Online Condition Monitoring of a Flexible Rotor System with the Help of Active Magnetic Bearings

Health monitoring of rotating machines is highly important for continuously running plants such as power generation industries, cryogenic engines of space vehicles, and multi shaft aero engines. In past, vibration based condition monitoring techniques attained a prime position among the researchers but the vibration based condition monitoring technique has less adaptability in a higher frequency range; to overcome this limitation, online condition monitoring, i.e., active controlling with the help of controlling parameters of Active Magnetic Bearings (AMBs) is presented in this article. An identification methodology is developed to estimate the characteristic parameters of AMBs, coupling misalignment in addition with inherent unbalance of the system. Shafts are considered as flexible and modeled with the Euler–Bernoulli beam theory. Proportional–Integral–Derivative (PID) controller is used for controlling the current in AMB. Finite Element Method (FEM) is used to obtain Equations of Motion (EOMs) of the coupled rotor system. The developed EOMs are modeled in the SIMULINK^TM and solved by fourth-order Runga–Kutta method to obtain the displacement and the current response. Fast Fourier Transform (FFT) is used to convert the time domain responses into frequency domain responses. For brevity, half spectrum analysis is carried out to obtain the multi-frequency responses at different operating conditions. The proposed methodology is tested against different levels of measurement noise to check the robustness of the system for estimating the characteristic parameters using multi-frequency responses.