&lt;title&gt;Laser-based measurement system for measuring the vibration on rotating discs&lt;/title&gt;

Journal of Vibration and Acoustics

2013

This paper describes a computationally simple method to isolate transient vibration from rotating components whose frequency is tightly linked to rotation and to modes of vibration. The results can be viewed as an enhancement of computed order tracking or amplitude demodulation of multiple crossing frequency terms. By measuring the response with an array of sensors, one can compute the relative, instantaneous phase between different sensors and thus obtain information about the spatial behavior of different components with different wavelengths, frequencies, and traveling directions. An array of sensors would thus exploit spatial information to separate different vibration modes and thus gain deeper insight into the dynamical behavior. The proposed method is suitable for whirling shafts and rotating disk-like structures. It is computationally simple and fast while providing better separation of components than single sensor based approaches, in particular when ordinary methods fail to separate close frequencies. It is demonstrated that through the exploitation of cyclic symmetry of rotating structures and the angular periodicity of the vibration modes, the spectral contents of different modes can be separated. Simulated and measured data demonstrate the merits of the proposed algorithm.

“…Refs. [25][26][27]) or larger number of sensors to decompose the vibrations, as has been shown before [19,22]. The present problem is similar to what was presented in Ref.…”

Section: Introductionsupporting

confidence: 67%

Directional Order Tracking in Rotating Machines

Journal of Vibration and Acoustics

2013

“…These systems need to be described using Floquet's theory (Genta 1988;Yakubovich & Starzhinskii 1975), where the response to a pure sinusoidal excitation F 0 cos ωt gives rise to a large number of frequencies in the response spectrum, i.e. nΩ ± pω, n, p integers (Bucher et al . 1994).…”

Section: (Iii) General Anisotropic Bearingsmentioning

confidence: 99%

Modal analysis and testing of rotating structures

Philosophical Transactions of the Royal Society of London. Seri

Ewins

2001

Self Cite

This paper surveys the state of the art of modal testing or experimental modal analysis of rotating structures. When applied to ordinary, non-rotating structures, modal testing is considered to be well established. Rotating structures, on the other hand, impose special difficulties when one seeks to obtain the parameters of the dynamical model experimentally. This paper focuses on the necessary experimental techniques and their relationship to the current state of the existing theory. Existing modal analysis methods, models and techniques, and their advantages, limitations and relevance are outlined and compared. In addition, some new developments allowing us to circumvent some of the above-mentioned difficulties are presented.Rotating machines appear in almost every aspect of our modern life: cars, aeroplanes, vacuum cleaners and steam-turbines all have many rotating structures whose dynamics need to be modelled, analysed and improved. The reliability, stability and the response levels of these machines, predicted by analytical models, are generally not satisfactory until validated by experimentally obtained data. For this purpose, modal testing has to be employed and further advance is essential in order to overcome the difficulties in this area.In this paper, the differences between the mathematical models used for dynamic analysis of non-rotating and rotating structures are clarified. The implications of the model structure, in the latter case, on the application of modal testing are presented, as this is a point of great importance when experimental modal analysis is employed for rotating structures. Models with different degrees of complexity are being used for different types of rotating machines. A classification of such models is outlined in this work and the underlying assumptions and features are described in terms of a hierarchical complexity. Several applications of modal testing are reported here and some experimental evidence to support the validity of the theory is presented. Desired future activities, which are required to advance the theory and practice of this field, are summarized in conclusion.

“…where a are some coefficients A(x,) akt(x,y) (2) 410 Given a continuous scanning trajectory, which describes the position of the measuring laser-beam in the x-v plane as a parametric function of time, i.e.…”

Section: Hack6rolndmentioning

confidence: 99%

<title>Measuring vibration spatial information using continuous laser scanning</title>

1998

SPIE Proceedings

This paper presents a method, which allows one to use a single point laser vibrometer as a continuous sensor measuring along a line or a 2D surface. The mathematical background of the curve-fitting procedure and the necessary signal processing allowing one to extract the amplitude of sinusoidal vibration are discussed. In the current work, use has been made with an ordinary laser interferometer equipped with glavanometer-based x,y mirros. This system is not designed for continuous scanning therefore some effort needs to be spent in order to overcome the dynamical characteristics of this system. The potential of such an instrument, as demonstrated in this work, may encourage the development ofmechanically better scanning devices.