Analytical determination and simulation of frequency response functions of a structure with a rotating component for the purpose of system identification for condition monitoring of machinery

This paper outlines the method of obtaining the frequency response functions of a rotor system with strong gyroscopic effect and simulating it using MATLAB. The rotating effect causes unsymmetry in the system matrices, resulting in complexity in decoupling the mathematical models of the system for the purpose of modal analysis. A different method is therefore required, which can handle general system matrices rather than symmetrical matrices, which is normal for passive structures. In this paper the mathematical model of an overhung rotor system with two degrees of freedom is expressed. This model is then used to extract the right and left eigenvalues/vectors and subsequently the frequency response functions are extracted and simulated. MATLAB is used to carry out such simulation, since it has good capability for eigen analysis and also good graphical facility. The reflection of splitting of critical speeds of a rotating rotor on the frequency response functions are shown.