Development of a Compact Magnetic Bearing Controller

This paper is about the development of a magnetic bearing controller, which is on a single printed circuit board of 80x125 mm2, and includes all the electronics for a five-axis magnetic bearing with five pairs of dc-biased electromagnets and five channels of displacement sensing. We explain our techniques, describe the controller, and show verification/test. We use voltage bias and voltage control, and our first technique is for building a thermally stable voltage bias with no extra electronics. The second is about power electronics. We let the four electromagnets of a radial bearing be wired as a square, and let each corner of the square be connected to a half bridge, so that four half bridges are enough for a radial bearing. The third is about sensor electronics. We let an eddy-current or inductive sensor probe be driven by a square wave voltage. Then, the current drawn from a dc power supply by the driving circuit is a baseband displacement signal. This gives a way for sensor electronics design, and what is designed turns out to be simple and capable of good performances.