Multivariable hybrid models for rotor-bearing systems

In this paper the flexural vibration of rotors, mounted on fluid film bearings, is considered. The rotor is described by a series of distributed and lumped elements. Frequency-dependent, transfer matrix methods are used to determine the characteristic determinant of the system. Direct search optimization techniques are employed enabling the whirl frequency and system stability to be determined and compared with results obtained from lumped modelling. Thereafter the dynamic stiffness matrix for the system is defined, from which the multivariable frequency response matrix for system can be established. Frequency domain identification techniques are employed enabling the multi-input, multi-output transfer function matrix of the system, to be determined. It is shown that by this method an accurate low order model can be achieved, for feedback control analysis and design. (C) 2000 Academic Press.