Software for Simultaneous Control of Three Magnetic Bearings

Five-Axis, Three-Magnetic-Bearing Control Code (FATMaCC) is a C++-language computer program for controlling a magnetic thrust bearing in one degree of freedom and two magnetic radial bearings, each in two degrees of freedom. These bearings levitate a vertical-axis rotor for experiments on the effects of vibrations on turbo-machinery. When executed on a 1-GHz processor, FATMaCC can control the bearing/rotor motions in either a decentralized or a centralized (modal-control) manner at a loop time of 56 μs. Through keyboard entries, the user can modify such bearing parameters as stiffness, damping, and bias. A module in the program generates signals that can be superimposed on the radial-bearing x- and y-axis control signals to generate forces that excite rotor vibrations. There is an option to modulate the radial bearing control signals with cosine and sine functions, to make the radial excitation force vector rotate about the nominal central bearing axis. There is also an option to excite rotor rigid-body modes; depending on the polarities of the excitation signals applied to the radial bearings, either the bounce or the tilt mode is excited.