Active Structural Acoustic Control Research Articles

Design of Shaped PVDF Radiation Mode Sensor and its Application in Active Structural Acoustic Control System

This paper presents a new strategy for the design of radiation mode sensors by using shaped PVDF films for one-dimension structures. Based on a modal approach, the shape of a PVDF sensor is analytically determined in such a way that the output signal of the sensor is directly proportional to amplitude of a particular radiation mode. Other modes are filtered out. A general expression of the PVDF sensor shape is obtained. It is found that the modal sensor shape can be expressed as a function of the second spatial derivative of the structural mode shape function. Finally, with an example of a vibrating beam, the proposed PVDF radiation mode sensor is used in an active structural acoustic control system for reduction of the structural-borne noise.

Active Structural-Acoustic Control of Laminated Composite Truncated Conical Shells Using Smart Damping Treatment

This article deals with the active structural-acoustic control of composite truncated circular conical shells using active constrained layer damping (ACLD) treatment. The constraining layer of the ACLD treatment is made of vertically/obliquely reinforced 1–3 piezoelectric composite (PZC) material. A finite element model of smart laminated truncated conical shells backed by the acoustic cavity and integrated with the patches of such ACLD treatment has been developed to demonstrate the performance of these patches for active structural-acoustic control of symmetric and antisymmetric cross-ply and antisymmetric angle-ply truncated conical laminated shells. Both velocity and pressure rate feedback control laws have been implemented to activate the patches. Particular emphasis has also been placed on investigating the effect of variation of piezoelectric fiber orientation angle in the constraining layer on the performance of the patches.

Active Structural Acoustic Control Technology of Enclosure Based on a Multi-agent System

Active Structural Acoustic Control Technology of Enclosure Based on a Multi-agent System

Enclosure Active Structure Acoustic Control Based on Multi-Agent System

For enclosure noise reduction, limited discrete distributed control is an ideal choice when it is difficult to understand sound-structure coupling characteristics accurately. An enclosure medel of two flexible plates is established in this paper. Two secondary control channels are constructed by applying distributed force on flexible plate. In the basis of control problem decomposition a multi-agent system (MAS) structure is established and the coordination relationship between agents is regulated. The simulaition resultes show the Active Structure Acoustic Control based on MAS is effective. The MAS control method improves the extension of noise control system and can be used in “plug-and–play” control field to realize noise reduction. MAS is a better effective tool to realize the divide-and-conquer approach in enclosure noise control field.

Robust μ-Synthesis Control for Parameter Variations

The robust ASAC(active structure acoustic control) model for the system of structural acoustical coupling is established and the μ-synthesis design is presented in the paper. The main idea is as follows: First, the robust performance problem of this system is transformed into the robust stability problem of an augmented system. Through the robust stability controller for this augmented system is solved by the standard D-K iteration. Simulation results show that μ-controller can provide good disturbance rejection and is more robust to parameter variations.

Development of a pseudo-uniform structural quantity for use in active structural acoustic control of simply supported plates: An analytical comparison

Active structural acoustic control has been an area of research and development for over two decades with an interest in searching for an "optimal" error quantity. Current error quantities typically require the use of either a large number of transducers distributed across the entire structure, or a distributed shaped sensor, such as polyvinylidene difluoride. The purpose of this paper is to investigate a control objective function for flat, simply-supported plates that is based on transverse and angular velocity components combined into a single composite structural velocity quantity, termed V(comp). Although multiple transducers are used, they are concentrated at a single location to eliminate the need for transducers spanning most or all of the structure. When used as the objective function in an active control situation, squared V(comp) attenuates the acoustic radiation over a large range of frequencies. The control of squared V(comp) is compared to other objective functions including squared velocity, volume velocity, and acoustic energy density. The analysis presented indicates that benefits of this objective function include control of radiation from numerous structural modes, control largely independent of sensor location, and need to measure V(comp) at a single location and not distributed measurements across the entire structure.

Comparative analysis on acoustic radiation modes of typical structures

Acoustic radiation modes have received increasing attention in the areas of structural acoustic radiation and active structural acoustic control during the past few years. In this paper, a comparative study on the acoustic radiation modes of several typical structures and their associated radiation efficiencies is presented. The present work is also undertaken to extend the acoustic radiation modes into more complex structures, i.e. a thin cylindrical shell, since it was rare described in the literatures. The two analytic approaches for deriving acoustic radiation modes are reviewed briefly first. Numerical examples and comparative analysis are performed from one-dimensional problem to two-dimensional and three-dimensional problems. A grouping characteristic of acoustic radiation modes and their corresponding radiation efficiencies is observed. The shapes of the acoustic radiation modes follow the order of uniform variation, linear, quadratic and high-order variation. It is interesting that the acoustic radiation modes of a cylindrical shell exhibit symmetric and anti-symmetric shapes in the circumferential direction, similarly to its structural modes.

The quiet office—noise abatement in office buildings by means of smart structures

Noise is a serious form of environmental pollution believed to affect the lives of some 100 million European citizens. The cost of the associated damage is estimated at more than ten billion euro per year. Noise leads to serious health problems, limits the capability to learn and effects the occupant comfort and performance in buildings. In this context, advanced noise abatement concepts are being developed in the demonstration project “Quiet Office” within the LOEWE-Center AdRIA (Adaptronics – Research, Innovation, Application), a large interdisciplinary research project funded by the German federal state of Hessia. As underlying principle for noise reduction concepts, Active Structural Acoustic Control (ASAC) is primarily being considered. Applying ASAC concepts, the noise radiation is controlled either by controlling the structural vibration of the radiating structure or by controlling the structure borne sound path. This paper will present the most recent concepts and results from the “Quiet Office”. Starting from more generic concepts, concepts specifically designed for office applications including smart windows will be discussed. Examples presented will include distributed absorbers, shunt technologies with piezoelectric ceramics, smart Helmholtz resonators and fully active noise and vibration control.

Experimental investigation of different active noise control concepts applied to a passenger car equipped with an active windshield

The main purpose of this work is the implementation and experimental investigation of different active structural acoustic control (ASAC) concepts for the reduction of interior noise in an automobile passenger compartment. For the control experiments, a medium-class test car was used, which had been equipped with an active windshield. The active windshield consists of the serial-production laminated glass pane augmented with piezoceramic patch-transducers applied to the blackened rim of the windshield. A multi-reference test provided measurement data for the identification of a local discrete-time state-space model (SSM). The subsequent acquisition of frequency response functions (FRF) by way of using the same actuators but measuring on a much finer grid provided the database for the formulation of a least-squares problem to derive a global system model. Based on the local and global discrete-time SSMs, different controllers were designed and experimentally realized. The comparison of the vibration levels in open- and closed-loop showed a global reduction of 5–7dB in the acoustically relevant frequency band containing the second and third structural resonance of the windshield system. The occurrence of complex operational deflection shapes (ODS) was identified as the main limitation concerning the disturbance rejection of the active system. The acoustic performance of the ASAC system is reflected in a reduction up to 15dB in sound pressure level (SPL).

Study on Vibration Modes and Acoustic Radiation Modes for Air Conditioning Compressor

Vibration and radiated sound of Air Conditioning are harmful to environment and safeness. Air Conditioning Compressor is its major part bringing vibration. To lower noise of a compressor and to improve its sound characteristic, the paper probes into a method indirect measurement of vibration, which both vibration and radiation behavior is represented using acoustic signal and theory of radiation modes. The paper investigates on the basic coupling relationship between structural vibration and acoustic radiation by means of the real modal analysis theory. Besides, the vibration and acoustic radiation characteristics of the rotary compressor are identified through the experiment method. According to the experimental results, between the vibration modes and the acoustic radiation modes have the comparability about the parameters. Therefore, this paper put forward a new method to the Active Structural Acoustic Control (ASAC), and provides the theoretical foundation of indirect measurement of vibration by using acoustic signal.

Error Sensing Strategy for Active Structural Acoustic Control Based on Acoustic Radiation Modes

A new sensing strategy based on acoustic radiation modes for active structural acoustic control approach is proposed for the minimization of the acoustic radiation from a vibrating simply supported plate. Measuring a few points velocity on the vibrating surface and solving the underdetermined equations of the radiation mode expansion, the approximate values of amplitudes of the first radiation modes can be obtained. Taking the above approximate amplitudes as the input signals of the controller, this forms an error sensing strategy based on radiation modes and corresponding active control strategy. The numerical simulations results are presented to show the feasibility of this error sensing strategy.

Active Control of Sound Radiated by a Submarine Hull in Bending Vibration Using Inertial Actuators

Submarines are efficient sources of low frequency radiated noise due to the vibrations induced by the rotation of the propeller in a non uniform wake. In this work the possibility of using inertial actuators to reduce the far field sound pressure is investigated. The submerged vessel is modelled as a cylindrical shell with two conical end caps. Complicating effects such as ring stiffeners, bulkheads and the fluid loading are taken into account. A harmonic radial force is transmitted from the propeller to the hull through the stern end cone and it is tonal at the blade passing frequency (rotational speed of the shaft multiplied by the number of blades). The actuators are attached at the inside of the prow end cone to form a circumferential array. Both Active Vibration Control (AVC) and Active Structural Acoustic Control (ASAC) are analysed and it is shown that the inertial actuators can significantly reduce the far field sound pressure.

Active control of structurally radiated sound from an elastic cylindrical shell

A numerical and experimental study was presented on active control of structurally radiated sound from an elastic cylindrical shell. An analytical model was developed for the active structural acoustic control (ASAC) of the cylindrical shell. Both global and local control strategies were considered. The optimal control forces corresponding to each control strategy were obtained by using the linear quadratic optimal control theory. Numerical simulations were performed to examine and analyze the control performance under different control strategies. The results show that global sound attenuation of the cylindrical shell at resonance frequencies can be achieved by using point force as the control input of the ASAC system. Better control performance can be obtained under the control strategy of minimization of the radiated sound power. However, control spillover may occur at off-resonance frequencies with the control strategy of structural kinetic energy minimization in terms of the radiated sound power. Considerable levels of global sound attenuation can also be achieved in the on-resonance cases with the local control strategy, i.e., minimization of the mean-square velocity of finite discrete locations. An ASAC experiment using an FXLMS algorithm was implemented, agreement was observed between the numerical and experimental results, and successful attenuation of structural vibration and radiated sound was achieved.

Coupling Acoustic Analysis of Enclosure Consisting of Multi-Flexible Plates and its Active Structural Acoustic Control

This paper develops a model of structural-acoustic coupled system of a rectangular enclosure involving two simply supported flexible plates. The acoustical potential energy and the optimal secondary control forces are derived theoretically. An example is presented to analyze the characteristics of the coupled system, the dominant factors that impact the coupling effects and the noise reduction with ASAC method. The paper shows the possibility of applying distributed cooperative control method to the structural-acoustic coupled system.

Structural Acoustic Reduction via Piezoelectric Actuation and Adaptive Eigenvector Optimization Algorithm

The purpose of this research is to investigate the feasibility of utilizing the adaptive eigenvector optimization algorithm to find the optimal combination of left and right eigenvectors for active structural acoustic reduction. As depicted in the previous studies, the structural acoustic radiation depends on the structural vibration behavior, which is strongly related to the mode shape distributions (represented by the right eigenvectors of system) as well as the ability of disturbance rejection (represented by the left eigenvectors of system). In this research, a novel adaptive optimization algorithm is developed to determine the optimal combination of left and right eigenvectors of the structural system for active structural acoustic control. The sound suppression performance index (SSPI) is defined by combining the orthogonality index of left eigenvectors and the modal radiation index of right eigenvectors. Through the proposed adaptive eigenvector optimization algorithm, both the left and right eigenvectors of the structural system are adjusted such that the SSPI quantity decreases, hence the optimal combination of the corresponding left and right eigenvectors of the closed-loop system can be found for reducing the structural acoustic radiation. The optimal combination of left-right eigenvectors is then synthesized to determine the feedback gain matrix of the closed-loop system. The result of the active acoustic control shows that the proposed method can significantly suppress the sound pressure radiated from the vibrating structure.

Attenuation of Structurally Radiated Sound from an Elastic Cylindrical Shell by Local Vibration Control

This paper presents a numerical and experimental study on attenuation of structurally radiated sound from an elastic cylindrical shell by local vibration control. An analytical model is developed for the active structural acoustic control (ASAC) of the cylindrical shell. A local control strategy is considered by minimization of the mean-square velocity of finite discrete locations. Numerical simulations are performed to examine and analyze the control performance. Results show that global sound attenuation of the cylindrical shell can be obtained at resonance frequencies. However, control spillover may occur at off-resonance frequencies. Modal suppression and rearrangement mechanisms may be involved in the control process. ASAC experiment was implemented by FXLMS algorithm, good agreement was observed between the numerical and experimental results, and successful attenuation of radiated sound was achieved.

Analytical and experimental study on active control of structurally radiated sound from an elastic cylindrical shell.

This paper presents an analytical and experimental study on active control of structurally radiated sound from an elastic cylindrical shell. An analytical model is developed for the active structural acoustic control (ASAC) of the cylindrical shell. The structural response of a cylindrical shell to the harmonic point force is derived by applying the modal supposition method. Expressions for the far-field radiated sound pressure and radiated sound power are derived by using the Kirchhoff–Helmholtz integral and the appropriate Green’s function. Both global and local control strategies are considered. The optimal control forces corresponding to each control strategy are obtained by using the linear quadratic optimal control theory. Numerical simulations are performed to examine and analyze the control performance under different control strategies. Results show that using point force as the control input of the ASAC system can achieve the global sound attenuation of the cylindrical shell at resonance frequencies. Better control performance can be obtained under the control strategy of minimization of the radiated sound power in terms of the radiated sound power. However, control spillover may occur at off-resonance frequencies with the structural kinetic energy minimization strategy. ASAC experiment was implemented, good agreement was observed between the numerical and experimental results, and successful attenuation of structural vibration and radiated sound was achieved.

Active control of sound radiated by a submarine in bending vibration

This paper theoretically investigates the use of inertial actuators to reduce the sound radiated by a submarine hull in bending vibration under harmonic excitation from the propeller. The radial forces from the propeller are tonal at the blade passing frequency and are transmitted to the hull through the stern end cone. The hull is modelled as a fluid loaded cylindrical shell with ring stiffeners and two equally spaced bulkheads. The cylinder is closed by end-plates and conical end caps. The actuators are arranged in circumferential arrays and attached to the prow end cone. Both Active Vibration Control and Active Structural Acoustic Control are analysed. The inertial actuators can provide control forces with a magnitude large enough to reduce the sound radiated by the vibrations of the hull in some frequency ranges.

Modal criteria for optimization of structures through active structural acoustic control

AbstractThis paper deals with modal criteria allowing optimization of structures through active structural acoustic control (ASAC) based on the independent modal strategy control (IMSC). The aim of the paper is to propose efficient criteria allowing to process optimization of structures by determining the most important modes to control considering only the location of the excitation on the structure. A generalized modal synthesis is used to study the coupled fluid–structure system. Modal criteria are proposed in order to determine the best choice for the controlled modes used in IMSC method. The way the ASAC will be applied is not discussed in the paper. Numerical simulations are computed to show the efficiency of the method, considering a simple vibroacoustic structure. Copyright © 2010 John Wiley & Sons, Ltd.

Active structural acoustic control for a truck oil pan: Actuator placement and efficiency estimation

The oil pan of large diesel engine trucks is identified as a significant contributor to their external noise radiation. This undesired broadband noise is caused by the oil pan's structural vibration and cannot be treated effectively by passive measures, especially in the low frequency range up to 500 Hz. In order to address this challenge, an Active Structural Acoustic Control (ASAC) system was to be realized within the European Union (EU) project �Intelligent Materials for Active Noise Reduction� for the oil pan of a Volvo MD13 truck engine. The technological demonstration was conducted in a laboratory test stand and employs piezoceramic patch actuators to alter the vibrations in a broadband noise reduction manner. The following paper focuses on the tasks of deriving actuator placement and estimating respective broadband sound power minimization capability. First, the oil pan's structural response to typical force excitation at its mounting points was analyzed through finite element simulation, and an actuator placement was derived. The estimation of its sound power minimization capability was then established based on computed structural frequency response functions and numerically derived radiation modes. Finally, the actuator layout was transferred to a serial production oil pan and adjusted by experimental observations