Showing papers in "Mechanical Systems and Signal Processing in 1993"

TL;DR: The application of the spectrogram to the calculation of the time-frequency distribution of a gear vibration signal is examined in this article, where it is shown that the Gaussian function is well suited to calculate the energy distribution, giving a representation free from ripple and easy to interpret.

TL;DR: In this paper, a system is described which uses image processing techniques to assist in the automatic interpretation of gear vibration signatures for early failure detection and fault diagnosis, where the vibration signature of individual gear in a gearbox is extracted by the time domain synchronous averaging technique from the total vibration signal measured on the gearbox casing.

TL;DR: In this article, the authors describe the theoretical and experimental aspects of these higher order quantities and for the first time show that higher order transfer functions up to third order can be obtained in practice using standard sinusoidal excitation testing procedures.

TL;DR: In this paper, a theory is developed to show how the necessary mass and stiffness modifications can be computed using modal test results only, even when only a partial set of eigensolutions is available from such tests.

TL;DR: In this article, a system identification approach for damage monitoring in vibration mechanics is presented, which uses accelerometer measurements from the system at work so that the excitation is not controlled, usually not observed and may involve turbulent phenomena.

TL;DR: In this article, the authors proposed a method of identifying joint structural parameters using subset frequency response function (FRF) measurements, which can be applied to real structures usually having rotational and inaccessible dofs.

TL;DR: In this paper, both continuous and discrete time transfer functions of nonlinear systems are analyzed and interpreted in the frequency domain by investigating the properties and graphical representation of these functions, and the contributions that typical terms from non-linear time domain models make to the transfer functions are illustrated to provide a better understanding of the frequency response behavior of complex nonlinear dynamic systems.

TL;DR: In this paper, an iterative receptance method for the analysis of non-linear multi-degree of freedom systems with nonlinear stiffness and damping forces is proposed. But the application of the method is limited.

TL;DR: In this paper, a time-frequency analysis of vibration signals picked up on the outside and inside of an engine cylinder enables the identification of the excitation and propagation mechanisms inside the engine.

TL;DR: In this paper, various excitation methods are proposed for the effective use of complex modal testing for rotating machinery, based on the input/output relationships for complex signals, for the direct or indirect assessment of frequency response and coherence functions between complex inputs and outputs.

TL;DR: In this paper, the authors developed a genetic algorithm in the context of the actuator number and placement problem, which is loosely based on Darwin's "Survival of the fittest" theories.

TL;DR: In this paper, the concept of selective sensitivity is developed for dynamical excitation of viscously damped elasto-mechanical systems, which reduces ill-conditioning in identification of large systems.

TL;DR: In this paper, the application of sliding mode control to stabilise an electromagnetic suspension system is presented, and the performance and stability robustness as well as the practicality of the sliding mode controller are demonstrated using a laboratory EMSA system.

TL;DR: In this paper, the concept of colocation is extended to distributed transducers, and combinations of distributed and discrete transducers are affixed to self-adjoint distributed plants, where sensors and actuators are colocated only when they have both physically coincident spatial apertures and their spatial derivative orders are equal.

TL;DR: In this article, an "imagined" stiffness is added to the structure and the FRF of this perturbed structure is obtained from the measured FRFs of the original structure by a simple structural modification technique.

TL;DR: In this paper, an active adaptive structure made of piezoelectric materials is proposed and evaluated using Hamilton's principle and the linear PDE theory, where the structural adaptivity is achieved by a voltage feedback (open or closed loops) utilising the converse PDE effect.

TL;DR: In this article, the problem of finite element model updating of structures consisting of substructures connected through mechanical joints whose stiffness and damping properties are unknown is treated. But the model is updated by estimating the mechanical joint parameters via the curve fit of measured frequency response functions using a non-linear least-squares method.

TL;DR: In this paper, the concept of selective sensitivity is applied in simulation to the identification of a complex truss, and it is shown that, of the 36 adjustment parameters in the model, the number of adjustment parameters which must be simultaneously estimated is never more than two.

TL;DR: In this article, the chaotic dynamic behavior of non-linear mechanical systems with backlash is investigated and the forcing parameter field for the existence of chaos and the influence of damping on the chaotic behaviour have been investigated.

TL;DR: In this article, a non-linear model of the hydro-units at the power plant in Ilha-Solteira (Brazil) is presented, which takes into account magnetic interactions, seals, journal bearings, as well as unbalanced, constant, harmonic and stochastic excitation forces.

TL;DR: In this article, an adaptive procedure for statistical estimation of the ARMA parameters with elimination of that bias is presented, and the performances and limitations of the above procedure are determined by means of a large sequence of numerical simulations.

TL;DR: A brief review of the parametric spectral estimation method is presented, as well as report on some preliminary work that compares the two methods when applied to low speed rolling element bearings.

TL;DR: New complementary spectral-based approaches for system identification and coherence estimation which anticipate this mixture of processes involving random processes having infinite as well as finite energy are proposed.

TL;DR: In this paper, a semi-active control of structural vibrations via variable damping elements is proposed, which is insensitive to the spillover problem encountered in fully-active systems, and an algorithm based on sliding mode theory is developed and analyzed.

TL;DR: In this article, a multi-sensor system has been implemented for cutting process monitoring in a lathe, where the data dispersion inherent to a noisy signal suggests strict quantifier selection over a wide initial set.

TL;DR: In this paper, a basic concept of stiffness and damping control for truss structures using axial member actuators with a latch mechanism is investigated, where the axial actuator can drastically change to a very low stiffness by releasing the installed latch mechanism, and this low stiffness is effectively used for structural control.

TL;DR: In this article, an active dynamic vibration absorber is designed using the theory of output regulation with internal stability, and the aim of the control system is to reduce the vibration of the controlled object equipped with the absorber to zero at a specified frequency and to a non-resonant level at other frequencies.

TL;DR: In this paper, the authors describe how the time required to perform a stepped sine test may be reduced by recursively estimating the FRF value at a given excitation frequency.

TL;DR: In this paper, a speckle based fiber optic vibration sensor using subcarrier intensity modulation of the laser light source has been investigated, which allows the normally low frequency vibrating modal components, such as those found in large structures, to be frequency upshifted thereby reducing the degradation effects caused by low frequency noise.

TL;DR: In this paper, it was shown that the second and higher order Volterra kernel transforms can be approximated within a limited frequency range by a quotient whose denominator is formed from the poles of the first order in the restricted frequency range, the maximum number of terms in the polynomial being limited by the number of poles.