GB1485290A - Magnetic bearing apparatus - Google Patents

Abstract

1485290 Automatic control of magnetic bearings SPERRY RAND CORP 19 Dec 1974 [14 Jan 1974 (2)] 54833/74 Heading G3R [Also in Division F2] A magnetic bearing, rotational for a gyroscope or providing vehicle suspension, for a member movable relative to another in two orthogonal directions comprises magnetically permeable cores on each member having polepieces which together define four gaps, one of the cores having a permanent magnet whose flux resists movement in one direction, resulting instability in the other direction being overcome by the provision of at least two electromagnetic coils on the said core, energized in response to movement in said other direction, and means are provided for modifying the electromagnetic flux in a way which augments the resistance to movement in the said one direction. Fig.2 shows part of a magnetic bearing for a gyroscope shaft 12. The shaft carries a generally W-shaped, in cross-section, core 35 while a stationary support has cores 50, 51 with a permanent magnet 31 and coils 32, 33 together defining gaps G1 ... G4. The permanent magnets resist radial movement since the pole faces tend to align in the position of minimum reluctance, and the inherent axial instability of this arrangement is prevented by energizing the coils to produced fluxes of one polarity in G1, G2 and the opposite in G3, G4 in response to an axial position sensor not shown in Fig. 2. The energization of one coil is varied by the amplified displacement error signal and the other by its time derivative, circuit Fig. 4 (not shown). The construction of an actual bearing is described, Fig. 3 (not shown); it includes copper damping rings in the pole faces and roller bearings for "back-up" support for violent movements. During run-up or slow down the electromagnetic flux is modified by an additional, constant, current, in the same direction in each coil; it is shown that this increases radial stiffness, and so may avoid transient resonances. The reversal may be effected by a tachometer signal, for a prescribed time, or by a resonance, radial, detector. A six-gap construction is envisaged, Fig. 6 (not shown). To support a vehicle, Fig. 7 (not shown), the W cores are placed on edge to form rails while the other cores carrying the coils and the permanent magnet are carried by the vehicle, which also has the energizing and control apparatus. The detectors sense the gap between the cores.