Identification of speed-dependent parameters in rotor systems supported on tilting pad journal bearings and active magnetic bearings in the presence of combined misalignment

The present work deals with the identification of speed-dependent misalignment parameters in a multi-disk coupled rotor system supported on Tilting pad journal bearings (TPJB) and Active magnetic bearings (AMB). The stiffness matrix of misaligned coupling is modelled as the sum of static coupling stiffness (SCS) and additive coupling stiffness (ACS) matrices. The presence of parallel and/or angular misalignments gives rise to ACS matrix and its coefficients represent misalignment in/about a given direction. ACS coefficients are time dependent and a suitable mathematical function has been chosen to define the time varying nature of these coefficients. The global equations of motion (EOMs) are assembled and solved in time domain to obtain rotor vibration and AMB current data. This data is processed by full spectrum Fast Fourier Transform, and subsequently input to the identification algorithm. The stiffness and damping of TPJBs, stiffness of AMBs and ACS coefficients that correspond to misalignment are estimated at six different speeds along with speed-invariant disc unbalances, and SCS coefficients. The robustness of algorithm is tested against measurement noise and modelling bias. ACS coefficients have been identified within reasonable error margins. Finally, the method of application of the algorithm to real rotors is presented. The novelty of the work is the development of an inverse problem for the identification of parallel and angular misalignments in real rotors.