Stabilization of one degree-of-freedom control type levitation table with permanent magnet repulsive forces
It is impossible to levitate an object by using only permanent magnets (PMs). Many researches have been reported to reduce the number of control degree-of-freedom (DOF) in magnetic levitation systems. This paper presents a one-DOF control type magnetic levitation table supported by repulsive forces of four sets of PMs. Each set of PMs is composed of two PMs on a fixed frame and one PM on the levitated table. The PMs are located at the four corners of the rectangular table and the corresponding positions of the frame. The magnetic poles of the PMs on the table are opposed to those of the fixed PMs, so that repulsive forces act on the table and the frame. This paper, first, discusses theoretically the relative position range of the sets of PMs to the center of gravity of the table from the viewpoint of the stability condition of the motion of equation. In the discussion, the repulsive force and stiffness produced by a set of the PMs are assumed to be known parameters because they can be numerically calculated. Then an experimental table is constructed, in which the unstable motion is actively stabilized by a linear motor. Dynamic responses are measured, and results prove that the proposed magnetic levitation table is successfully held in stable equilibrium by only one-DOF active control. (C) 2002 Elsevier Science Ltd. All rights reserved.
stability permanent magnet repulsive force magnetic levitation linear motor