Abstract In the authors’ previous report, a new piezoelectric cylindrical shell wind power generation flag had been proposed as a flexible and durable power generation structure that utilizes vortex excitation vibrations. Preliminary experiments showed that it was expected to generate more than 10 times more power than the conventional planar-shaped wind power generation flag. In the present flag, the cylindrical Bluff Body, which excites vortices, also plays the role of a vibrating structure, and the wind speed region where these vibrations are excited is greatly affected by the boundary conditions corresponded to the different supporting methods. However, the authors have previously reported on the relationship between vibration and wind speed during power generation with the cylindrical shell which was assumed to be freely supported. In this study, the relationship between the wind speed range, the excited vibration mode, and the amount of power generated by the different boundary conditions are investigated experimentally. It was implied from the experimental results that superior supporting condition of the present cylindrical shell energy harvester for wind power generation characteristics will depend on the radius of the cylinder. Further study will be needed to establish the design method of the proposed wind energy harvesting method.

Recent advances in the development of ultra-low power electric devices have drawn attention to the study of wind power generation flags based on piezoelectric elements. However, the piezoelectric film wind power generation method has been a challenge to improve power generation density and durability. Therefore, a new piezoelectric cylindrical shell wind power generation flag had been proposed by the authors as a flexible and durable power generation structure that utilizes vortex excitation vibrations. Preliminary experiments showed that it was expected to generate more than 10 times power than the conventional planar-shaped wind power generation flag. It is also shown through theoretical considerations that in order to construct a cylindrical generator flag using piezoelectric film that increased power generation in the low wind speed region, it was necessary to excite the vibration mode of circumferential wavenumber n=2 in order to utilize Kalman vortex excitation in this wind region. Moreover, in order to make the conventional structure, which generates power at high wind speeds, resonate at lower wind speeds, the radius of the cylinder must be large when the thickness was fixed and the thickness must be thin when the radius was fixed. However, the effect of variation of size on power generation characteristics has not been verified experimentally. In this report, wind energy harvesting experiments were performed with a number of flexible cylindrical shell type piezoelectric harvester flags, which has different dimensions and also thickness/radius ratios, and the structural design method to construct superior energy harvesting shell type generator, which will be able to generate large power at low wind speed, was discussed.

It has been well known that bone has piezoelectric properties and these properties have been considered to be caused by the shift of the center of symmetry of the positive and negative electrical charge due to the strain of the collagen fibers included in the bone. Thus, it has long been considered that there were no piezoelectric effects in the hexagonal hydroxyapatite(HAp) which has center of symmetry of crystal. However, in recent years, the piezoelectric property of artificially synthesized HAp was reported. In the authors' previous report, a new result which showed the piezoelectricity of the hydroxyapatite(HAp) films fabricated by the pulsed laser deposition(PLD) method was reported. In this study, the effect of poling treatment on piezoelectric constant of pulsed laser deposited HAp films was investigated.

Piezoelectric film is a flexible, thin and lightweight sensor/actuator material. Conventionally, it has been used for the development of the thin and lightweight sound insulation control device based on the vibration control of plate or beam with piezoelectric film actuators and sensors. In most studies which has treated the relationship between the placement of piezoelectric films and control effects, metal materials (such as aluminum) of thickness ranging from 1mm to 5mm was considered as the controlled plate structures. However, there were few studies which treated the vibration analysis of much more thin plate materials with high flexibility such as resin materials of thickness under lmm. In general, vibration control effects of the flexible plate strongly depend on the placement of piezoelectric films. Especially, these dependencies tend to appear in case of fixed supported plate. Instead, depending on the placement of the piezoelectric film actuators, in the worst case, unwanted vibration modes of the plate are excited by these piezoelectric film actuators and the transmission noise will be augmented. In this study, at first, analytical models of rectangular plates with piezoelectric films are defined, and fundamental equations are derived. Then, the optimum placement of piezoelectric film actuators are investigated by forced vibration analysis of the plate. Here, since the application to sound insulation control is considered, frequency responses of the plate are evaluated in terms of volume velocity. After that, the behavior of the system is investigated analytically for the thinner plate with piezoelectric films in the optimum placements, and the results are discussed toward the development of the thinner and lighter sound insulation devices.

In recent years, wind energy harvesting systems using piezoelectric materials have been studied by a lot of researchers. However, energy harvesting methods using flexible thin piezoelectric films had not been well developed due to the extremely small power generation. In this study, a piezoelectric wind energy harvesting method using high-polymer films was investigated experimentally. At first, the feasibility of the systems was shown in laboratory experiment by using various shapes, sizes, and boundary conditions of piezoelectric films subjected to the artificial wind airflow from consumer air blower. Then, a flag-type piezoelectric wind energy harvester was manufactured and the characteristic against natural winds was verified by outdoor experiments. © 2013 SPIE.

In order to overcome the difficulties of multimodal active vibration damping of the flexible thin structure using simultaneous piezoelectric sensing and actuation, an noncollocated vibration control method, in which piezoelectric film sensors and actuators were shaped using different shaping functions, was proposed in this paper. At first, fundamental equations were summarized and vibration responses of the beam were derived based on the modal coordinate systems. Then, it was shown that by considering phase characteristics of the controller in conjunctions with the polarity of the piezofims in high order frequencies, multimodal control will be implemented both theoretically and experimentally.

Using direct and inverse piezoelectric effects of high-polymer piezoelectric films simultaneously, flexible structures are expected to be realized which possess vibration damping ability and are able to behave actively and autonomously such as biological systems. However, conventional studies have been limited to either developing high order controller in conjunction with sensor/actuator of basic shaping or developing sensor/actuator of complicated shaping function in conjunction with simple controller. In this paper, a new shaping design method of distributed piezoelectric film sensor/actuator for vibration control of flexible beams is proposed. At first, fundamental equations are derived, and a new shaping method in which the shaping function is described by the superposition of the modal strain functions is proposed. In the proposed method, the weighting coefficient is determined by a reciprocal of the cube of wavenumber. It is proved that in the case of simply supported beam, one example of the proposed shaping function is reduced to the conventional triangular shaping function. Numerical examples of designed shaping function for a simply supported beam and a cantilever beam are shown for single mode, multi mode and all mode sensor/actuator. © 2009 SPIE.

Using dirct and inverse piezoelectric effects of distributed piezoelectric films simultaneously, active flexible structures which posess vibration damping ability can be able to construct. However, conventional studies are limited to the control of relatively small (micron-order) displacements of thin flexible structures as well as numerical studies by handling controller design of software aspects. In this paper, several fundamental active vibration control principles, which will be valid in actual implementation, of smart flexible structures using piezoelectric films as distributed sensor/actuator have been developed. By applying each of these methods, it was verified that the enough vibration control effects were actually obtained and the theory agrees well with the experiment.

本論文では, 鉄道車輪/レール系騒音のうちレールから放射される転動音の低減手法として, 移動する車上に設置したデバイスによるアクティブ騒音制御法を提案し, その可能性についての検討を行った。まず, 車体の下部開放部からの放射音を下流側全域で静音化することが原理的に可能な手法として, 波動吸収原理に基づく制御コンセプトを提案し, 境界要素法による音響シミュレーションによりコンセプトの妥当性を示した。また, デバイスユニットのプロトタイプ1基を設計・作製し, 実験室レベルでの騒音制御実験を実施した。実験は, 騒音源としてスピーカからのランダムノイズとレールのランダム加振音の両方を用いて行い, 実際に騒音制御効果が得られることを確認し, 開発したデバイスの有効性を実証した。

A self-sensing actuator constructed by four laminated piezoelectric films is developed toward the smart vibration control of two-dimensional structures. First, three kinds of mechanisms of self-sensing acutuators with two or four laminated piezoelectric films are proposed by examining the combinations of film construction and bridge circuits of analog electric controllers. And those self-sensing actuators are applied to the free vibration control of the first mode of a cantilever beam and it is ascertained that the vibration suppression effects are obtained by all the three mechanisms and the theories show good agreements with the experiments. Finally, the mechanism constructed by four laminated piezoelectric films is applied to the vibration control of a simply-supported rectangular plate as an example of two-dimensional structures and it is verified that the vibration control effect is actually obtained and the theory agrees well with the experiment.

This paper presents the numerical analysis method of the nonstationary response of acoustical-structural coupling systems. The acoustical analysis is formulated by the Boundary Element Method based on the hyper-singular boundary integral equation in order to deal with very thin elastic structures in the open space. The structural analysis is formulated by the Finite Element Method using the triangular thin plate element. Those fundamental equations are coupled by using the force equilibrium and the flux continuity conditions in the Laplace transformed domain, and the time history of nonstationary responses are obtained by the numerical inverse Laplace transform. The validity of the proposed method is examined in comparison with an analytical result and besides by conducting the experiments of nonstationary excitation of thin plates installed in the rectangular acoustic tube which is excited by a sinusoidal sound pressure from the planewave-driving type speaker. Finally, a few numerical calculation examples are shown. Those analyses treat the flexible I-shaped and L-shaped acoustic tubes which are excited by the sinusoidal pressure generated at the one end of acoustic tubes, and air medium displacements and sound pressures traveling in the tube and transmitted to the out of tubes are visually shown.

It was investigated experimentally whether the sound decreasing effects of sound absorbing material structures on the sinusoidally vibrating rigid surface are obtained or not. In the experiment, the one-dimensional acoustic tube was used and its one end is excited by the sound absorbing material structure and the other end is closed by glass wool. The experiments showed that almost 70% sound pressure decreasing effect is obtained at the maximum in the frequency range of 1〜3 kHz for the hard porous or fiber aluminum sound absorbing materials with the back air space made by using honeycomb structures. And it is observed that the frequency dependency of this decreasing effects is qualitatively and almost quantitatively coincident with the square root of reflectivity of the stationary absorbing material structure. But, for the urethane foam, this tendency could not be observed. It is supposed to be the flexible vibrational characteristics of urethane foam.

As an example of passive vibration control devices, the dynamic vibration absorber installed in the main system of no-damping is considered and the vibration suppression effects for free vibration responses and forced steady-state and nonstationary responses are systematically examined as to the cases in which the device is designed according to the four typical design criteria, i.e., the conventional frequency shaped response function method (FPT), the linear quadratic optimal control theory (LQC), the minimum variance criterion (MVC) and the eigenvalue optimization criterion (EOC). As a result, the device designed by FPT, LQC and MVC shows almost equivalent vibration suppression effects and has a fairly good robustness, whereas EOC shows the worst effects of all except the settling time of free vibration. As another result, the frequency response evaluation method widely used as the criteria, for example, of transmission loss of noise insulating wall, transmission coefficient of silencer or H_∞ control theory turned out to be not necessarily valid especially for the nonstationary excitations.

Cross-sectional configurations of rail for reduction of rolling noise of high-speed railway; Shinkansen are examined. First, depending on the Timoshenko's beam theory, the random vibration of an infinite rail with various cross sections subjected to the surface roughness excitation is analyzed considering the coupling with one material particle which is the model of wheel traveling on it. Then, the distributions of sound pressures radiated from those vibrating rails on the slab track are calculated based on the Boundary Element Method. In order to evaluate the reduction effects of rolling noise, the line spectrum approximation is introduced, and the radiated sound powers are estimated for seven definite frequencies in the range from 500 Hz to 200 Hz and relative reduction effects in comparison with the standard 60 kg long rail of the present Shinkansen are examined, and the effective rail cross-sectional configurations for reduction of rolling noise are proposed from the viewpoint of acoustic engineering.

A self-sensing actuator using piezoelectric two films with different thickness and area, which are closely installed on one surface of general curved structures and are treated as two capacitors in the active RC bridge circuit, is proposed from the view-point of simplification of hardware aspects of devices toward the realization of smart structures. It is first implied that this device is effective in the following points, i.e., 1) compensation of ME noises, 2) ability of obtaining high gain feedback and enough control power and 3) compensation of temprature for pyroelectric effect. Then, vibration control effects are estimated by theoretical analyses of free vibration response and harmonic steady -state response of a cantilever which is an example of fundamental flexible structures, and the guideline for constructing control circuit is shown. Finally, the validity of proposed self-sensing actuator scheme is verified by conducting the experiment of free vibration response of a cantilever.

In the authors' 1st report, a smart and simplified self-sensing actuator technique using piezoelectric films with different thickness is proposed. In this paper, application of the proposed method to the vibration control of curved structures is investigated. A flexible circular ring is treated as an example of curved structures and piezoelectric films with different thickness are bonded on one surface of the ring. The two films are treated as two capacitors in the active RC bridge circuit, and these are totally used as a self-sensing actuator. At first, fundamental equations of the circular ring with proposed self-sensing actuator are derived and vibration control effects are estimated by numerical analysis. Then, vibration control experiment is performed using an aluminum circular ring, and it is shown that the lowest vibration mode is efficiently controlled.

Evaluation method of vibrational characteristics of laminated FRP shells including damping is examined. Natural frequencies and loss factors of FRP circular cylindrical shells subjected to three kinds of prestresses are obtained on the ground of the first-order shear deformation shell theory by applying the modified Galerkin method. The results show that natural frequencies generally decrease, whereas loss factors increase for such the prestresses as external pressure, axial compression stress and torsional shear stress. Besides, it turned out through parametric studies that it is fairly difficult to find appropriate constructions of anisotropic laminated layers for which the both of natural frequency and loss factor become concurrently large. Considering the above, the following criterion optimizing vibrational characteristics of such structures as shells with the fairly large damping and the high frequency distribution density is proposed, i.e., that the least value of the product of frequency and loss factor for all vibrational modes should be maximized from the viewpoint of optimizing the free vibration reduction characteristics, in stead of the criterion to maximize the fundamental frequency which is one of the conventional concepts.

Numerical analysis method of transient forced vibration responses of thick rotating shells of revolution is developed. The method can consider the anisotropic laminated layers and the effects of prestresses such as the in-plane compression stress, internal pressure and torsional shear stress. Finite element method is applied using truncated conical shell element based on the first-order shear deformation theory, and the finite strain is considered to execute the non-linear analysis of the quasi-static displacements due to the rotation and prestresses except for the case of internal pressure. Transient responses of a laminated truncated conical shell and a partial spherical shell subjected to concentrated step and half-wave sinusoidal shock forces are calculated and compared with the previous results based on the classical shell theory. Finally, the effects of three kinds of prestresses are systematically examined by using a truncated conical shell model with the both ends clamped.

The vibrational behavior of continuous systems such as beams, plates and circular cylindrical shells subjected to random parametric excitations is examined mainly from the viewpoint of possibility of unstable phenomena. The vibrational responses of those continuous systems are analyzed by means of simulation method using random sample functions of trigonometric series generated by random numbers. It turned out that unstable phenomena occur even for the cases in which random parametric excitation inputs have the fairly wide-band power spectra whose dominant frequencies deviate from, for example, the twice of the natural frequencies of continuous sytems. Besides, for such continuous systems as plates or shells which have the high frequency distribution density, unstable vibrations are generated concurrently in multi-vibrational modes. Finally, the experiment was carried out for a simply-supported beam subjected to the narrow-band random parametric excitation and it was ascertained that unstable vibrations really occur, and further the unstable figure domain made by the simulation analysis showed fairly good agreement with the experimental results.

Buckling analysis of a rotating circular cylindrical shell subjected to the prestresses such as external pressure, axial compression stress and torsional shear stress is carried out through the frequency analysis. The finite element method using the truncated conical shell element based on the first-order shear deformation theory is applied, and the finite strain is taken into consideration to obtain the quasi-static displacements due to the rotation and prestresses, except for the case of external pressure. Numerical results show that for three kinds of prestresses, the buckling loads become larger as the rotational speed increases, and it turned out that it is sufficient to estimate the buckling loads for the case of no-rotation from the viewpoint of safety reliability. Besides, it was shown that for the case of torsional shear prestress, the linear analysis of quasi-static displacement leads to the physically incorrect result, i.e., the circumferential displacement diverges at some rotational speed and becomes the reverse to the torsional direction at the higher rotational speed. Thus, it should be noted that the authors' previously reported result that is derived through the linear analysis based on the quasi-analytical method using modified Galerkin method must be corrected.

Analysis method of radiated sound from arbitray configuration solids shoked by an impulse is investigated mainly from the viewpoint of practical applicability. The analyses of vibrational response of solids and radiated sound from them are based on the Finite Element Method and the Boundary Element Method, respectively. And the both are formulated in the Laplace range and they are linked in such the meaning that the boundary conditions for BEM are directly given in this range by the Laplace transformed results of vibrational response of solids. The results of time domain of radiated sound and vibrational response are obtained by the numerical inverse Laplace transform using fast Fourier transform. As some examples of fundamental structure elements, straight and L-shaped beams, a circular plate and a ring are considered, and the theoretical results are compared with those of the experiments using the impulse hammer. It shows good agreement and it is proved that the proposed method is valid for practical use.

For the vibration suppression of flexible continuous systems, an I-shaped impact damper with parallel linear spring and dashpot is first proposed. And, as laboratory models, a beam and a L-shaped panel to which teflon and multiple impactors are installed are considered, and the equation of motion of those systems are formulated by the finite element method. Concerning the free vibration and the forced vibrations by harmonic and random excitations for those models, the results of numerical simulation and those of experiments are compared, and it shows the validity of theoretical modeling and the usefulness of the proposed I-shaped impact damper. Finally, on the ground of the theoretical analysis for the case of random excitation by band-limited white-noise, the basic examination of the multi-modes vibration suppression effects by multiple impact dampers is carried out.

Vibration control of a flexible beam with piezoelectric film sonsors/actuators is investigated. Triangular-shaped piezoelectric films are bonded on the both surfaces of a flexible beam, and are treated as collocated sensor/actuator pairs. Equations of motions of the beam and sensor output are derived for two boundary conditions: 1) fixed-free, 2) both ends simply supported. Direct velocity feedback (DVFB) control law is employed, and closed-loop stability is analytically checked using Lyapunov's direct method. Forced vibration responses of the beams are calucutated under the condition that the system is harmonically excited. Analytical results show that first several bending modes can be controlled with reasonable feedback gains. In the simply supported case, anti-symmet-rical modes (even modes) are also efficiently controlled, and thus it is shown that the proposed control scheme is valid for multi-mode vibration control' of flexible beams.

Vibration control experiments of a simply supported beam using piezoelectric film (PVDF) sensor / actuator are carried out to verify that the triangular-shaped film pair is effective for multi modes vibration control in comparison with the rectangular-shaped film pair. In the experiment, analog circuits are used to implement DVFB (Direct velocity feedback) control law. Frequency responses of displacemet of a beam subjected to a concentrated harmonic force are measured with sensor outputs and feedback voltages, and those show good agreement with the theoretical results. As predicted theoretically, it is shown in the present experiments that all of the first three vibrational modes are efficiently controlled by the triangular-shaped film sensor / actuator, wheres the rectangular-shaped film sensor / actuator has no control effect against the anti-symmetrical vibrational modes, i. e., the second mode.

Sound radiation characteristics of vertically vibrating rail are investigated to clarify the nature of rolling noise of high-speed railway, since the contribution of wheel movements to rolling noise is verified to be very small. The slab track is considered and steady-state vibration responses of an infinite-length rail excited by a concentrated harmonic force is first obtained for various frequencies on the ground of the Bernolli-Euler beam theory and by applying the Fourier transform. Then, by using the Boundary Element Method based on the Helmholtz equation, the generated sound pressure is calculated under the boundary conditions of rail surface movements and rigid ground, and the sound radiation characteristics are examined especially from the view-point of directivity. Besides, the influence of restoring and damping effects of the foundation of rail on the sound pressure level is studied. Finally, the theoretical results of sound pressure distribution are compared with the existing experimental results, and it shows fairly good agreement.

Multimodal vibration control of a cantilever beam using bonded piezoelectric film sensors and actuators is studied both theoretically and experimentally. Equations of motion of the Bernoulli-Euler beam with collocated bonded piezoelectric sensors / actuators are derived. Then, direct velocity feedback control is employed as the vibration control law, and applying Lyapunov's direct method, it is shown that this control law is stable for arbitrary vibration mode. Transient responses of the beam, with control and without control, are studied for the cases in which an impact force is applied to the tip of the beam. Numerical results and experimental results show good agreement, which shows the validity of the proposed control scheme. It is also shown that first three bending modes are efficiently controlled, and that in order to achieve more broadband vibration control, it is necessary to consider the dynamics such as extensional vibrations of the beam which is not considered in the present study.

This paper describes an analysis technique based on the boundary element method (BEM) for problems concerning transient sounds by impacted bodies of arbitrary shape that are in close proximity of a rigid infinite plane. The BEM is formulated using a new half-space Green's function which exactly satisfies the Laplace transformed Helmholtz equation and the rigid boundary condition on the infinite plane. The analysis is first carried out in the Laplace transformed domain using the boundary input values obtained by a numerical Laplace transform. Then, the results in the time domain are obtained by a numerical inverse Laplace transform. For a transient sound radiated by impacted bodies, transient acoustic radiation from a sphere and a cube impacted by a sphere are considered. The validity of the analytical results is examined by comparing it with the experimental results.

The analysis of problems concerning transient sounds radiated by impacted bodies using the boundary element method (BEM) is investigated, and a general-purpose analysis program which is valid for any type of sound source is developed. The Laplace transformation of the Helmholtz equation is employed in the formulation of the BEM. The analysis is first carried out in the Laplace domain by using the boundary input values obtained by a numerical Laplace transform. Then, results in the time domain are obtained by a numerical inverse Laplace transform. As an example of transient sound radiated by impacted bodies, the transient acoustic radiation emanating from a column and a cube impacted by a sphere are considered. The validity of these analytical results for time-dependent sound radiation is examined through comparison with the experimental results.

The analysis technique for problems concerning transient sounds radiated by impacted bodies is investigated by the boundary element method (BEM), and a general-purpose analysis program, which is available for any sound sources, is developed. The Laplace transformation of the Helmholtz equation is employed in the formulation of BEM. The analysis is first carried out in the Laplace transformed domain by using the boundary input values obtained by numerical Laplace transform. Then, the results in the time domain are obtained by numerical inverse Laplace transform. As a transient sound radiated by impacted bodies, transient acoustic radiation from a column and a cube impacted by a sphere are considered. The validity of these analytical results for time-dependent sound radiation is examined by comparing with the experimental results.

デジタルマネキンを用いたユニバーサルデザイン・CAD演習におけるプロジェクト型演習について紹介した．

デジタルマネキンを用いたユニバーサルデザイン・CAD演習の取り組みを紹介した

デジタルマネキンを用いたユニバーサルデザイン集合教育の取り組みを紹介した．

人間工学科におけるデジタルマネキンを用いたユニバーサルデザイン集合教育の取り組みを紹介した．

Piezoelectric film has two effects of direct piezoelectric effect and inverse piezoelectric effect. These effects can be used for the vibration control of flexible structures. In the authors' previous reports, a self-sensing actuator with laminated piezoelectric films was proposed and the vibration control effects against first and second mode of a beam and first mode of a rectangular plate were shown. However, vibration control effect against multimode of two-dimensional structure was not shown yet. Therefore, in this paper, a self-sensing actuator using laminated triangular piezoelectric films was proposed and its analytical model was derived. Then the validity of the proposed method was shown by comparing the results of an experiment of applying voltage to a triangular piezoelectric film actuator bonded on the plate, with that of theoretical analysis. Finally, multimodal vibration control of simply-supported plate was studied by numerical analysis.

Concerning the on-vehicle-type ANC devices based on the wave absorption principle for wheel / rail system, new concept of device construction was proposed to prevent the howling and to realize downsizing , i.e., the secondary sound actuator is to be separated from the detecting microphone of primary noise by the distances of 1/2, 3/8 and 1/4 times of wave length of dominant frequency (800Hz) of rolling noise. The validity of new idea was first ascertained by means of BEM simulation analysis and then the experiments using three kinds of devices were actually executed, showing the improved ANC effects for the fairly high primary noise level almost comparable to the practical level

In order to elucidate the characteristics of rolling noise of wheel / rail system which is to be the main cause of the conventional railway noises, first the coupling vibration analyses were carried out by using an infinite length rail model with tread surface roughness and FEM model of wheel, and then based on BEM with the boundary conditions of obtained vibration responses , the acoustic radiation powers and the distribution of SPL of sound fields on both of the slab and ballast tracks were calculated for the wheels with straight , TGV-type and corrugated web. Examining the influences of wheel configurations to the rolling noise, the methods of countermeasures to reduce that noise were implied.

著者らは既報において,複数の圧電フィルムを積層してブリッジ回路に組み込み,セルフセンシングアクチュエータを構成する手法を提案し,フィルムの形状,極性,配向角といったパラメータを変えたメカニズムについて,自由振動の制御実験を行った結果,はり及び平板について1次振動モードの制御効果が得られることを報告した.本実験では,実際には回路に組み込むアクティブおよびダミーフィルムの面積,厚さといったパラメータを完全に一致させることは困難であり,これによりブリッジのバランスは容易に崩れ,制御性能が大幅に劣化するため,回路内の可変抵抗を微調整する必要があった.しかし,この作業は試行錯誤で行わなければならない部分もあり,非常に煩雑であった.一方, ColeらはLMSアルゴリズムにより圧電素子の静電容量を同定する方法を提案し, Vippermanらはこの方法を応用して, DSPとアナログ乗算器を用いてブリッジ回路を構成し,圧電素子と参照コンデンサの静電容量の差を実時間で適応的に補償するシステムを構築,さらに圧電セラミックスを用いて片持ばりの自由振動の制御実験を行い,この手法の有効性を示した.以上を背景として,本研究では,煩雑な調整作業を回避するため,過去に提案した圧電フィルム積層型セルフセンシングアクチュエータに,LMSアルゴリズムによる回路の調整機能を付与して,積層圧電フィルムからなる自己調整機能を持つ分布型スマートダンパを開発することを目的とし,スマートダンパの自己調整機能及び振動制御性能を検証するために実験を行った.図A1(a)のように4枚の圧電フィルムを用いてアクティブ及びダミーフィルムを構成し,これらを制御対象である片持ばりに一体として積層,貼付して図A1(b)に示したDSPとアナログ乗算器を用いて構成されたブリッジ回路に組み込むことによって自己調整機能を持つ分布型スマートダンパを実現した.まず,自己調整機能を検証するため,制御ループを開いた非制御状態でブリッジ回路に微弱な白色雑音を入力し,自己調整機能を作動させた.ここで,アナログ乗算器の出力電圧v_の2乗平均値が最小となるように, DSPの出力電圧v_はLMSアルゴリズムに基づいて調整され,一定値に収束することを確認した.次に,振動制御性能を検証するため,自己調整機能を停止させ,収束したv_をアナログ乗算器に入力した状態で,はり先端に衝撃入力を与えて,励起された1次モードの自由振動制御を行った.この実験結果を図A2(a)に,また同図(b)には参考のためにv_を手動調整した場合の結果を示した.図中の破線は非制御時,実線は制御時のはり先端変位の時刻歴応答であり,両者はほぼ同等の制御効果が十分に得られていることが確認できる.これらの実験結果により,本研究では,アナログ乗算器とDSPを用いることで圧電フィルム積層型セルフセンシングアクチュエータを積層圧電フィルムからなる自己調整機能を持つ分布型スマートダンパを実現し,煩雑な可変抵抗の調整作業を回避できることを示した.

The possibility of a concept of active sound cancellation control based on the wave absorbing principle of conventional railway wheel/rail rolling and impact noises by on-vehicle-type devices was examined. First, theoretical simulations on the basis of BEM were executed, and then the experiments of active noise control were carried out by using multi-device-units installed on the panel system simulating the floor/side wall of railway cars, where both the simulated random rolling noise and impact noise measured in the real field were used. As a result, it was verified that the sound cancellation effects are actually observed over the relatively broad seeable space from the rail, showing the validity of the proposed concept.

An acive sound absorbing device unit of the transmission noise through a wall, using a plate planewave speaker as the secondary sound source, was developed toward effective suppression of aircraft interior noise. The controller was designed using reference accelerometer attached on the wall, and based on the Filtered-x LMS algorithm, its system identification was in advance performed so as to minimize sound level at one observation point, and then act as an off-line controller. At first, control effects were estimated by the numerical analyses using the system model identified from the actual experimental devices. Then, active sound absorbing experiments were performed with band limited white noise applied to the unit, and it was shown that enough control effects were obtained at plural observation points located in three dimensional space.

A wave absorbing control method using piezoelectric film sensor/actuator, namely quasi-waveabsorbing control which is based on relative displacement control, of a flexible thin-walled cantilever beam subjected to random displacement excitation is investigated. Vibration control experiment is performed with the triangular shaped sensor and the rectangular shaped actuator bonded on both surfaces of the beam, and velocity feedback control law which is expected to be most effective in the theoretical analysis is applied. Fixed boundary of the cantilever is subjected to limited bandwidth random noise excitation, and the relative displacement of the beam is measured. It is verified that good vibration control effects are obtained for the bandwidth containing three lowest vibration modes.

Concerning the rolling noise of wheel/rail coupling system, first the power spectrum of contact force between wheel and rail is calculated by random vibration analysis and besides the vibration responses of rail and wheel is obtained by use of Timoshenko beam theory for rail in addition to FEM model for wheel .Then, using those vibration responses as the boundary conditions of acoustic analysis of BEM, the acoustic powers radiated from wheel and rail are obtained and the rations of respective power to total power are estimated for three kinds of confgurations of wheel, that is, straight web wheel, corrugated web wheel with six circumferential wave number and TGV-type wheel.Concerning the rolling noise of wheel/rail coupling system, first the power spectrum of contact force between wheel and rail is calculated by random vibration analysis and besides the vibration responses of rail and wheel is obtained by use of Timoshenko beam theory for rail in addition to FEM model for wheel .Then, using those vibration responses as the boundary conditions of acoustic analysis of BEM, the acoustic powers radiated from wheel and rail are obtained and the rations of respective power to total power are estimated for three kinds of confgurations of wheel, that is, straight web wheel, corrugated web wheel with six circumferential wave number and TGV-type wheel.

Noticing the noise reduction effects of the drainage asphalt pavement, the method of estimation of radiation characteristics of automobile tire/road noises and the road design concept of reducing such noises are examined. By using FEM, the tire vibration responses depending on the grain size of road texture are obtained and regarding those responses and the normal acoustic impedance of the finite area simulating road surface as the boundary conditions for acoustic analysis by BEM, the sound pressures radiated from the tire on the both of the dense and porous asphalt pavements are calculated. As a result, it is verified that in the drainage asphalt pavement, the tire/road noise is more reduced than in the dense pavement by the suppression of horn effect in addition to the excess attenuation due to sound absorbing effect of porous asphalt.

The vibration analyses in which the head of the wheels is harmonically excited in radial direction were carried out by using FEM for the wheels of Straight web. TGV-type web and Wavy web with four kinds of circumferential wave number, and then by taking those vibration responses as boundary conditions the acoustic analyses using BEM were conducted to obtain the acoustic radiation power. And by random vibration analyses considering the rail surface roughness, the mean square velocities of rail at the contact point between rail and wheel were calculated. From the above results, the sound radiation powers of various-type wheels were examined in order to clarify the influence of wheel configurations upon the rolling noise of the railway wheel / rail system and to get the fundamental knowledge towards the optimal design of the configurations of the wheels with wavy web.

The concept of the active sound cancellation control of the railway wheel/rail noises by the On-vehicle-type devices is presented. And the apparatus of randomly exciting 60kg rail by the electromagnetic shaker which is enclosed with the panel system simulating the floor/side wall of the railway car was constructed. Further, one unit of the devices which realizes in principle the sound cancellation control of the see-through space was manufactured and the parabola-microphone and actuating speaker was installed on it in addition to the controller consisting of the analog electrical band-pass filter circuit group. And it was verified that the sound cancellation control effects are observed actually for the both cases of a speaker and the randomly excited rail system which were regarded as the primary sound sources.

The active sound absorbing device unit of the transmission noise through a thin plate using a plate plane-wave speaker as the secondary sound source was developed and its lightening and compacting construction methods of elements was examined by trying the various combinations of elements. The controller is designed on the basis of the Filtered-x LMS adaptive algorithm by using DSP under the condition that the thin plate is subjected to the band-limited white noise. It was verified by the actual control experiments that the improvement from the view-point-of lightening of the unit is attained as a whole by the passive insulation effect of the speaker elements in addition to the active sound absorbing effect in comparison with the case in which a plane-wave speaker consisting of the piezoelectric film was used.

The design methods of the optimum tuning and damping of the dual dynamic vibration absorber (D-DVA) for large-scale structures with very low frequencies were presented, arid the optimal construction layout which minimizes the undesirable moment applied to the base was examined. And then, for the both cases of displacement and force excitations, the approximate expressions for design parameters were proposed. Further, it was indicated that in the case of installing the D VA to the continuum structures subjected to the displacement excitation, the introduction of the new concept of the equivalent inertia mass in addition to the conventional equivalent mass and stiffness at the point of installation becomes necessary. Finally, by applying the present dual DVA to the vibration suppression of the first and the second vibration modes of a large-scale framework structure, the simulation results were obtained, showing the effectiveness of the present dual dynamic vibration absorber.

Vibration control of a flexible beam using piezoelectric film sensors and multilayered actuators is investigated. At first, the method of multilayered piezoelectric actuator is proposed for the purpose of improvement in vibration control effect against relatively thick structure. In the proposed technique, multilayered piezoelectric films are connected in parallel electrically and are driven simultaneously by the control voltage. Then, multilayered actuator is actually applied to a cantilever beam and by measuring the amplitude of semi-static displacement at the tip of the beam, it is shown that the actuator force generated by the proposed miltilayered actuator improves for the same magnification as the number of films. Finally, proposed method is applied with the piezlelectric film sensor to the transient vibration control of the cantilever beam and it is verified that the vibration control effect actually improves and the theory agrees well with the experiment.

Sound decreasing effects of sound absorbing material structures installed on the moving rigid surface were verified experimentally for both the stationary and the nonstationary cases by using the one-dimensional acoustic tube. The decreasing effects were evaluated in the frequency spectrum domain by taking the discrete Fourier Transform for the nonstationary case, and almost 70% sound pressure decreasing effect was observed at the maximum in the range of 0.5〜3kHz for the hard porous or fiber alminum sound absorbing material structures with back air space. Then two kinds of quantitative estimation methods of those decreasing effects were examined.

The concept of the active sound absorption method using thin and membranous piezoelectric film speaker is proposed toward the suppression of aircraft interior noise, especially large turbo-fun jet plane. At first, an active sound absorber unit is constructed with a secondary piezoelectric film speaker and an reference accelerometer, and the controller is designed using Filtered-x LMS adaptive filtering. Then, the active sound absorber unit is applied to the suppression of the transmitted sound through a thin plate, and by observing the sound attenuation at plural points, it is ascertained that the proposed method can actively absorb the transmitted sound, which has the property similar to the aircraft interior noise. Finally, a way of construction of the control system with proposed active sound absorber unit is presented for aircraft interior noise reduction.

Sound decreasing effects of sound absorbing material structures installed on the moving rigid surface were verified experimentally for both the stationary and the nonstationary cases by using the one-dimensional acoustic tube. The decreasing effects were evaluated in the frequency spectrum domain by taking the discrete Fourier Transform for the nonstationary case and almost 70% sound pressure decreasing effect was observed at the maximum in the range of 0.5 ∿ 3kHz for the hard porous or fiber alminum sound absorbing material structures with back air space. Then two kinds of quantitative estimation methods of those decreasing effects were examined.

The concept of the active sound absorption method using thin and membranous piezoelectric film speaker is proposed toward the suppression of aircraft interior noise, especially large turbo-fun jet plane. At first, an active sound absorber unit is constructed with a secondary piezoelectric film speaker and an reference accelerometer, and the controller is designed using Filtered-x LMS adaptive filtering. Then, the active sound absorber unit is applied to the suppression of the transmitted sound through a thin plate, and by observing the sound attenuation at plural points, it is ascertained that the proposed method can actively absorb the transmitted sound, which has the property similar to the aircraft interior noise. Finally, a way of construction of the control system with proposed active sound absorber unit is presented for aircraft interior noise reduction.

Characteristics of the impact sound at the joint of rail in the urban railway are investigated. The rail is modeled by a free-free Euler-Bernoulli beam on the Winkler foundation with springs and dashpots and the acceleration in the Laplace transform domain is calculated when a wheel impacts the one end of the rail vertically. Then the Laplace transformed radiation sounds are calculated on the basis of the Boundary Element Method by considering the flux which is expressed by the product of the above acceleration of rail and the air density as the boundary conditions. In the BEM, the rail surface is discretized by using the triangular linear element. And the time histories of radiated sounds from the rail are obtained by conducting the numerical inverse Laplace transform. On the ground of those results, the characteristics of radiated impact sounds from the joint of the rail are examined in addition to the generation mechanism of those sounds.

In the authors' previous report, a self-sensing actuator using laminated piezoelectric films with differnt thickness and area was proposed, and the validity of the proposed method against the lowest vibration mode was shown by performing vibration control experiments of a cantilever beam and a simply-supported plate. In these experiments, however, only rectangular shaped films were used, and furthermore, vibration control effects against higher modes was not verified experimentally. In this report, the present method is applied to multimodal vibration control of simply supported beam by using piezlelectric two films of differnet shapes and orientations. Two types of self-sensing actuators are proposed and five conbinations of thickness, shape, and oriantations of the two piezoelectric films are considered and vibration control effects are compared theoretically. Finally, vibration control experiments are performed using laminated triangular-shaped piezoelectric two films with different skew angle, and it is shown that vibration control effect was obtained against first and second modes of the beam.

Equation of motion of the dynamic vibration absorber for large-scale low frequency structures proposed previously is derived for the case with dual auxiliary systems and the numerical method of design of the quasi-optimal tuning and damping conditions of the dual case is presented. And it is verified by the simulation that the vibration suppression effects are improved in comparison with the single case. Then, applying to the three-degree-of freedom system with the fundamental frequency of 0.1 Hz, the superiority of the present method to the conventional design concept is shown in the low frequency range. Finally, the prototype of the present dual dynamic vibration absorber was manufactured to apply to the one-degree-of-freedom system with the natural frequency of 0.69hz and the vibration suppression effects were actually ascertained through the experiments of the free vibration and frequency response.

A model of automobile rotating tyre is constructed by the Finite Element Method using the truncated conical shell element based on the first-order shear deformation theory. And in order to investigate basically the characteristics of tread pattern excitation sounds, the influences of tread pattern pitch number and pattern arrangement on the vibrations of tyre surface are examined by approximating the pattern exciting mechanism by the sinusoidal contact pressure loading from the earth. As a result, it turns out that the vibration amplitude of tyre decreases as the number of pattern pitch increases and besides the pattern becomes stagger-type for almost all automobile running speeds. And as to the distribution of tyre surface vibration amplitudes for the circumferential direction, the vibration amplitudes become remarkably large at the parts of the trailing and leading edges.

A precise modeling of a rolling automobile smooth tyre is carried out and through the analyses of its vibrational behaviors the mechanism of the noise generation is considered. The analysis is formulated by the Finite Element Method using a truncated conical shell element and includes the effects of the inner pressure, rotation, laminated anisotropic layer structure and damping matrix re-constructed from the modal damping ratios. Not only the linear but also the non-linear vibration analysis is executed by considering the effect of large deformation. The linear vibration response to the contact load with the smooth earth becomes the standing wave forms on the stationary co-ordinate, whereas the non-linear vibration response shows some amount of harmonic vibration components of tyre surface, and it results in the fact that the noises possibly generate even from a smooth tyre.

It was investigated experimentally whether the sound decreasing effects of sound absorbing material structures on the sinusoidally vibrating rigid surface are obtained or not. In the experiment, the one-dimensional acoustic tube was used and its one end is excited by the sound absorbing material structure and the other end is closed by glass wool. The experiments showed that almost 70% sound pressure decreasing effect is obtained at the maximum in the frequency range of 1〜3kHz for the hard porous or fiber aluminum sound absorbing materials with the back air space made by using honeycomb structures. And it is observed that the frequency dependency of this decreasing effects is qualitatively and almost quantitatively coincident with the root of reflectivity of the stationary absorbing material structure. But, for the urethane foam, this tendency could not be observed. It is supposed to be the flexible vibrational characteristics of urethane foam.

A wave absorbing control method, namely quasi-wave-absorbing control, of a harmonically excited cantilever beam using piezoelectric film sensor/actuator is investigated. At first, based on the relative coordinate system, fundamental equations are formulated using wave propagation characteristics of the beam. And then, five control laws so as not to generate the reflected waves at the tip of the beam are derived with the shapes of both piezoelectric sensor and actuator taken into consideration. Theoretical analyses of steady state responses show that based on the proposed method, almost equivalent vibration control effects can be obtained in comparison with those obtained by the conventional wave absorbing control method based on the absolute coordinate. Finally, vibration control experiment is performed with the triangular shaped sensor and the rectangular shaped actuator bonded on both surfaces of the beam, and velocity feedback control law which is expected to be most effective in the theoretical analysis is applied and it is verified that good vibration control effects are obtained for three lowest vibration modes.

A self-sensing actuator constructed by four laminated piezoelectric films is developed toward the smart vibration control of two-dimensional structures. First, three kinds of mechanisms of self-sensing acutuators with two or four piezoelectric films laminated are proposed by examining the combinations of film construction and bridge circuits of analog electric controllers. And those self-sensing actuators are applied to the free vibration control of the first mode of a cantilever beam and it is ascertained that the vibration suppression effects are obtained by all the three mechanisms and the theories show good agreements with the experiments. Finally, the one mechanism constructed by four laminated piezoelectric films is applied to the vibration control of a simply-supported rectangular plate as an example of two-dimennsional structutures and it is verified that the vibration control effect is actually obtained and the theory agrees well with the the experiment.

A new-type of the dynamic vibration absorber for large-scale structures with very low frequencies is proposed. It utilizes the rotational moment of inertia of bar-type mass instead of the conventional concept of utilizing the inertia force of the mass of the auxiliary vibrational system. The optimal tuning and damping conditions of the proposed dynamic vibration absorber are derived by the Fixed Point Theory. Then, this design concept is applied to the first mode with frequency O.lHz of the three-degree-of-freedom system, and the superiority of the proposed vibration absorber in low frequency range is verified. Finally, a prototype of the proposed device was manufactured and the experiments of the free vibration and the frequency response were conducted, and the validity of the theory was ascertained.

This paper proposes the numerical analysis method of the nonstationary response of acoustical-structural coupling systems. The acoustical analysis is formulated by the Boundary Element Method based on the hyper-singular boundary integral equation. The structural analysis is formulated by the Finite Element Method using the triangular thin plate element. Those fundamental equations are coupled by using the force equilibrium and the flux continuity conditions in the Laplace transformed domain, and the time history of nonstationary responses is obtained by the numerical inverse Laplace transform. The validity of the proposed method is examined in comparison with an analytical result and besides by conducting the experiments of nonstationary excitation of thin plates installed in the rectangular acoustic tube which is excited by a sinusoidal sound pressure from the planewave-driving type speaker. Finally, a few numerical calculation examples are shown. Those analyses deal with the flexible straight and L-shaped acoustic tubes which are exited by the sinusoidal pressure generated at the one end of acoustic tubes.

In this paper, active vibration control of flexible structure by high-polymer piezoelectric films, which aims for the realization of smart structures, is investigated. At first, active vibration control method using piezoelectric films as sensor and actuator is discussed and the concept of distributed vibration control method is introduced. Then, several examples which are the author's studies are shown. The topics included are vibration control experiments of cantilever beams using rectangular-shaped sensor/actuator pairs, vibration control experiments of simply supported beams using a triangular sensor/actuator pair, wave absorbing control of cantilever beams using two pairs of triangular sensor/actuator, and vibration control experiments of cantilever beams and circular rings by a self-sensing actuator using piezoelectric films of different thickness. Finally, an overview of this study toward the future is presented.

As an example of passive vibration control devices, the dynamic vibration absorber installed in the main system of no-damping is considered and the vibration suppression effects for free vibration responses and forced steady-state and nonstationary responses are systematically examined as to the cases in which the device is desighned according to the four typical design criteria, i.e., the conventional frequency shaped response function method (FPT), the linear quadratic optimal control theory (LQC), the minimum variance criterion (MVC) and the eigenvalue optimization criterion (EOC). As a result, the device designed by FPT, LQC and MVC shows almost equivalent vibration suppression effects and has a fairly good robustness, whereas EOC shows the worst effects of all except the settling time of free vibration. As another result, the frequency response evaluation method widely used as the criteria, for example, of transmission loss of noise insulating wall transmission coefficient of silencer or H^∞ control theory turned out to be not necessarily valid especially for the nonstationary excitations.

An I-shaped impact damper for large-scale flexible structures was manufactured by way of trial using the machine elements of coil springs and magnet dampers. By installing it in the one degree-of-freedom system with the natural frequency less than 1Hz, the vibration suppression effects were ascertained for the steady-state harmonic responses. Secondly, on the ground of the numerical simulation, the vibration suppression effects and the appropriate placement method of multiple I-shaped impact dampers were examined by applying those to a large plane framework structure and studying the reduction of the first two resonance peaks, and it showed the effectiveness of the proposed I-shaped impact damper for large-scale flexible structures.

In the authors' previous report, a smart and simplified self-sensing actuator technique using piezoelectric films with different thickness and area was proposed, in which two rectangular shaped piezoelectric films are bonded on one surface of the structure and treated as two capacitors in the active RC bridge circuit. The validity of the proposed method was shown by performing vibration control experiments of a cantilever beam and a circular ring. In this report, the present method is applied to multimodal vibration control of simply supported beam as fundamental flexible structure. At first, fundamental equations of the system based on the proposed method are derived using energy principle and vibration control effects are estimated by numerical analysis to show effective shapes of the two films for multi-mode vibration control of simply supported beam.

This paper deals with active vibration control of flexible structure by high-polymer piezoelectric films, which is based on the concept of smart structure. At first, characteristics and problems of active vibration control method using piezoelectric materials as sensor and actuator are discussed. Then, the concept of distributed vibration control method is introduced and several examples from the author's studies are shown. Included in the topics are vibration control experiments of cantilever beams using rectangular-shaped sensor/actuator pairs, vibration control experiments of simply supported beams using triangular sensor/actuator pair, wave absorbing control of cantilever beams using two pairs of triangular sensor/actuator, vibration control experiments of cantilever beams and circular rings by a self-sensing actuator using piezoelectric films of different thickness. Finally, an overview of this study toward the future is presented.

本研究では、薄肉構造物の境界からの反射波を吸収する波動吸収制御法を圧電フィルムの利用によって実現することを目的とした。制御対象モデルとして、柔軟回転アームなどにも適用可能な片持ばりをとりあげ、適切に形状を設計された圧電フィルムセンサとアクチュエータがその表面に貼付されて一体化されたスマート片持ばりを作製し、理論解析および実験によって複数の振動モードに跨る広い周波数範囲にわたって制御効果が期待できることを示した。また、実験では１次モードを中心とする低周波数ほど理論解析結果に相当する効果が得られ、回転アームに適用した場合には、回転に伴う慣性力の影響が本圧電素子系では対応困難であることを確認した。

本研究では,圧電フィルムを用いた薄膜状ダンパ,すなわち任意の曲率を有する薄肉構造物の表面にシール状に貼付して外部の駆動回路に接続すれば,構造物の境界条件やフィルムのサイズ・貼付位置にかかわらず何らかの振動抑制効果を発揮するような,いわば「スマートダンパ」の開発を目的とし,その具現化の方法として,積層化した圧電フィルムの表裏にマトリックス状の電極パターンを形成させ,個々のユニットを外部の回路で分散制御的に駆動させる方法を提案し,スマートダンパとしてのメカニズムの設計手法について検討して,その有効性を数値解析および実験によって検証することを方針とした.平成17年度は,平成16年度のまで理論解析結果および予備実験結果を基礎として実際に薄膜状ダンパによる柔軟ばりのアクティブ制振を試みることを目的とした.まず,前年度の結果をもとに,スマートダンパの柔軟ばりへの適用を考え,4層構造の積層型圧電フィルムを作製した.ここでフィルム2層ずつをそれぞれ1枚のセンサ/アクチュエータとして用いる電磁シールド構造とした.次に,厚さ0.5mm,幅30mm,長さ215mmのアルミニウムの片持ばりの一表面に上記で製作した積層圧電フィルムを貼付し,このはりの一点に衝撃入力が加わる場合の減衰自由振動制御実験を行い,実際に制御効果が得られることを確認した.また,本手法におけるスマート化を達成するため,当該スマートダンパのセルフセンシングアクチュエータとしての自己調整機能についても検討し,ディジタル回路を援用したLMSアルゴリズムによってその機能が実現できることを確認した.以上の成果により,積層化圧電フィルムおよび外部の駆動回路によって,構造物の境界条件やフィルムのサイズ・貼付位置にかかわらず何らかの振動抑制効果を発揮するような,いわば「スマートダンパ」が実現できる可能性を確認できたといえる.

研究計画に対応させて、得られた成果を項目別に記述する。 1.「転動音と継目衝撃音の放射音特性の理論的・実験的把握」 境界要素法によるレールからの放射音の指向性の理論解析を行った。また、継目衝撃音については、東急目黒線の奥沢-大岡山間で実車両の衝撃音特性を測定し、インパルス性の低周波音よりもクラスターとしての高周波音変動を消音制御すれば良い、との知見を得、ほぼ800Hz付近に卓越周波数を持つ転動音を消音制御出来れば継目衝撃音も人間の耳障りにならない事が分かった。 2.「車両床・側板模擬パネル系およびレール加振装置の設計・製作」 60kgレールの踏面を動電型加振器で750〜850Hzのランダム波で加振する装置を設計・製作し、さらにこれを囲む車両床・側板を模擬したアルミハニカム板よりなるΓ形のパネル構造系を作製した。 3.「車両設置型デバイスの設計・製作と実際の消音制御実験の実施」 研究支援者である、ビーバ株式会社の八百板晃氏に委嘱して、波動吸収制御法の原理に則ったデバイスのプロトタイプの型5基を作製し、この1基に実際にパラボラマイクロホンとスピーカを実装した。 さらにアナログ電気回路系をベースとする広帯域フィルター群からなるコントローラを製作した。 以上のコントローラを1次騒音源としてスピーカを使用して調整し、実際に消音制御実験を実施した。 この結果、騒音源をスピーカに設定した場合には、レールから見通せる空間でほぼ-8〜-9[dB(A)]の騒音低減効果が得られ、また音源が実際のレールの場合でも-3〜-6[dB(A)]の消音制御効果が得られる事を確認する事が出来た。

本研究では,昨年度に引き続き,複数の圧電フイルムを積層構造とし,これと外部のブリッジ回路との組合せによるセルフセンシングアクチュエータについて検討した.前年度の結果をもとに,積層型セルフセンシングアクチュエータの二次元構造物への適用を考え,4層構造の積層型セルフセンシングアクチュエータが2次元平面上での振動検出/制御が可能となるように,積層パラメータを設計した.制御対象構造物として,厚さ0.5mm,幅240mm長さ300mmアルミニウムの平板を考え,その一表面に上記で設計した積層化圧電フイルムを貼付した場合について,理論解析によって,得られる振動制御効果について検討した.平板の境界条件を周辺単純支持条件として,その1点に衝撃入力が加わる場合の平板の観測点変位の時刻暦応答を非制御時・制御時について計算した結果,変位応答について支配的であった1次振動モード(固有振動数36.0Hz)について制御効果が得られることを確認した.さらに実際に平板に圧電フイルムを積層化して貼付し,ブリッジ回路をパワーOPアンプに基づくアナログ回路で構成した実験装置を作製し,これを用いて制御実験を行った結果,実際に制御効果が得られ,また理論解析と実験が良く一致することも確認できた.以上より本手法によって二次元構造物のスマート振動制御が可能であることが理論的・実験的に示された.

本研究では,昨年度に引き続き圧電フィルムを分布型センサ/アクチュエータとして用いた柔軟梁の振動制御についておもに数値解析的に検討した.振動モードのひずみ関数の重畳によってセンサ/アクチュエータの形状を決定する手法を適用して,まず,梁の境界条件を両端単純支持とした場合について考え,モード形状関数が三角関数で表現できることを考慮して,センサ/アクチュエータ形状を重みつきのフーリエ級数展開で表現し,重畳に考慮するモード次数を1から徐々に増加させていった場合について具体的に計算した.各項につける重みを1/(波数)^3とした結果,従来のモードセンサ/アクチュエータに相当する項数1の場合から,数個の振動モードを検出/操作する多モードセンサ/アクチュエータ,さらに広い周波数帯域にわたって存在する非常に多くの振動モードを検出/操作するセンサ/アクチュエータ形状が求まり,この極限が従来用いてきた三角形状センサ/アクチュエータに収束することも確認できた.また,この重みは絶対値が等しく符号が逆となる二種類の重みが各モードに対して設定できるので,原理的には無限個のセンサ/アクチュエータ形状があることもわかり,奇数次項の符号を正/負にとることにより大きく分けて二つの形状が存在することを示した.ついで,この1/(波数)^3の重みをつけたセンサ/アクチュエータを同時使用し,直接速度フィードバックを適用した場合を考えて,各モードのモード減衰効果の制御による増分について定式化し,この重みによって,各モードに均一に減衰効果が付与されることを示した.よって,これを基準として重み値を増減させてセンサ/アクチュエータ形状を設計すれば,二個以上の任意の個数の振動モードからなる振動モード群に対し減衰効果の付与を任意に設定することが可能となる.最後に,モード形状関数が三角関数で表現できない境界条件への適用例として,片持ばりに対するセンサ/アクチュエータ形状を計算した.全モードを検出/操作したい場合,長方形状あるいは三角形状ではなく本手法の適用によって求まった新たな形状を用いることが適していると考えられる.

まず強い異方性積層構造を持つ自動車タイヤが接地しながら転動するときの強制振動応答を解析するために、回転するタイヤのモデリングについて検討した。その結果、一次せん断変形殻理論に基づくせっ頭円錐殻要素を用いた有限要素法により、一般軸対称殻であるタイヤを変肉厚のせっ頭円錐殻要素の集合として近似することとした。以上の方針に基づき、まず内圧,トルク,面内圧縮力のような初期荷重が作用し、回転する一般軸対称殻の過渡的強制振動応答を解析するための数値解析法を開発し、実際に回転する部分球殻,せっ頭円錐殻に衝撃荷重が作用する場合の過渡的強制振動応答を解析し、古典理論(薄肉殻理論)による場合と比較することにより開発した手法の妥当性を検討した。 次の段階として、上述のモデルに減衰の影響を取り込み、定常的強制振動応答の数値解析法の開発を行った。すなわち、実際にデータとして与えられるのは非回転時のタイヤのモード減衰比であることから、固有ベクトルを用いて減衰マトリックス[C]を逆構成し、さらにこの[C]にジャイロ項を加えてM-C-K基礎方程式系を導出し、高次モードを省略するためにこの方程式系を状態空間表示し、右固有ベクトルと左固有ベクトルを用いてモード解析し、高次モードをtruncateして定常的強制振動応答を解析する数値解析手法を開発した。さらにこれを回転円筒殻の場合に適用してプログラムの妥当性の検証を行った。 今後は、上記手法を実際の転動タイヤに適用してその定常的強制振動応答を解析し、その振動応答値を境界条件として境界要素法による音響放射音圧を解析する数値計算法のプログラムを作成して計算を行い、解析結果に基づいて自動車タイヤの騒音発生メカニズムの解明を行う予定である。