@ARTICLE{Kumar_Prabhat_Modelling,_2024,
 author={Kumar, Prabhat},
 volume={Early Access},
 journal={Archive of Mechanical Engineering},
 howpublished={online},
 year={2024},
 publisher={Polish Academy of Sciences, Committee on Machine Building},
 abstract={This paper investigates on developing a novel model-based identification technique for the simultaneous identification of severe faults such as the unbalance in the rotor and transverse crack in the shaft supported on foil bearings. With plenty of advantages over rolling element bearings or fluid film bearings, foil bearings have been used as the supported bearings in rotating machines such as fuel cell-electric air compressors, blowers, expanders, air cycle machines, etc. In the present article, a rotor model consisting of a cracked and unbalanced rotor with a disc in the middle supported by foil bearings has been considered for easier understanding of online identification of faults in high-speed rotating machines. Dynamic equations of motion of the rotor-foil bearing system have been derived based on the equivalent stiffness concept of shaft-foil bearing, inertia force, unbalance force, and crack force relying on the switching crack concept. The solutions of the equations, i.e., time domain displacement responses, orbit plots, etc. have been obtained numerically using the Simulink inbuilt Runge-Kutta method for different values of spin speed of the rotor and ramp-up speeds. The shaft centreline orbit is found to have eight shaped and asymmetric about the axes due to presence of crack and unbalance faults. The force due to unbalance fault gets dominated over the crack force at the higher speeds. Moreover, the orbit line is also observed to be thicker at higher level of noise addition in the responses. As the switching crack force contains multiple harmonics, a full spectrum analysis has been done to investigate both the forward and backward rotor whirls. The frequency-based rotor displacement is utilized to illustrate an identification algorithm for the estimation of the dynamic coefficients of foil bearings, additive crack stiffness, and magnitude as well as phase of disc unbalance. The identification algorithm is found to be quite suitable for the estimation of system and faults parameters even with addition of different levels of noise signal and modelling errors.},
 type={Early access},
 title={Modelling, analysis, and identification in a cracked and unbalanced Jeffcott rotor supported on foil bearings},
 URL={http://journals.pan.pl/Content/131946/PDF/AME_150566.pdf},
 doi={10.24425/ame.2024.150566},
 keywords={foil bearing, crack, unbalance, identification, full spectrum},
}