bluuebunny/crossref_metadata_2025_split huggingface dataset:
A System Identification Technique Using Pseudo-Wavelets for General Linear Systems
Authors: Hou Zhikun , Hera Adriana 
Published: November 2020

Abstract
A concept of pseudo-wavelet is proposed based on shifting and scaling of conventional wavelets and a related pseudo-wavelet transform (PWT) is defined. The paper presents two special pseudo-wavelets defined based on the frequency response functions of the first- and the second-order linear dynamic systems, respectively. A PWT-based system identification technique is developed to estimate the system parameters, including the time constant associated with a single real pole of the system and the natural frequency and the damping ratio associated with a pair of conjugate complex poles of the system. The proposed approach is illustrated for representative linear dynamic systems of up to the third-order and good estimates are obtained in all studied cases. Noise effects on the accuracy are also investigated. The paper presents a preliminary study of the PWT-based system identification technique for general linear dynamic systems.
Nonlinear Parametric Identification of Oscillating Cables Using Wavelets
Authors: Romeo Francesco , Gattulli Vincenzo , Benedettini Francesco 
Published: November 2020

Abstract
In the present study a wavelet-based procedure is applied for the parametric identification of a nonlinear discrete cable model on the basis of experimental data obtained from free-vibration dynamic tests. The 3D cable dynamics is described by two partial integro-differential equations in the transversal planar and nonplanar displacement components. By expanding such variables in series of linear eigenfunctions, a discrete model is obtained by applying a classical Galerkin procedure. The resulting set of nonlinear ODEs contains quadratic and cubic coupling terms. The core of the identification technique is the discretization of such nonlinear differential equations by means of orthogonal Daubechies scaling functions. The Wavelet-Galerkin solution of the nonlinear equation involving the scaling function expansion of nonlinear terms leads to an algebraic problem that has to be inverted in order to solve for the vector of unknown parameters. A sdof model able to describe the in-plane unimodal oscillations is considered. Numerical and experimental identification tests are presented. Accurate estimates of the linear and quadratic parameters are achieved from the moderate oscillation amplitude response of an experimental discrete cable-mass model. The accuracy of the cubic parameter estimate is shown to depend on the level of both the oscillation amplitude and noise.
Computationally Efficient Time-Domain Modeling of Fluid Transmission Lines
Authors: Manhartsgruber Bernhard 
Published: November 2020

Abstract
The behavior of laminar, liquid pipe flow can be simulated with Zielke’s method using a convolution integral for computing the wall friction from past velocity changes and a method of characteristics. The major drawback of Zielke’s method is the large consumption of computation time and computer memory due to the increasing sequence of past velocity values. The Zielke-Suzuki method replaces the convolution integral by a system of linear difference equations saving both memory and computation time. This paper shows how to formulate the Zielke-Suzuki method as a standard, discrete time linear system. The application of order reduction methods to this standard form gives a reduced system with identical input output behavior. Thus, a further improvement of the Zielke-Suzuki method with respect to both computation time and memory consumption has been reached.
Failure Prognosis Using Nonlinear Short-Time Prediction and Multi-Time Scale Recursive Estimation
Authors: Chelidze David , Cusumano Joseph P. , Chatterjee Anindya 
Published: November 2020

Abstract
In this paper we describe a new, general purpose machinery diagnostic/prognostic algorithm for tracking and predicting evolving damage using only available “macroscopic” observable quantities. The damage is viewed as occurring in a hierarchical dynamical system consisting of a directly observable, “fast” subsystem coupled with a hidden, “slow” subsystem describing damage evolution. This method provides damage diagnostics and failure prognostics requiring only the measurements from the fast subsystem and a model of the slow subsystem. Damage tracking is accomplished by a two-time-scale modeling strategy based on phase space reconstruction using the measured fast-time data. Short-time predictive models are constructed using the reconstructed phase space of the reference (undamaged) fast subsystem. Later, fast-time data for the damaged system is collected and used to estimate the short-time reference model prediction error, or a tracking function. An average value of the tracking function over a given data record is used as a tracking metric, or measure of the current damage state. Recursive, nonlinear filtering is used to estimate the actual damage state based on the tracking metric input. Estimates of remaining useful life are obtained recursively using a linear Kalman filter. This method is applied to an experimental nonlinear oscillator containing a beam with a crack which propagates to complete failure. We demonstrate the ability to track the evolving damage state of the beam using only strain time series data. We also give accurate predictions of remaining useful life, in real time, beginning well in advance of the final complete fracture at the end of experiment.
Structure-Excitation Modal Decoupling by Modification of the Involved Acoustic Modes of the Sound Insulating Enclosure
Authors: Papadopoulos Christos I. , Georgiou Ioannis T. 
Published: November 2020

Abstract
Several noise sources such as machinery with rotating or reciprocating parts routinely produce high levels of noise in narrow frequency ranges lying in the neighbourhood of the rotating or reciprocating frequency and their harmonics. When enclosures are used to isolate such noise sources, peak response might be observed at these frequency ranges due both to increased excitation amplitude and resonating phenomena caused by the interaction of the excitation with the acoustic modes of the enclosure. Especially in the low frequency range and for low or intermediate wall absorption, the acoustic response of the enclosure is modal and these peak responses can be intense. This paper proposes a methodology to minimize the effect of narrow-frequency-band noise by redistribution of the acoustic modes of the insulating enclosure. This can be achieved by shifting the enclosure acoustic modes away from the excitation frequency so as to make superimposed resonating phenomena less intense. For that, several variable geometric modifications of the enclosure walls are introduced. The magnitude of those modifications that will lead to sparse mode distribution in the neighbourhood of the excitation frequency is estimated by means of a combined finite element-optimisation method. The above methodology is applied to an orthogonal enclosure and two different narrow-band loads in the neighbourhood of 90 and 120 Hz are studied. It is shown that, for each frequency load, a feasible set of geometric modifications can be found so as for the neighbouring modes to be shifted and, consecutively, for resonating effects to be made less intense. Furthermore it is shown that feasible solution to the problem of simultaneous control of noise having two or more intense excitation frequencies is also attainable.
Quasi-Periodic Motions of Articulated Pipes Conveying Flowing Fluid
Authors: Szabó Zsolt 
Published: November 2020

Abstract
In this paper two nice examples are investigated where a ‘chain’ of n = (1, 2) pieces of rigid pipes contains incompressible and frictionless flowing fluid. We give an overview about the linear and nonlinear analysis of the autonomous system, i.e. when the pipes contain steady flow. Assuming pulsatile flow, the system becomes time-periodic. The stability charts of the linearized system are generated applying a numerical method based on Chebyshev polynomials. Finally, we analyze the effect of the nonlinear part in some critical points of the obtained stability charts and the dynamic behaviour of the original nonlinear periodic system is simulated numerically. The results are shown in Poincaré maps and bifurcation diagrams.
Geared Rotordynamic Systems on Hydrodynamic Bearings
Authors: Theodossiades S. , Natsiavas S. 
Published: November 2020

Abstract
The present study investigates response and stability characteristics of gear-pair systems supported on oil journal bearings. The systems examined are driven by a motor providing a known torque, which is transferred to a load element through shafts and a gear-box. Here, the emphasis is placed on the gear-pair action, by assuming that the interconnecting shafts are rigid. This results in mechanical models with strongly nonlinear characteristics, whose long time dynamics are then effectively studied by applying appropriate numerical methodologies. In this way, useful information is obtained for the influence of the loading, the gear mesh and the journal parameters on the system dynamic behavior, including periodic, quasiperiodic and chaotic response. Efforts are also directed towards predicting the onset of oil whirl instability and investigating its effects on the gear-pair dynamics.
Grazing Bifurcations of Initially Quasi-Periodic System Attractors
Authors: Dankowicz Harry J. , Piiroinen Petri T. , Nordmark Arne B. 
Published: November 2020

Abstract
This paper discusses the dramatic changes in system dynamics that arise as parameter variations lead to the appearance of grazing intersections between periodic and quasi-periodic attractors and state-space discontinuities. In particular, a method based on the discontinuity-mapping approach is employed to predict the effects of near-grazing interactions with the discontinuity surface solely based on information about the discontinuity and the pre-grazing trajectory and requiring no knowledge of the impacting system. An example from the study of legged locomotion is used to illustrate the significance of such grazing bifurcations on the presence of sustained gait in simple anthropomorphic mechanisms. The predictive power of the discontinuity-mapping approach is illustrated on a low-dimensional model example.
Steady State Vibrations of a Piecewise Linear System
Authors: Jazar G. Nakhaie , Golnaraghi M. F. , Swanson D. A. 
Published: November 2020

Abstract
In this paper we examine the dynamics of a mechanical system with a piecewise linear damping and stiffness, which is characterized as a strongly nonlinear system. Searching for the exact steady state periodic response of piecewise linear systems for harmonic excitations, lead to a set of transcendental equations which should be solved numerically. The strong nonlinear characteristic of the system is the reason for failure of most traditional perturbation methods in providing an approximated frequency response. In this paper we show that the averaging method of Krylov-Bogoliobuv-Mitropolsky (or multiple time scale method) may be used to find the behavior of this type of system.
Optimization of linear vibration isolators and engine mounts has a straightforward solution: the stiffness should be as soft as possible. Static deflection and maximum allowable relative mount displacement (rattle space) determine the limit of mount softness. Dividing the travel space into two (or more) stages enables us to use an isolator with a different stiffness for each stage. This is a simple method to have a more advanced passive mount isolator. However, this also makes the system piecewise linear, which has a strongly nonlinear behavior if the ratio of the two stages are far from unity.
Asymmetrical bilinear systems, with different stiffness and damping values for compression and tension, are used when the relative motion in negative direction is more (or less) critical than in positive direction. Sensitivity analysis of the system shows that the difference in the damping plays a more important role than the stiffness difference in these systems.
In this paper, using averaging method, we examine the nonlinear behavior of piecewise linear mounts at resonance, and provide a comprehensive analysis which may be used to better design for these kind of vibration isolators.
Semi-Discretization of Delayed Dynamical Systems
Authors: Insperger Tamás , Stépán Gábor 
Published: November 2020

Abstract
An efficient numerical method is presented for the stability analysis of linear retarded dynamical systems. The method is based on a special kind of discretization technique with respect to the past effect only. The resulting approximate system is delayed and time-periodic in the same time, but still, it can be transformed analytically into a high dimensional linear discrete system. The method is especially efficient for time varying delayed systems, including the case when the time delay itself varies in time. The method is applied to determine the stability charts of the delayed Mathieu equation with damping.
Analysis of Bifurcations and Chaos in Three Coupled Physical Pendulums With Impacts
Authors: Awrejcewicz Jan , Kudra Grzegorz , Lamarque C.-H. 
Published: November 2020

Abstract
In this work the triple pendulum with damping, external forcing and with impacts is investigated. The extension of a coefficient restitution rule and a special transition condition rule for perturbation (linearized system in the Lyapunov exponents algorithm) in each discontinuity point are applied. Periodic, quasi-periodic, chaotic and hyperchaotic motions are observed using Poincaré maps and bifurcational diagrams, which are verified by the Lyapunov exponents. In additon basins of attraction of some coexisting regular and irregular attractors are illustrated and discussed.
Application of the Harmonic Balance Method to Ground Moling Machines Operating in Periodic Regimes
Authors: Woo Ko-Choong , Rodger Albert A. , Neilson Richard D. , Wiercigroch Marian 
Published: November 2020

Abstract
The paper describes current research into mathematical modelling of a novel vibro-impact ground moling system. Experimental and theoretical studies suggest periodic responses are required to achieve the optimal penetrating conditions for the ground moling process, as this results in reduced soil penetration resistance. Therefore, there is a practical need for a robust and efficient methodology to calculate periodic responses for a wide range of operational parameters. Due to the structural complexity of a real vibro-impact moling system, the dynamic response of an idealised impact oscillator has been investigated in the first instance. This paper presents a detailed study of periodic responses of the impact oscillator under harmonic forcing using alternating frequency-time harmonic balance method. Recommendations of how to effectively adapt the alternating frequency-time harmonic balance method for a stiff impacting system are given. The periodic motion is represented algebraically by a truncated Fourier series and the systematic methodology employed allows for convergence. The idea central to this procedure is that the linear oscillator is explicitly solvable analytically, and this allows for the initial set of Fourier coefficients. The clearance value is then adjusted so that contact with the secondary stiffness is slight and the nonlinearity is weak. The solution to this subsequent system is obtainable as the initial guess is close to the required solution.
Periodic and Nonperiodic Thermomechanical Responses of Shape-Memory Oscillators
Authors: Lacarbonara Walter , Bernardini Davide , Vestroni Fabrizio 
Published: November 2020

Abstract
Nonlinear responses of shape-memory oscillators are investigated systematically using a numerical procedure and a modified Ivshin-Pence model for the restoring force. Due to the discontinuities in the tangent stiffness, classical gradient-based shooting techniques for determining periodic responses are not applicable. Herein the implemented algorithm searches the periodic solutions as fixed points of the Poincaré map. The Jacobian of the map is calculated via a central finite-difference scheme and its eigenvalues are computed to ascertain the stability of the solutions and the associated codimension-one bifurcations. A number of frequency-response curves are constructed for some meaningful shape-memory oscillators (characterized by different hysteresis loops) and for various excitation levels in the primary and superharmonic frequency ranges. The investigations are conducted both in isothermal and non-isothermal conditions. A rich class of solutions and bifurcations — including jump phenomena, pitchfork, period doubling, complete or incomplete bubble structures with a variety of nonperiodic responses — is found and discussed.
Analysis of Piecewise Linear Systems With Boundaries in Displacement and Velocity Using Vector Fields
Authors: Nakai Mikio , Hagio Seiji , Mizutani Kazuki , Zahid Hossain Md. 
Published: November 2020

Abstract
A generalized solution methodology based on piecewise linear vector fields has been proposed for piecewise linear systems with boundaries for both displacement and time. In this paper, this methodology is applied in analyzing dynamic responses of torsional vibration through bilinear spring stiffness with changing hysteretic torque in the rotating machinery system, which has boundaries for both displacement and velocity. For asymmetric torque with hysteresis, two cases exist when restoring torque changes smoothly and discontinuously. Period-one and period-two solutions are sought in two cases and compared with ones obtained by the numerical method. Our present method can be applied to dynamic responses of piecewise linear systems having velocity and displacement boundaries.
Experimental Investigation of Control Logic for State-Switched Dampers
Authors: Larson Gregg D. , Cunefare Kenneth A. 
Published: November 2020

Abstract
Recently, significant interest has been generated by the possibilities of active vibration control through the implementation of state switching, or piezoceramic shunting. A state-switched absorber (SSA) is a vibration absorber that has the unique ability to change its resonant state amongst multiple distinct resonant states while in motion, thereby increasing the effective bandwidth over that of a single frequency device and allowing control of multi-frequency and transient disturbances. In contrast, a switch-shunted damper (SSD) is a variant of an SSA that is used to increase the damping of the structure to which the damper is applied. A prototype SSD has been built and tested to experimentally investigate switching control logic. For this prototype, the results indicate that switching states at a condition of maximum strain yields enhanced damping effectiveness but also leads to the generation of potentially undesirable mechanical transients.
Constrained-Layer Damping of Torsional Vibration of Thin-Walled Tubes
Authors: Nayfeh Samir A. 
Published: November 2020

Abstract
In this paper, we take up the problem of damping torsional vibration of thin-walled tubes with closed sections. Assuming that the deformation obeys the Saint-Venant hypotheses, we develop a model suitable for predicting the complex stiffness per unit length in tubes with constrained viscoelastic layers over part or all of their perimeter. For some basic cross-sectional shapes, we solve the warping problem and thence obtain closed-form expressions for the complex stiffness per unit length. Finally, we provide some guidelines for the design of tubes with high damping in torsion.
Vibration Confinement via Optimal Eigenvector Assignment and Piezoelectric Networks
Authors: Tang J. , Wang K. W. 
Published: November 2020

Abstract
The underlying principle for vibration confinement is to alter the structural modes so that the corresponding modal components have much smaller amplitude in concerned areas than the remaining part of the structure. In this research, the state-of-the-art in vibration confinement technique is advanced in two correlated ways. First, a new eigenstructure assignment algorithm is developed to more directly suppress vibration in regions of interest. This algorithm is featured by the optimal selection of achievable eigenvectors that minimizes the eigenvector components at concerned areas by using the Rayleigh Principle. Second, the active control input is applied through an active-passive hybrid piezoelectric network. With the introduction of circuitry elements, which is much easier to implement than changing or adding mechanical components, the state matrices can be reformed and the design space in eigenstructure assignment can be greatly enlarged. The merit of the proposed system and scheme is demonstrated and analyzed using a numerical example.
Modal Control for Piezo-Coupled Elastic Beams and Plates
Authors: Murray John J. , Knowles Gareth J. 
Published: November 2020

Abstract
The potential advantages of lightweight, compact and easily attacheable or embeddable induced strain actuators can be quickly overshadowed by the bulky power supplies, electronics and controls necessary to drive them. Previous work in power and control has used circuit-theoretic concepts to combine the control system design process with energy flow analysis. This is extended here to encompass thin plates with multiple attached piezoelectric devices, providing the basis for an integrated theory of high-efficiency active control with piezoelectric elements. A major result is that, while good broadband vibration suppression and damping require active control, this does not imply that the control consumes net energy. In addition to the usual division into passive and active control, therefore, a third possibility of active, zero-energy control (termed quasi-active control) arises.
Vibration Control of Parallel Identical Flexible Structures Using Interactive Force
Authors: Kougo Shigeru , Fujihara Hiroshi , Yoshida Katsuhiko , Tanaka Hiroyuki , Watanabe Toru , Seto Kazuto , Tan Andy C. C. 
Published: November 2020

Abstract
This paper deals with active vibration control of two identical flexible structures arranged in parallel. One of the authors had presented a vibration control mechanism so that two or more structures are connected via non-contact actuators in which one structure is utilized as a reaction wall for another structure’s control mutually. However, in such a mechanism, the control performance reduces as the natural frequencies of structures become closer. In this report, authors present a modified mechanism in which actuators are connected to the structures with long arms so that the direction of vibration in a mode differs on each structure. In this way, the reaction force from the actuator on structure is introduced to another structure for dissipative force even if the properties of structures are identical. Computer simulation and control experiment are carried out and the effectiveness of presented mechanism is confirmed.
Two-Mode Resonator and Contact Model for Standing Wave Piezomotor
Authors: Andersen Brian , Blanke Mogens , Helbo Jan 
Published: November 2020

Abstract
The paper presents a model for a standing wave piezoelectric motor with a two bending mode resonator. The resonator is modelled using Hamilton’s principle and the Rayleigh-Ritz method. The contact is modelled using the Lagrange Multiplier method under the assumption of slip and it is shown how to solve the set of differential-algebraic equations. Detailed simulations show resonance frequencies as function of the piezoelement’s position, tip trajectories and contact forces. The paper demonstrates that contact stiffness and stick should be included in such a model to obtain physically realistic results and a method to include stick is suggested.