A state feedback electro-acoustic transducer for active control of acoustic impedance

2003 ◽  
Vol 113 (3) ◽  
pp. 1483-1491 ◽  
Author(s):  
Toshiya Samejima
Keyword(s):  
Active Control ◽  
Acoustic Impedance ◽  
State Feedback ◽  
Acoustic Transducer

Classification of Iron Meteorites with High Frequency Ultrasonic Waves

2019 ◽  
Vol 24 (2) ◽  
pp. 277-284
Author(s):  
Dris El Abassi ◽  
Bouazza Faiz ◽  
Abderrahmane Ibhi ◽  
Idris Aboudaoud
Keyword(s):  
Phase Velocity ◽  
Acoustic Impedance ◽  
Nickel Content ◽  
Normal Incidence ◽  
Ultrasonic Pulse ◽  
Ultrasonic Waves ◽  
Iron Meteorites ◽  
Acoustic Transducer ◽  
Pulse Echo ◽  
Non Destructive

We present the results of an ultrasonic pulse-echo technique and its potential to classify iron meteorites into hexahedrites, octahedrites and ataxites by determining their acoustic impedance and phase velocity. Our technique has been adapted from those used in the field of ultrasonic non-destructive investigation of a variety of materials. The main advantage of our technique is that it does not need any preparation of the meteorites like cutting and etching and therefore is rapid, easy and non-destructive. In essence, a broadband acoustic transducer is used in a monostatic pulse-echo configuration which means that both the transducer and the meteorite sample are located in a water bath and adjusted in the way that the ultrasonic pulse shit the meteorite sample at normal incidence. Then the reflected pulses from the front and rear faces of the meteorite sample are measured with the emitting transducer, digitally recorded and processed to analyze the signal. After Fourier transforming the echoed pulses from the front and the rear face of the meteorite sample, the calculated reflection coefficients yield the phase velocity and the acoustic impedance. Our study investigates a variety of iron meteorites collected in Morocco and other countries and it helps to understand how the nickel content of these meteorites affects the acoustic impedance. It reveals that the acoustic impedance of iron meteorites increases with increasing nickel content, so that a further refinement of our technique might have the potential to classify iron meteorites directly and reliably into hexahedrites, octahedrites and ataxites without destroying them.

Active Control of Wall Acoustic Impedance

AIAA Journal ◽  
1999 ◽  
Vol 37 (7) ◽  
pp. 825-831 ◽  
Author(s):  
Hongwu Zhao ◽  
Xiaofeng Sun
Keyword(s):  
Active Control ◽  
Acoustic Impedance

Actively Silencing a Cavity by Acoustic Impedance Changes

1997 ◽  
Author(s):  
O. Lacour ◽  
D. Thenail ◽  
M. A. Galland
Keyword(s):  
Active Control ◽  
Acoustic Impedance ◽  
Fluid Structure Interaction ◽  
Central Point ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Sound Fields ◽  
Source Radiation ◽  
Absorbed Power

Abstract We attempt here the active control of enclosed sound fields via wall impedance changes. The impedance value which is the most efficient in silencing a cavity is the central point of this paper. Simulations and experiments show that the optimal impedance is not necessarily characterized by an large amount of absorbed power. Its silencing effect depends also on its ability to reduce source radiation. Experiments including fluid-structure interaction are also presented.

Fuzzy Modal Active Control of Flexible Structures

2005 ◽  
Vol 11 (1) ◽  
pp. 67-88 ◽  
Author(s):  
M. Malhis ◽  
L. Gaudiller ◽  
J. Der Hagopian
Keyword(s):  
Active Control ◽  
State Feedback ◽  
Flexible Structures ◽  
Element Model ◽  
Transverse Plane ◽  
Digital Controller ◽  
Flexible Beam ◽  
Modal Control ◽  
Modal Reduction ◽  
Active Control Strategy

In this paper we propose a new active control strategy to control the dynamic behavior of flexible structures: fuzzy modal control (FMC). This strategy, based on the modal state feedback of the structure, uses independent fuzzy controllers for each mode to be controlled. This method is applied to a flexible beam controlled by a transverse plane of action using piezoelectric actuators. First of all, a model of a piezoelectric actuator is proposed, followed by the formulation of a finite-element model of the mechanical structure/actuator. The model is then fitted using an identification of the characteristics. After modal reduction, the FMC is carried out in two steps: the control of the beam in only one transverse direction by a piezoelectric pusher, then in two transverse directions by two orthogonal piezoelectric pushers located on the same plane. A digital controller was built in the Matlab®-Simulink® environment, and implemented on specialized cards in order to perform the corresponding experiment. The method is validated by comparing the results between the simulation and the experiment.

Active control of wall acoustic impedance

AIAA Journal ◽  
1999 ◽  
Vol 37 ◽  
pp. 825-831 ◽  
Author(s):  
Hongwu Zhao ◽  
Xiaofeng Sun
Keyword(s):  
Active Control ◽  
Acoustic Impedance

Decentralized vibration control of smart constrained layer damping plate

2020 ◽  
pp. 107754632093164
Author(s):  
Panping Lu ◽  
Pan Wang ◽  
Jun Lu
Keyword(s):  
Active Control ◽  
Thin Plate ◽  
State Feedback ◽  
Control Method ◽  
Feedback Stabilization ◽  
Local State ◽  
System Stability ◽  
Pole Placement ◽  
Periodic Signal ◽  
Constrained Layer Damping

The traditional centralized control strategy to vibration suppression of large-scale thin plate structures may increase the design difficulty of the controller. In this article, a decentralized vibration active control method is proposed to suppress the vibration of the thin plate structure with smart constrained layer damping treatment. First, the dynamics model of the smart constrained layer damping plate is established based on the finite element method, and the characteristics of viscoelastic materials with temperature and frequency are described by Golla-Hughes-McTavish damping model. Subsequently, a decentralized subsystem control model is obtained from the balanced model reduction method and complex mode truncation method. The modal test proves that the theoretical model is accurate. Then, the particular emphasis is placed on the stability and vibration attenuation of a decentralized system, which is composed of multiple subsystems. The local state feedback stabilization, using interaction of local state feedback and output feedback, is introduced to achieve system stability. To solve the practical problem of local state feedback, a decentralized controller with an observer is developed by adopting the pole placement method. Finally, the numerical simulation and hardware-in-the-loop experiment under different excitation are performed to investigate the effectiveness of decentralized vibration active control. The results demonstrate that the decentralized controller can effectively suppress the vibration, especially under mixed periodic signal and Gauss white noise signal.

scholarly journals Active control of acoustic impedance with a multi‐element system

1995 ◽  
Vol 97 (5) ◽  
pp. 3339-3339
Author(s):  
Brian H. Houston ◽  
Douglas M. Photiadis ◽  
J. A. Bucaro ◽  
Robert D. Corsaro ◽  
Larry A. Kraus
Keyword(s):  
Active Control ◽  
Acoustic Impedance ◽  
Element System
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