On Self-Sensing Magnetic Levitated Systems

As a test-case for magnetic bearings and propulsion a 1 degree of freedom self-sensing magnetically levitated steel ball is under study. In this paper an overview of the design of a levitation system is given. It will appear that the easiest implementation of self-sensing magnetic levitation is to use a current controlled coil, and add a high frequency current to the actuating current for measuring the inductance of the coil. Therefor the voltage over the coil is demodulated using synchronous AM demodulation. An accuracy analysis is made for 1 DOF self-sensing magnetic levitation systems. Finally, upper bounds for the accuracy of such a system are given. It will appear that self-sensing magnetic leviation cannot be used in the system it was proposed for, therefore no experimental results will be given in this paper.