Estimation of the Dynamic Parameters of the Bearings in a Flexible Rotor System Utilizing Electromagnetic Excitation by a Built-In Motor

Abstract

Estimation of the dynamic parameters of bearings is essential in order to be able to interpret the performance of rotating machinery. In this paper, we propose a method to estimate the dynamic parameters of the bearings in a flexible rotor system. By utilizing the electromagnetic excitation generated by a built-in PM motor and finite element (FE) modeling of the rotor, safe, low-cost, and real-time monitoring of the bearing dynamics can be achieved. The radial excitation force is generated by injecting an alternating d-axis current into the motor windings. The FE model of the rotor and the measured frequency responses at the motor and bearing locations are used to estimate the dynamic parameters of the bearings. To evaluate the feasibility of the proposed method, numerical simulation and experiments were carried out on a flexible rotor system combined with a bearingless motor (BELM) having both motor windings and suspension windings. The numerical simulation results show that the proposed algorithm can accurately estimate the dynamic parameters of the bearings. In the experiment, the estimates made when utilizing the excitation force generated by the motor windings are compared with the estimates made when utilizing the excitation force generated by the suspension windings. The results show that most of the stiffness and damping coefficients for the two experiments are in good agreement, within a maximum error of 8.92%. The errors for some coefficients are large because the base values of these coefficients are small in our test rig, so these coefficients are sensitive to deviations. The natural frequencies calculated from the dynamic parameters estimated from the two experiments are also in good agreement, within a maximum relative error of 3.04%. The proposed method is effective and feasible for turbomachines directly connected to motors, which is highly significant for field tests.

Identification of dynamic parameters of journal bearings in an asymmetric rotor-bearing system

“…Moreover, as the dynamic parameters are speed-dependent, the sensitivity of measurement error is higher when the speed range is small (Tiwari et al , 2002). In recent years, many new devices and algorithms have been used to identify bearing parameters, such as bearingless motor (Chen et al , 2021; Chen et al , 2022), smart magneto-rheological bearing (Mahboubeh et al , 2022), robust method (Ahmad et al , 2023) and dual augmented Kalman filter (Yang et al , 2024).…”

A method for the estimation of oil film parameters in an asymmetric rotor-bearing system

“…Dynamic excitation force generated by exciters, such as hydraulic exciters and electromagnetic exciters, has been used for rotor-bearing system dynamic characteristic tests for many years. Compare with hydraulic exciters (Childs and Joel, 2009), the advantage of the electromagnetic exciter (Chen et al , 2021; Chen et al , 2022; Li et al , 2017) is that it can apply noncontact force on the rotor, and the characteristic of the rotor system will not be affected because there is no connecting and attaching component between the exciter and rotor. However, installing the exciter requires additional space or an extended shaft.…”

Tacholess estimation of time-varying dynamic coefficients of journal bearing based on the square-root cubature Kalman filter

“…However, accurate measurements of dynamic coefficients are difficult due to complicated installation, operation, maintenance, and on-site environment [3]. Therefore, it is critical to design a reliable method to estimate the dynamic coefficients of journal bearings for further evaluation of the overall performance and operating conditions of the rotor system [4].…”