MULTI-BEARING ROTOR MODEL UPDATING USING EXPERIMENTAL MODAL AND RESPONSE DATA

摘要

Recent investigations to improve the monitoring of rotating machines tend to use mathematical models of rotors supported by hydrodynamic bearings, which are able to correctly represent the dynamic behaviour of rotating shafts under defined working conditions. The possibility of updating finite element model parameters from experimental data, commonly used for undamped on gyroscopic structures, is thus studied for multi-bearing rotor systems. The strategy adopted can be described in two successive stages: first, the non rotating shaft model, corresponding to free boundary conditions, is updated thanks to classical methods; second, linearised bearing Characteristics are determined. For this latter purpose, we adapt here methods, the basic idea of which was developed in previous papers; they are based on either modal data or measured responses relative to an unbalance excitation, located only at bearing locations. This new approach has been tested on a semi-industrial device, which is a 4 meter long rotating shaft composed of two linked rotors, supported by 4 bearings. Initial stiffness and damping linearised bearing characteristics introduced are obtained as solutions of the Reynolds' equations. Even though the availibility of experimental data was very limited, application of the comprehensive method has permitted to improve the agreement between part of measured and calculated data.