Applications that exploit diamagnetic properties for practical levitation require the integration of permanent magnets in a hybrid system. Strong permanent magnets provide the lift capacity to balance the forces of gravity. Diamagnetic material used with selectively positioned permanent magnets provides the stability to keep the levitation balanced within reasonable limits. SRI recently patented a hybrid levitation system based on permanent magnets for lift and on diamagnetism for the necessary control stability.

In SRI's system, many powerful neodymium-iron-boron bias magnets are mounted on a rigid support structure above a movable transport conveyance. The rigid support structure is stationary. Lift magnets are mounted to the movable transport conveyance (see Figure 1). The bias and lift magnets provide the attractive force necessary to counteract the force of gravity. Fixed magnet arrays are mounted to the same support structure as the bias magnets and straddle the diamagnetic bearing plates that are mounted to the transport conveyance. The diamagnetic bearing plates provide a fraction of the lift through their repulsive force relative to the fixed magnet array. The plates also provide sufficient repulsive force to counteract the attractive force of the bias and lift magnets. Stop rollers prevent accidental interference between the bearing plates and the fixed magnet array. The clearances between bearing plates and magnet array are small, on the order of 1 mm.

Providing that lift forces can be balanced correctly, how can lateral stability be achieved? We can do so by placing the lift magnet at a strategic location in the bias magnetic field. (We determine the location by computer modeling the magnetic field.) At this location, magnetic lines of force hold the lift magnets and transport conveyance in a neutral position under the bias magnets.

Eddy currents also are used to provide stability or opposition to motion in one direction. An aluminum plate mounted on the transport conveyance provides eddy current dampening and additional lateral support. When an electrically conductive material (in this case, aluminum) is moved in a magnetic field, an electric current is generated. (This is the basic principle of the electric generator. Copper conductors moving in a magnetic field generate an electric current that in turn generates its own magnetic field.) The dynamically introduced magnetic field repels the magnetic field of the fixed magnetic array and helps with lateral support. Eddy currents can also provide braking forces.