the magnetic suspension of objects over large ranges of orientation, a small-scale laboratory system, the large-angle magnetic suspension test fixture (LAMSTF) has been constructed at NASA Langley Research Center. This apparatus falls into the category of large-gap, actively stabiiized magnetic levitation systems. The hardware comprises five conventional electromagnets in a circular arrangement, each driven from a separate bipolar power amplifier. Electromagnet currents are commanded by a digital control system, implemented on a microcomputer, which in turn derives the position and attitude of the suspended element from an infrared optical system. The suspended element is a cylindrical, axially magnetized, permanent magnet core, within an aluminum tube. The element is "levitated" by repulsive forces, with its axis horizontal, 0.1 m above the top plane of the electromagnet conductor. The element is stabilized in five degrees-of-freedom, with rotation about the cylinder axis not controlled. By mechanical rotation of the sensor assembly, the suspended element can be made to undergo a full 360" rotation about the vertical axis. The controller accommodates the changes in magnetic coupiing between the electromagnets and the suspended element by real-time adaptation of a decoupling matrix. This report presents a review of the background to the problem of magnetic suspension over large ranges of orientation. Next, the design and operation procedures adopted for LAMSTF, and the system hardware are described. Finally, some performance measurements are shown, together with illustration that the major design objective-the 360" rotation, has been accomplished.

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