Active Wave Control Research Articles

G1000-5-3 Active Boundary Controlを基調とした閉空間場における静粛場生成(機械力学・計測制御部門一般講演(5):音響・波動,社会変革を技術で廻す機械工学)

This paper presents an acitve boundary control (ABC) method of a three dimensional rectangular enclosure and to clarify fundamental properties of the control system. Firstly, a transfer matrix method for the target system is introduced to describe the dynamics in the enclosure. This is followed by the derivation of an active boundary control laws and its comparison with active wave control laws. Then, from a viewpoint of numerical analyses, basic properties of the proposed method is verified. It is found that the proposed method enables the generation of a silent zone

Active wave control and generalized surface potentials

In active wave control, an arbitrary bounded domain with the smooth boundary is shielded from the outside field (noise) using additional sources. Unlike passive control, there is no any mechanical insulation in the system. The general solution of the problem is obtained in unsteady linear formulation. For this purpose, the theory of potentials introduced by Ryaben'kii is extended to initial–boundary value problems and the theory of distributions. Both first- and second-order spatial differentiation operators are considered. The obtained results can immediately be applied to active control problems in electromagnetics and acoustics. Two classical problems, on a bounded conductor in an electrostatic field and superconductor in a magnetostatic field, are interpreted as active control problems. The control sources for aeroacoustics are then obtained in the form of a linear combination of single- and double-layer sources. The constructed solution of the problem requires only the knowledge of the total field on the perimeter of the shielded domain.

Feedforward control of flexural waves propagating in a rectangular panel

This paper is concerned with active wave control of a distributed parameter structure. It is the purpose of this paper to present the active wave control method of a rectangular panel and to clarify fundamental properties of the control system. Firstly, a transfer matrix method for a rectangular panel is introduced to describe the wave dynamics of the structure. This is followed by the derivation of feedforward control laws for absorbing reflected waves or eliminating transmitted waves. In the proposed method, the control laws are including the modal actuation scheme for uncontrolled direction. Then, from a viewpoint of numerical analyses, basic properties of the proposed method are verified. It is found that the reflected wave absorbing control enables the inactivation of all vibration modes in the controlled direction and the transmitted wave eliminating control enables the generation of an almost vibration-free state. It is also found that some phenomena different from the case of a beam-like structure appear under certain boundary conditions.

波動制御理論を基調とした直方体閉空間場における静粛化制御に関する研究(機械力学,計測,自動制御)

This paper is concerned with an active noise control for an enclosed sound field. It is the purpose of this paper to present an active wave control method of a three dimensional rectangular enclosure and to clarify fundamental properties of the control system. Firstly, a transfer matrix method for the target system is newly introduced to describe the wave dynamics in the enclosure. This is followed by the deriviation of feedforward control laws for absorbing reflected waves or eliminating transmitted waves. In the proposed method, the control laws are including the modal actuation scheme for uncontrolled direction. Then, from a viewpoint of numerical analyses, basic properties of the proposed method is verified. It is found that the transmitted wave eliminating control enables the generation of silent zone, and the reflected wave absorbing control enables the inactivation of acoustical modes in the controlled direction.

Active Wave Control of String Near Fixed Boundary

Abstract We studied a wave control of a string near a fixed end. The equation of motion of a string is approximated as a lumped-parameter spring-and-mass system using the finite difference method. Finite difference equations (FDEs) for interior node points have the same set of coefficients, whereas the FDEs for boundary node points have a different set of coefficients. By using the control, the latter equation is modified to be as the same equation as the former one. The propagating wave is absorbed through a control actuator as if no boundary existed, and virtually, an infinite system is thus realized. Control is at the string position of the finite difference mesh spacing inside the fixed boundary that is free from supporting loads. We confirmed the effectiveness of the controller by numerical simulation for the traveling string and also did that by numerical simulation and by an experiment for the nontraveling string.

An experimental study of flow induced vibration on a tensioned membrane

In pursuing noise and wave control with minimal aerodynamic or hydrodynamic sacrifice, a tensioned membrane is used to line the otherwise rigid duct wall. The membrane vibrates in response to the grazing incident waves and the vibration serves to reflect the wave towards its source. The mechanism is identical to what happens in a rig of active wave control, but the difference is that the current rig has no active component. For the purpose of wave control, the device has been tested successfully without flow and with moderate flow conditions commonly found in air ventilation systems. When the flow speed is further increased, flow induced vibration occurs. This study reports the phenomena of such vibration under various flow speeds and membrane tensions. Transient process of exponential vibration growth is recorded and analysed together with the boundary layer measurements. The effects of an external cavity as well as the lateral membrane tension are also found to be significant. Other possible mechanisms for the flow induced vibration are also explored and discussed.

429 薄肉矩形平板構造物におけるフィードフィワード型波動制御に関する研究

This paper considers an active wave control of a rectangular panel. It is the purpose of this paper to expand the active wave control method of a one-dimensional structure for a two-dimensional structure case and to clarify fundamental properties of the control system. Firstly, a transfer matrix method for a rectangular panel is introduced to describe the wave dynamics of the structure. This is followed by the derivation of feedforward control laws for absorbing reflected waves or eliminating transmitted waves. Then, from a viewpoint of numerical analyses, basic properties of the proposed method are verified. It is found that the reflected wave absorbing control enables the inactivation of all vibration modes, and the transmitted wave eliminating control enables the generation of an almost vibration-free state.

Active Wave Feedback Control at a Free End of a Flexible Beam Using a Wave Filter Constructed with Point Sensors (Theoretical Verification of Basic Properties)

This paper deals with the feedback wave control of a flexible beam using the wave filter constructed with four point sensors. The objective of this paper is to theoretically lay out the active wave control at free end of the beam which is independent of the disturbance positions. Firstly, the transfer matrix method and wave filtering method are extended to the Laplace domain. Next, based on the relation between the incident and reflected wave vectors at a free end, the control laws and characteristic equation of the control system are derived. Moreover, the control effects are presented from a viewpoint of a numerical analysis. It is found that the proposed method can eliminate the designated wave even if a disturbance acts around the control point. Finally, the stability of the control system is clarified by using root loci, showing that all poles are close to the critical damping.

Cluster power flow control of a distributed-parameter planar structure for generating avibration-free zone

To generate a vibration-free zone in a designated region of a structure, cluster power flowcontrol is presented. Unlike conventional modal-based vibration control, mainlyused for augmenting structural damping, active wave control can render all thevibration modes inactive; the gain characteristic of a forced vibration responseconverges to the asymptote—to a far greater extent than augmenting structuraldamping; however, progressive waves still remain. Power flow control, advancedactive wave control, allows the generation of a vibration-free zone when properlyconfigured to handle all the governing structural variables. To implement power flowcontrol, cluster control is introduced, which guarantees unconditional stability of afeedback system. To evaluate the vibration-free state, a vibration intensity isintroduced; however, as a result of suppressing the vibration intensity, two extremephenomena arise: suppression or excitation of structural modes. To overcomethis problem, minimization of the dominant structural variables that are thecounterparts of the vibration intensity elements is set up, with the result that avibration-free zone is generated, together with the suppression of the vibrationintensity. A numerical analysis is then conducted, followed by an experiment,demonstrating the capability of the proposed method for generating a vibration-free zone.

Adaptive feed-forward control of flexural waves propagating in a beam using smartsensors

This paper concerns the active vibration control of a flexible beam using smart sensorsfrom the viewpoint of an active wave control theory. The objective of this paper is topresent a new type of sensor which enables one to measure the wave amplitude of a flexiblebeam in real time for the application of use in an adaptive feed-forward controlsystem. Firstly, a novel wave filtering method using distributed parameter PVDFsensors is proposed. It integrates an infinite number of point sensors and has anintegral calculation ability based on a proposed shaping function. Furthermore, thecharacteristics of the wave filter and the performance of the adaptive feed-forward controlsystem using the wave filter are discussed. Finally, experiments adopting the activewave control theory which use the wave filter are conducted, demonstrating thevalidity of the proposed method in suppressing the vibration of a flexible beam.

Active Power Flow Control of a Flexible Beam (Generation of a Quiet Zone by Using Vibration Intensity Suppression)

This paper addresses the active power flow control of a flexible beam. Unlike conventional modal-based vibration control, power flow control falling into a category of active wave control has the potential for suppressing all the vibration modes of a target structure. From a viewpoint of wave propagation, this paper presents a novel power flow control using vibration intensity as a criterion of vibration energy flow. By expanding the conception of the approach presented in the work, a control method to generate a quiet zone on a designated area of the target beam is then proposed. Finally, a numerical simulation as well as an experiment using adaptive feedforward control was conducted, demonstrating the validity of the proposed active power flow control.

Active Wave Feedforward Control of a Flexible Beam Using Smart Sensors

This paper deals with active wave control of a flexible beam using a wave filter constructed with smart sensors. It is the purpose of this paper to present a novel wave filtering method using PVDF film sensor and its application for adaptive feedforward control system. Firstly, the design procedure of the wave filter using shaped PVDF sensors is presented. When introducing PVDF sensor, shaping function is defined as a complex function. In this case, multiplying an imaginary unit is equivalent to making the phase difference of 90 degree. Next, from a viewpoint of numerical analysis, the accuracy of the wave filter and the performance of the control system is clarified. Finally, an experiment of the active wave feedforward control system is carried out, demonstrating the validity of the proposed method.

Active Power Flow Control of a Thin Plate(Generation of a Quiet Zone by Using Vibration Intensity Suppression)

This paper addresses the active power flow control of a vibrating plate. Unlike conventional modal-based vibration control, power flow control falling into a category of active wave control has the potential for suppressing all the vibration modes of a target structure. From a viewpoint of wave propagation, this paper pressents a novel power flow control using vibration intensity as a criterion of vibration energy flow. By expanding the conception of the approach presented in the work, a control method to generate a quiet zone on a designated area of the target plate is then proposed. Finally, a numerical simulation as well as an experiment using adaptive feedforward control was conducted, demonstrating the validity of the proposed active power flow control.

Active Vibration Control Methods of Axially Moving Materials - A Review

In this paper we provide a review of the state of the art for active vibration control of axially moving materials (string and beam, etc.) in the past ten years, with particular regard to the subjects of some important active control methods of axially moving strings. First, an introduction is given to explain the aims and scope of this paper. This is followed by a comprehensive discussion of the active wave control methods presented by many investigators in the past ten years, including feedback control methods (such as the modal control method, the direct velocity feedback control method and the control method via transfer function formulation), active wave control methods combining transfer function, boundary control methods using the Lyapunov function, the variable structure control method, the adaptive control method, the vibration control of an axially moving beam and the active control of a moving material with arbitrarily varying length, etc. Finally, we conclude with a discussion of several issues for future research in this area.

Active Wave Feedback Control of a Flexible Beam Using Wave Filter (Theoretical Verification of Basic Properties)

This paper deals with the active wave control of a flexible beam using wave filter which enables the direct sensing of a designated wave amplitude. It is the purpose of this paper to present the basic properties of active wave feedback control system based upon wave amplitude signal. First, the state equation of a flexible beam with arbitrary boundary condition is described by using a transfer matrix method. Then, two kinds of control laws are derived; one is for absorbing reflected wave and the other is for eliminating transmitted wave. Next, from a viewpoint of numerical analysis, the basic properties of control laws and its control effects are investigated. Finally, an active wave control system is found to be stable regardless of whether collocation holds or not, demonstrating the relation of stability between control and measurement point placement.

Active Wave Feedforward Control of a Flexible Beam Using Wave Filter Constructed with Point Sensors

This paper deals with the active wave control of a flexible beam using the wave filter constructed with four point sensors. It is the purpose of this paper to verify the active wave control system with adaptive feedforward technique. Firstly, the active sink method is introduced which is useful as a performance index of active wave control method. If the active sink system is constructed, all vibration modes are made inactive (more than suppressed), and its frequency characteristics are similar to the one of semi-infinite beam. Next, the design procedure of the wave filter using four point sensor is presented, its realization also being presented. Finally, experiment of the active wave feedforward control system is carried out, demonstrating the validity of the proposed method and the robustness against the sensor placement.

Active Progressive Wave Control of a Simply Supported Plate

This paper deals with the active control of progressive wave of a simply supported, lossless, thin distributed-parameter planar structure. It is the purpose of this paper to present a novel active wave control method for blocking the progressive wave, and thus a quiet zone (a specific region where vibration is to be prohibited) is produced. It is also the purpose of this paper to present a means to visualize wave propagation of the structure, whereby control effect for suppressing power flow in terms of vibration intensity, progressive wave, reflected wave and the combination of thereof becomes evident.

ACTIVE WAVE CONTROL OF A FLEXIBLE BEAM USING DISTRIBUTED PARAMETER SENSORS

This paper considers the active vibration control of a flexible beam using distributed parameter sensors from the viewpoint of active wave control theory. It is the pupose of this paper to present a new type of sensor which makes it possible to measure waves amplitude of a flexible beam in real time fore the application of the adaptive feedforward control system. Firstly, a novel wave filtering method using distributed parameter PVDF sensors is proposed which can be regarded as the integration of infinite point sensors, and have arithmetic calculation by being shaped on the basis of arbitrary functions. Furthermore, the characteristics of the wave filter are clarified. Finally, experiments on active wave control using the wave filter are conducted, and the control effects for suppressing the vibration of a targeted frequency are presented.

Active Progressive Wave Control of a Simply Supported Plate.

Active Progressive Wave Control of a Simply Supported Plate.

ACTIVE PROGRESSIVE WAVE CONTROL OF A SIMPLY SUPPORTED PLATE

This paper deals with the active control of progressive waves of a simply supported, lossless, thin distributed-parameter planar structure. It is the purpose of this paper to present a novel active wave control method for blocking the progressive wave, and thus a quiet zone (a specific region where vibration is to be prohibited) is produced. It is also the purpose of this paper to present a means to visualize wave propagation of the structure, whereby control effect for suppressing power flow in terms of vibration intensity, progressive waves, reflected waves and the combination of thereof becomes evident.