Digital Control of Magnetic Bearings Supporting a Multimass Flexible Rotor

This paper considers the characteristics of magnetic bearings used to support a three mass flexible rotor operated at speeds up to 14,000 RPM. The magnetic components of the bearing are of a type reported in the literature previously, but the earlier analog controls have been replaced by digital ones. Analog-to-digital and digilal-ln-analog converters and digital control software were installed in a PC. This PC-based digital controller was used to operate one of the magnetic bearings on the test rig. Basic proportional-derivative control was applied to the bearings, and the bearing stiffness ami damping characteristics were evaluated. Particular attention is paid to the frequency dependent behavior of the stiffness and damping properties, and comparisons are made between the actual controllers and ideal proportional-derivative control. Presented at the 44th Annual Meeting in Atlanta, Georgia May 1–4, 1989