The purpose of this paper is to discuss a methodology for determining some modal parameters (frequencies, damping ratios, and seismic eigenvectors) and, under certain hypotheses,
the physical matrices of a general structure with proportional damping and subjected to seismic loads. The procedure is based on a time-domain state space formulation from which the
modal parameters, including the seismic eigenvectors, and the complex eigenvectors of the
system can be derived also in the case of a limited set of instrumentations. The conditions to
normalize the eigenvectors are then illustrated and, finally, applied to derive the second-order
matrices of the system. The proposed procedure is applied to some numerical examples also
in the case of noise-polluted measurements and to an experimental investigation performed
on a four-story steel frame subjected to earthquake excitations. An optimization procedure
to improve the prediction of the first-order modal parameters of the system is also discussed
and experimentally proved.

M. De Angelis

M. Imbimbo

A Procedure to Identify the Modal and Physical Parameters of a Classically Damped System under Seismic Motions

This paper proposes different design strategies of robust
controllers for high-order plants. The design is tailored on the
structure of the equations resulting from modeling flexible
structures by using modal coordinates. Moreover, the control laws
have some characteristics which make them specially suited for
active vibration reduction, such as strong stabilization property
and bandpass frequency shape. The approach is also targeted the case
of more sensors than actuators, which is very frequent in practical
applications. Indeed, actuators are often rather heavy and bulky,
while small and light sensors may be placed more freely. In such
cases, sensors can be usefully placed in the locations where the
primary force fields act on the structure, so as to provide the
controller with a direct information on the disturbance effects in
terms of structural vibrations. Eventually, this approach may lead
to uncolocated control strategies. The design problem is here solved
by resorting to a Linear Matrix Inequality technique, which allows
also to select the performance weights based on different design
requirements, for example, a suitable bandpass frequency shape. 
Experimental results are presented for a vibration reduction problem
of a stiffened aeronautical panel controlled by piezoelectric
actuators.

Alberto Cavallo

Giuseppe De Maria

Ciro Natale

Salvatore Pirozzi

Classes of Strongly Stabilizing Bandpass Controllers for Flexible Structures

A <svg style="vertical-align:-0.3135pt;width:32.700001px;" id="M1" height="11.075" version="1.1" viewBox="0 0 32.700001 11.075" width="32.700001"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,11.075)">
		<g transform="translate(72,-63.14)">
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				<tspan style="font-size: 12.50px; " x="0" y="0">4</tspan>
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				<tspan style="font-size: 12.50px; " x="19.804752" y="0">4</tspan>
			</text>

		</g>
	</g>
</svg> matrix model with three degrees of freedom
is proposed as a means for controlling microvibrations and
applied to an electromagnetic isolator. The model was derived
from an assumption based on small- and low-frequency vibrations. 
The coordinates of the 3 DOF was composed of the 4 variables,
representing a vertical position, pitch, roll, and a proof term. 
The coordinates were calculated from the 4 position sensors
in the isolator and formulated into a <svg style="vertical-align:-0.3135pt;width:32.700001px;" id="M2" height="11.075" version="1.1" viewBox="0 0 32.700001 11.075" width="32.700001"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,11.075)">
		<g transform="translate(72,-63.14)">
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				<tspan style="font-size: 12.50px; " x="19.804752" y="0">4</tspan>
			</text>

		</g>
	</g>
</svg> matrix, which
possesses inversive full rank. The electro-magnetic isolator was
built for a simulated machine in semiconductor manufacturing
and consisted of a heavy surface plate, sensors, amps, a controller,
and air springs with electromagnets. The electromagnets are
installed in a pneumatic chamber of the individual air spring. 
The performance of the 3 DOF model was experimented and
compared with that of a 1 DOF model in an impact test. The
settling time in the result was reduced to 25&#x25;.

HyungTae Kim

CheolHo Kim

SungBok Kang

KangWon Lee

JaeHo Baek

HyunHee Han

A 3 DOF Model for an Electromagnetic Air Mount

Machine condition monitoring and diagnosis have become increasingly important, and the application of these processes has been widely investigated. The authors previously proposed a stepwise diagnosis method for a beam structure. In that method, the location of the abnormality is first estimated using the force identification approach, and then the cause of the abnormality is identified. In this study, the stepwise diagnosis method was improved specifically for rotating machinery. The applicability of the proposed method was checked by using the experimental data. In the case of a rotor system with unbalance, it was shown that the location of the abnormality and its severity could be identified, and, in the case of a rotor system with stationary rubbing, the location of the abnormality could be accurately identified. Therefore, it was confirmed that the proposed diagnostic method is feasible for actual application.

Shozo Kawamura

Kazuhiro Niimi

Yuichi Kato

Hirofumi Minamoto

Stepwise Diagnosis for Rotating Machinery Using Force Identification Approach

This paper presents a variational formulation for the free vibration analysis of unsymmetrically laminated composite plates with elastically restrained edges. The study includes a micromechanics approach that allows starting the study considering each layer as constituted by long unidirectional fibers in a continuous matrix. The Mori-Tanaka method is used to predict the mechanical properties of each lamina as a function of the elastic properties of the components and of the fiber volume fraction. The resulting mechanical properties for each lamina are included in a general Ritz formulation developed to analyze the free vibration response of thick laminated anisotropic plates resting on elastic supports. Comprehensive numerical examples are computed to validate the present method, and the effects of the different mechanical and geometrical parameters on the dynamical behavior of different laminated plates are shown. New results for general unsymmetrical laminates with elastically restrained edges are also presented. The analytical approximate solution obtained in this paper can also be useful as a basis to deal with optimization problems under, for instance, frequency constraints.

Liz G. Nallim

Facundo J. Bellomo

Ricardo D. Quinteros

Sergio Oller

Dynamical Analysis of Long Fiber-Reinforced Laminated Plates with Elastically Restrained Edges

Because of the density mismatch between the decoupler and surrounding fluid, the decoupler of all hydraulic engine mounts (HEM) might float, sink, or stick to the cage bounds, assuming static conditions. The problem appears in the transient response of a bottomed-up floating decoupler hydraulic engine mount. To overcome the bottomed-up problem, a suspended decoupler design for improved decoupler control is introduced. The new design does not noticeably affect the mechanism's steady-state behavior, but improves start-up and transient response. Additionally, the decoupler mechanism is incorporated into a smaller, lighter, yet more tunable and hence more effective hydraulic mount design. The steady-state response of a dimensionless model of the mount is examined utilizing the averaging perturbation method applied to a set of second-order nonlinear ordinary differential equations. It is shown that the frequency responses of the floating and suspended decoupled designs are similar and functional. To have a more realistic modeling, utilizing nonlinear finite elements in conjunction with a lumped parameter modeling approach, we evaluate the nonlinear resorting characteristics of the components and implement them in the equations of motion.

J. Christopherson

M. Mahinfalah

Reza N. Jazar

Suspended Decoupler: A New Design of Hydraulic Engine Mount

The effect of a high-frequency excitation on nontrivial solutions and bistability in a delayed Duffing oscillator with a delayed displacement feedback is investigated in this paper. We use the technique of direct partition of motion and the multiple scales method to obtain the slow dynamic of the system and its slow flow. The analysis of the slow flow provides approximations of the Hopf and secondary Hopf bifurcation curves. As a result, this study shows that increasing the delay gain, the system undergoes a secondary Hopf bifurcation. Further, it is indicated that as the frequency of the excitation is increased, the Hopf and secondary Hopf bifurcation curves overlap giving birth in the parameter space to small regions of bistability where a stable trivial steady state and a stable limit cycle coexist. Numerical simulations are carried out to validate the analytical finding.

Mustapha Hamdi

Mohamed Belhaq

Control of Bistability in a Delayed Duffing Oscillator

The static stability of an asymmetric, rotating sandwich beam subjected to an axial pulsating load has been investigated for pinned-pinned and fixed-free boundary conditions. The equations of motion and associated boundary conditions have been obtained by using the Hamilton&#39;s energy principle. Then, these equations of motion and the associated boundary conditions have been nondimensionalised. A set of Hill&#39;s equations are obtained from the nondimensional equations of motion by the application of the general Galerkin method. The static buckling loads have been obtained from Hill&#39;s equations. The influences of geometric parameters and rotation parameters on the nondimensional static buckling loads have been investigated.

P. R. Dash

K. Ray

S. K. Sarangi

P. K. Pradhan

Analysis of Static Instability of an Asymmetric, Rotating Sand-Wich Beam

It is shown that the alternate passivity-based control schemes can be designed which explicitly exploit the passivity properties of the Timoshenko model. This approach has the advantage over the conventional methods in the respect that it allows one to deal directly with the system&#39;s partial differential equations without resorting to approximations. Numerical results for the tracking control of a translational and rotational flexible Timoshenko arm are presented and compared. They verify that the proposed control schemes are effective at controlling flexible dynamical systems.

Minoru Sasaki

Takeshi Ueda

Yshihiro Inoue

Wayne J. Book

Passivity-Based Control of Rotational and Translational Timoshenko Arms

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<p><em>Advances in Acoustics and Vibration</em> acts as a forum for the dissemination of innovative and original research and development work in the area of acoustics and vibration.</p>


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Advances in Acoustics and Vibration ceased publication in 2019 and is no longer accepting submissions.

description

Advances in Acoustics and Vibration acts as a forum for the dissemination of innovative and original research and development work in the area of acoustics and vibration.

Advances in Acoustics and Vibration