Search

A new method on optimum design of control system of small degrees of freedom (DOF) is proposed for a structure of large DOF in order to assure stability against disturbance which includes high mode vibration. The original structure is modeled by the finite element method (FEM). A modal model of p DOF is made with this FEM model, in which p is the number of the modes whose stability have to be assured. A small model of n DOF (n < p) is made by system identification with the frequency response function. A feedback control system is composed with the n DOF model. The optimum values of the weighting coefficients of the performance index in the optimum regulator theory are determined by sensitivity analysis under the condition that the n DOF control system is stable against the vibration of p natural modes in order to prevent spillover phenomenon without adopting any additional means. Vibration of a steel plate till llOOHz in which nine natural modes are included can be suppressed with a control system of only two DOF in an experiment with using the proposed method.

An approach is proposed for simultaneous optimum design of a structure and feedback control system by sensitivity analysis for the following two purposes. One is to decrease both the response and the control force of the system under a white noise disturbance force. The other is to modify the gain, the pole and the zero-point to the desirable values. The weighting constant of the feedback control system, and mass, stiffness, shape, dimension, etc. of the structure are adopted simultaneously as the design variables. The proposed method is verified by a model simulation.

This study is to establish new evaluation scales of sound quality which is more suitable for the human sense of hearing than the conventional evaluation scales such as A‐weighted sound‐pressure level. The authors focus on fan noise and have investigated the meaning space of its sound quality by hearing tests and factor analyses. The hearing tests were performed using semantic differential (SD) method and their test results were analyzed to extract dominant factors of the fan noise sound quality. The factor analyses, influence of noise level and 1/3 octave band level on sound quality of fan noise were also investigated. It was found that the sound quality of fan noise had two major factors; ‘‘offensive’’ and ‘‘booming‐powerful’’ factors. The evaluation of hearing test using a paired comparison method was performed in order to investigate the correlation of these two factors with physical quantities that represent noise level and quality such as A‐weighted sound pressure level and loudness level. Analysis of hearing tests results revealed that ‘‘offensive’’ factor has positive correlation with the physical quantities such as A‐weighted sound pressure, but ‘‘booming’’ factor has negative correlation with them.

Noise and vibration problems in automobiles are caused by plural vibration sources and complex transfer paths. In general, diminishing the noise and vibration level is a matter of great importance for a lightweight and low‐cost design. In this paper, the noise and vibration problem caused by pavement roughness in automobiles, that is, the road noise problem, is discussed. By means of traction of a vehicle with constant speed, measurement of noise and vibration caused by only the factor of pavement roughness in automobiles is accomplished and the contribution of road noise in automobiles is investigated in detail using acoustic modal analysis and principal component analysis.

Some approaches to the simultaneous optimum design of multiple dynamic absorbers (DAs) are presented for suppressing multiple resonance peaks of a multiple‐degrees‐of‐freedom (MDOF) structure simultaneously, taking changes of natural modes and natural frequencies of the structure due to added mass effects of DAs into account in the design. First, some methods for determining an equivalent single‐degree‐of freedom (SDOF) system of the subject MDOF structure are explained, in order to make possible the application of the usual design method for the SDOF system by Den Hartog to the subject MDOF structure. Second, some guides in determining the best place on which DAs should be attached in the subject structure are indicated for giving the best play to DAs efficiencies. Third, three kinds of approaches to the simultaneous optimum design are proposed using the modal analysis. Validity and usefulness of the proposed approaches are demonstrated by both computer simultation and experiment using a plate and a simple structure.

It is not always possible to obtain characteristic matrices from modal parameters obtained by experimental modal analyses, such as curve fitting. If the degrees of freedom of the mathematical model are different from those of the structure identified, which occurs in almost all cases, contradiction occurs between the modal parameters when transformed to physical parameters. This paper proposes certain constraints that modal parameters must satisfy in order to be transformed to mass, stiffness and damping matrices without contradiction. A nonlinear optimization technique is used to solve these contraints. A new multireference curve fitting method in the frequency domain is also proposed. The number of unknown parameter depend only on the number of degrees of freedom identified, regardless of the number of response points. This method is effective when there are a number of response points. some experimental models are examined to validate this method.

In determination of the model parameters of a mechanical structure, many kinds of curve fit techniques have been developed, using the theory of experimental model analysis. In the present paper, six methods of multi station multi degree of freedom curve fit techniques, by which multiple eigen values of multiple transfer functions are identified, are compared with one another. First, the model parameters of a mass spring system of five degrees of freedom are determined by the above six methods. Thereby, the input data of the transfer functions are disturbed by adding white noise to them. Thus, the toughness of the above six methods against the noise is checked and compared individually. Next, as an example of the application of these six methods to a complex structure, the model parameters of a white body of an actual automobile are determined by these methods, using the transfer functions measured by the vibration test as the input data. The accuracy and the calculating time of these six methods are compared with each other.

Division d'une structure en premiers elements divises, eux-memes divises en seconds elements divises, et ainsi de suite jusqu'aux n-iemes elements divises. Analyse du mode naturel de chaque (n−1)―eme element divise avec les modes naturels des n-iemes par la technique CMS (Component Mode Synthesis), et ainsi de suite jusqu'a l'analyse finale de la vibration de la structure totale. A titre d'exemple numerique, analyse d'une plaque et comparaison avec les resultats experimentaux et ceux de la methode par element fini

The authors propose a method for calculating accurately the residual compliance matrix of structures with free-free boundary condition in this paper. A total structure must be divided into several substructures when it is analyzed by substructure synthesis methods. In doing this, the majority of the substructure will be under free-free boundary condition. For such substructure the residual compliance matrix cannot be obtained accurately by the usual method. So it is important to propose a new method for calculating the accurate residual compliance matrix of the structures with free-free boundary condition. Algorithms of the usual method and the method proposed by the authors as well as Hansteen are given. Numerical examples about a simple case are also shown.

塩化ビニール・モノマーの暴露が関係していると思われる門脈圧亢進症の1例について報告する. 症例は38歳の男性で,18年9カ月間にわたり塩化ビニール製造作業に従事していたが,脾腫,食道および胃の静脈瘤を伴う門脈圧亢進症と診断され脾摘出術および食道離断術を受けた.術前の検査では血小板数の減少,ICGおよびBSPによる色素排泄能の障害が認められたが,GOT,GPT,およびアルカリフォスファターゼ値は正常であった.肝の組織学的検査では門脈域の線維化が著しく,小葉間におよぶ線維性の隔壁があり,類洞内皮細胞の僅かな増加がみられた.摘出脾では著明な慢性うっ血像を示し,脾洞の増生,髄索および血管周囲の線維化がみられた.患者は術後8カ月目に絞拒性腸閉塞で同部の切除術を受けたが,術後に腎不全および汎発性腹膜炎で死亡した.

This paper proposes a two-dimensional active mass damper which is controlled by a software servo system in order to reduce the vibration of tower structures caused by strong winds or earthquake. The purpose of the two-dimensional active mass damper is to control effectively the two-dimensional 1st vibration modes of the structure. In designing the software servo system, LQ control theory is applied. The results of experirental examination on the design show that although the 1st vibration modes are well controlled, a resonance peak at the 2nd mode increases as a resonance peak at the 1st mode is decreased and runs into spillover instability. It is also shown that the spillover instability can be prevented easily by a dynamic absorber attached at the maximum amplitude point on the 2nd vibration mode.

Impellers rotate at high speeds, and therefore in order to improve the efficiency of turbomachines it is necessary to take into account not only the static strength to withstand the centrifugal force but also the dynamic strength to withstand vibration in the design stage. In practice various kinds of exciting forces are applied to impellers, but in this investigation a screen with slots around its periphery is positioned in front of the impeller and the impeller is excited aerodynamically through this screen. The resonant vibratory stresses and the pressure distribution are measured simultaneously in resonant condition when the impeller is rotating at high speeds. The relationship between the resonant vibratory stresses and the pressure distribution is discussed in detail by analyzing the frequency variation of the two components.

To attain optimum design of vibration cotrollers to suppress many resonance peaks of machine structures, it is necessary to know the equivalent mass at the mounting location of the controller. This paper shows two ways for estimating the equivalent mass : one is the modal analysis method, and the other is called the mass responsive method, which utilizes the variation of the natural frequency of the structure when an additional mass is attached. The first method mentioned is useful to identify modal mass having "physical meaning", while the other method is most suitable for application in the experimental analysis. The accuracy of these methods are compared with each other by applying them to three kinds of mechanical structure.

Dynamic characteristics of stationary impellers can be analyzed accurately by the Cyclic Symmetry Method; however, it is necessary to calculate dynamic characteristics of rotating impellers. In this report, equations of motion and those of vibration for rotating impellers which are divided into finite elements by the F.E.M. are presented. In these equations, effects of centrifugal forces and Coriolis' forces on dynamic characteristic.s of rotating impellers are considered. In this report, it is made clear that critical speeds and critical modes can be found in connection with centrifugal forces and that computation of natural pairs considering Coriolis' influence resolves into eigenvalue problems of Hermitian matrices.

The previous report shows a quadrupedal walking robot which has a limitation on its walking speed because of walking static balanced with three legs by movement of the center of gravity. This paper proposes a new walking method, that is, semi-dynamical walking with two-legs-support, such as horses. For a realization of this kind of walking, it is necessary that each ankle of the legs has a control mechanism on the roll angle, because they support the position in walking. In this paper, the walking pattern is studied through analyzing. the dynamic stability in walking, and developed walking control programs on a software servo control system which is broken up in order to control the micro-processors. The experiment for a quadrupedal walking robot shows that this kind of walking is 4 times faster than the previous kind of walking.

A cylinder block of 4 cylinders is analyzed by the component mode synthesis method. The component mode synthesis method is a general method of analysis of the vibration of a complex mechanical structure using the natural modes of the components. A structure is divided into some components. All components are classified into master components and branch ones. The natural modes of each component are determined by the finite element method. The natural modes of all components are synthesized to form the generalized system coordinates. The equation of motion under these system coordintes is solved to know the vibration of the total structure.

Static and dynamic forces which have to be applied to input pairs of an arbitrary-type mechanism for many kinds of actions are analyzed numerically, in order to simulate motion of an articulated robot. Uicker's method of analysis, based on the matrix algebra for a link mechanism of a closed loop, is extended to mechanisms of an opened loop and a compound loop. The static forces necessary to compensate the forces acting from the outside are analyzed by the principle of virtual work. The static and the dynamic forces necessary to compensate the inertia force, the gravity force, the spring force, the spring force and the damping force are analyzed using Lagrange's equation of motion. The forces of two kinds of robot models are calculated numerically by the present method and the results are compared. Both results agree well with each other.

Vibrations of cylinder blocks of diesel engines with 4 and 6 bores are analyzed by the reduced impedance method proposed by the authors. A cylinder block is divided into some component structures, and the mechanical impedances of each component are calculated by the finite element method. These impedances are reduced and composed to get a unified equation of motion. This equation is solved to get the natural modes and the natural frequencies of the total structure. On the other hand, the natural frequencies are detected experimentally, using the Fourier translations of the measured impact waves of the force and the acceleration. The natural modes are observed by the holographic technique with an argon gas laser. The calculated results agree well with the experimental ones.

The vibration of a diesel generator package is analyzed by the substructure synthesis method. namely the building block approach. The diesel generator package is divided into three substructures, namely a generator, a common plate and a diesel engine. The transfer function of each substructure is measured by a vibration test under the free condition. The transfer functions of all substructures are combined to make an equation of motion for the total structure. This equation is solved, and natural modes. natural frequencies and dynamic responses are obtained. The connecting parts between three substructures which are composed of bolts and supporting metals are considered springs of one degree of freedom. The dynamic characteristics of rubber isolators placed between the common plate and the base are obtained experimentally, and are introduced into the analysis. The analyses are performed for both a model and an actual machine, and the results are compared with experimental ones.