Abstract
In practice, it is usually difficult to obtain the physical model of nonlinear, rotor-bearing systems due to uncertain nonlinearities. In order to solve this issue to conduct the analysis and design of nonlinear, rotor-bearing systems, in this study, a data driven NARX (Nonlinear Auto-Regressive with exogenous inputs) model is identified. Due to the lack of the random input signal which is required in the identification of a system′s NARX model, for nonlinear, rotor-bearing systems, a new multi-harmonic input based model identification approach is introduced. Moreover, the identification results of NARX models on the nonlinear, rotor-bearing systems are validated under different conditions (such as: low speed, critical speed, and over critical speed), illustrating the applicability of the proposed approach. Finally, an experimental test is conducted to identify the NARX model of the nonlinear rotor test rig, showing that the NARX model can be used to reproduce the characteristics of the underlying system accurately, which provides a reliable model for dynamic analysis, control, and fault diagnosis of the nonlinear, rotor-bearing system.
Highlights
The rotor-bearing system is the main component of large-scale, rotatable equipment such as, e.g., aircraft engines and gas turbines, etc., and most of the rotor-bearing systems are significantly affected by nonlinearities [1]
NARX approach is used in the system identification of the rotor-bearing system which is shown in Figure 1, where the system is subjected to unbalanced force meω 2 sin(ωt) in the horizontal direction
Mathematical models are important in the analysis, design, and fault diagnose of rotor-bearing
Summary
The rotor-bearing system is the main component of large-scale, rotatable equipment such as, e.g., aircraft engines and gas turbines, etc., and most of the rotor-bearing systems are significantly affected by nonlinearities [1]. Zhou and Chen [7] introduced a dual rotor-ball and bearing-stator coupling dynamic system Those physical models are relatively simple to describe complex, nonlinear, rotor-bearing systems such as, e.g., large centrifugal compressors and steam turbines, etc., where strong nonlinearities have to be taken into account [8]. To address the aforementioned issue, in this study, a multi-harmonic signal generated by a speed-up process is applied as the system input to establish the NARX model. The approach of identifying the NARX model of the nonlinear, rotor-bearing system is proposed by using the speed-up harmonic signal.
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