Characteristic Parameters Estimation of Active Magnetic Bearings for Varying Controlling Parameters

Online condition monitoring of rotor systems with the help of active magnetic bearings (AMBs) has been achieved more importance for the last few decades due to its ability to work in a feedback loop. Proportional-integral-derivative (PID) has three characteristic gain parameters, namely proportional (K_P), integral (K_I) and derivative (K_D). The main purpose of the controller is to provide current for the steady operation of the system. The stability condition of the system is achieved by applying Routh–Hurwitz stability criteria. The stable responses of the system are obtained by tuning the PID controller. Ziegler–Nichols tuning method is used to acquire the least settling time for different controlling parameters. Two different sets of PID controlling parameters are considered for tuning the system against different sets of frequency range. For identifying the characteristic parameters, two different sets of PIDs are selected for the frequency range of 35–51 Hz. A total of 10 operating speeds are selected randomly between the frequency ranges to generate the independent responses that are used in identification algorithm. In this article, a numerical experiment has been performed to identify characteristic parameters of the active magnetic bearing (AMB) along with dynamic parameters of coupling misalignment. An approach is proposed to evaluate the unknown parameters for two different sets of PIDs.