• Topic
• Acknowledgements

Topic

The axial passive magnetic bearing comprises an inherent ironless permanent magnet power generator, a simple signal control unit and an electromagnetic actuator. The power generator comprises three coil systems - the first furnishes raw actuator power, the second senses axial position and the third supplies the signal control unit. The actuator was designed similar to a loudspeaker coil. It is located in the close vicinity of the power generator. Hence, the electrical energy does not need to be transported over long distances.

The bearing possesses load capacity and stiffness characteristics that can be similar to those of conventional active magnetic bearings but without the need of expensive and complicated sensors, power amplifiers and control systems. It can be conceived for almost arbitrary available power and stiffness requirements. As long as the rotor is in the axially centred position, very low losses are present. To achieve this goal, the present design does take advantage of some few active electronic elements.

Therefore, the project result is a newly designed and build demonstrator. Its actuator was designed to supply a steady force of about 10N and peak forces of about 30N. By means of a simple analogous proportional-differential regulator, an axial stiffness of about 1N/m·rpm was measured - giving 2kN/m to 25kN/m depending upon the rotation speed. The use of a more sophisticated regulator will allow better actuator control and hereby push stiffness above 100kN/m. In this case, of course, the actuator should be enforced to sink more power without overheating.

Acknowledgements

I would like to thank Prof. Bleuler, Roland Moser and Jan Sandtner for their generous assistance.

A particular thank goes to the mechanics team of the microtechnology section who prepared the custom parts and the ITV Sintermetalle GmbH that shipped the high speed glide bearings.

Lausanne, 15/3/2002

Marcel Leutenegger