Estimation of nonlinear damping in rotor bearing systems using continuous wavelet transform based approach is proposed. Krylov-Bogobliubov method is used to obtain the approximate analytical solution for the nonlinear equation of motion of the rotor-bearing system. The envelope of the free vibration signal is extracted using the wavelet based approach to identify the nonlinearities in damping. Two different nonlinear damping models are studied using the proposed approach. Two examples are illustrated as coupled and uncoupled versions of equation of motion of a rotor-bearing system including nonlinear viscous external and internal damping. The performance of the method is tested on signals acquired from experiments and found successful. © 2016 Elsevier Ltd.

A. Seshadri Sekhar

Department of Mechanical Engineering

N. Harish Chandra

BEARING PADS

Control nonlinearities

Damping

Equations of motion

FAILURE ANALYSIS

Fault detection

Mathematical transformations

Nonlinear equations

Wavelet analysis

approximate analytical solutions

Continuous wavelet transform

Equation of motion

HILBERT HUANG TRANSFORMS

Internal Damping

Nonlinear damping

ROTOR-BEARING SYSTEM

WAVELET-BASED APPROACH

Wavelet transforms

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IIT Madras

Mechanism and Machine Theory

In a rotor-bearing system running with uniform angular acceleration, after running through the resonance, typical beat vibrations occur because the response of the system consists of the natural and excited motion. Shortly after resonance both are vibrations with frequencies close to each other. The present study explains a method for estimating damping of rotor-bearing systems from transient beat characteristics observed during the run-up stage. A mathematical justification is provided that the transient response of the rotor-bearing system consists of a beat response when the system crosses resonance. It is also clear from the mathematical model that the beat phenomenon observed depends on the level of damping in the system. The beat time period is also dependent on the angular acceleration of the system. This beat response is considered for wavelet analysis and the damping is estimated. Angular acceleration (α) of the rotor often increases the damping effects. This paper investigates how the damping ratio changes with respect to different angular acceleration values of the rotor-bearing system. Experimental validation of the beat phenomenon and damping identification is done for a rotor-bearing system. Validation for the above proposed method is done by the half-power bandwidth method of the run-up response and logarithmic decrement method of the beat response. A damping estimation from the impulse response of the stationary rotor by using wavelet transforms is also presented and validated using the logarithmic decrement method. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

JVC/Journal of Vibration and Control

Estimation of damping in rotors using complex morlet wavelet transform

Many types of rotating components commonly operate above the first or second critical speed and they are subjected to run-ups and shutdowns frequently. The present study focuses on developing FRF of rotor bearing systems for damping estimation from swept-sine excitation. The principle of active vibration control states that with increase in angular acceleration, the amplitude of vibration due to unbalance will reduce and the FRF envelope will shift towards the right (or higher frequency). The frequency response function (FRF) estimated by tracking filters or Co-Quad analyzers was proved to induce an error into the FRF estimate. Using Fast Fourier Transform (FFT) algorithm and stationary wavelet transform (SWT) decomposition FRF distortion can be reduced. To obtain a theoretical clarity, the shifting of FRF envelope phenomenon is incorporated into conventional FRF expressions and validation is performed with the FRF estimated using the Fourier Transform approach. The half-power bandwidth method is employed to extract damping ratios from the FRF estimates. While deriving half-power points for both types of responses (acceleration and displacement), damping ratio (ζ) is estimated with different approximations like classical definition (neglecting damping ratio of order higher than 2), third order (neglecting damping ratios with order higher than 4) and exact (no assumptions on damping ratio). The use of stationary wavelet transform to denoise the noise corrupted FRF data is explained. Finally, experiments are performed on a test rotor excited with different sweep rates to estimate the damping ratio. © 2013 Elsevier Ltd.

Journal of Sound and Vibration

Swept sine testing of rotor-bearing system for damping estimation

Soil Dynamics and Earthquake Engineering

Estimation error of the half-power bandwidth method in identifying damping for multi-DOF systems

Journal	Data powered by TypesetMechanism and Machine Theory
Publisher	Data powered by TypesetElsevier Ltd
ISSN	0094114X
Open Access	No