It is well known that the vibration control problem for automobiles and railway vehicles with semi-active suspensions is classified as a control problem in a bilinear system. Bullet trains and railway vehicles have lighter body in order to improve acceleration; these vibrations in the body are easily induced by various disturbances due to rigid and elastic dynamics. Currently, passive dampers such as air suspensions and axle springs are installed on railway vehicle trucks as countermeasures for such vibrations. This study presents an effective controller, based on the H_∞ theory, for vibration suppression in railway vehicles and describes a method of synthesizing this robust controller by considering unstructured and structured uncertainties that are applicable to a bilinear system. The performance of the proposed controller and its robustness toward uncertainties are examined by numerical calculations that simulate a railway vehicle subjected to disturbances due to vertical uneven railway tracks, the variations in its mass due to boarding passengers, and the modeling errors caused by non-controlled modes. This enables a comparison of the proposed control method with the conventional one in terms of the robustness toward parameter variation. Thus, this result shows the high robustness and usefulness of the proposed controller.

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This paper deals with reducing floor impact vibration and sound by using a momentum exchange impact damper. The impact damper consists of a spring and a mass that is contact with the floor. When a falling object collides with the floor, the floor interacts with the damper mass, and the momentum of the falling object is transferred to the damper. In this works a computational model is formulated to simulate dynamic floor vibration induced by impact. The floor vibration is simulated for various sized damper masses. A proof-of-concept experimental apparatus was fabricated to represent a floor with an impact damper. This example system consists of an acrylic plate, a ball for falling object, and an impact damper. A comparison between simulated and experimental results were in good agreement in suggesting that the proposed impact damper is effective at reducing floor impact vibration and sound by 25% and 63%, respectively.

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In crawler-type construction machines, flexible suspension system like bogie mechanism type suspension is used to reduce and disperse the load acting on the running gear and to absorb the vibration from uneven ground. However, the quantitative effects of the bogie are not so clear. In this paper, by using a modeling and simulation method for crawler-type construction machine with bogie mechanism, which is developed by the authors, in traveling on firm grounds with continuous bumps, representative simulation cases to analyze the dynamic behavior were conducted. Then K-type and X-type bogie as flexible suspension and locked K-type and X-type bogie as rigid suspension were selected. In two bump pitch cases, effects of the bogie mechanism introduction and the bogie type on the dynamic behavior of the machine, such as the lower rollers load and the bouncing and pitching behavior were shown quantitatively and discussed.

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This paper deals with a two-degree-of-freedom forced system composed of a main system and an impact damper which has been analyzed by many researchers. Periodic solutions, bifurcations, chaos, and vibration quenching are discussed. A shooting method for impact systems presented by authors is used in numerical calculations. The following results were obtained: (1) Unsynmetric periodic solution with four collisions per period and subharmonic vibrations with many collisions were found. (2) Discontinuities in the stability of the periodic solutions caused by impact were shown using characteristic multipliers. (3) Two routes to chaos were found, namely, the period doubling route and the torus doubling route. (4) Hyper chaos was found for the first time in the impact damper system. (5) The vibration quenching problems for the narrow frequency region near the resonance point and for the wide frequency region were discussed.

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This paper describes a Wave Intensity Analysis (WIA) method based on experimental data, which is named Experimental WIA (EWIA). EWIA uses coupling and internal loss factors obtained experimentally through the power injection method, commonly applied in Experimental Statistical Energy Analysis (ESEA). The directional dependency of the energy is introduced by deriving a transmission coefficient for each boundary at each frequency band. Then, EWIA is applied to predict the vibration energy of simple plate systems and the results are compared to directly measured energies, WIA and ESEA energy predictions. The results show that EWIA can improve the WIA and ESEA predictions without any additional effort. Moreover, EWIA provides more information than ESEA about the characteristics of the energy field, which allows a more detailed analysis of the structure.

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A theoretical method is presented for calculating the absorption coefficient of a multi-leaf microperforated panel absorber. In this work, the possibility of using multi-leaf type of microperforated panels without solid backing panel is investigated. The number of panels varies from 2 to n (≥2). The sound absorption coefficient is calculated based on electro-acoustic analogy by taking the sound transmission coefficient due to the absence of solid backing panel into consideration. The optimum performance of leaf microperforated panel absorber is also investigated as the function with respect to the design parameters such as perforation ratio, diameter of holes and distance between panels. The numerical results show that the configuration of leaf of microperforated panels can increase absorption coefficient at low frequency region. This fact will give an advantage to the multi-leaf microperforated panel over conventional microperforated panel arrangements. That is, to solve the problem of quite narrow frequency band absorption effect, especially in mid-high frequency region corresponding to their resonant frequencies, that the conventional microperforated panel arrangements inherently possess. Experiment results are also presented that show a reasonable agreement with the theoretical results. Some feasible application ideas of the multi-leaf type of arrangement are also presented.

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A generalized transfer stiffness coefficient method using graph theory is developed in order to improve the applicability of the transfer stiffness coefficient method. In the new method, an analytical model is expressed by a weighted signal-flow graph, and the graph is contracted according to the series and parallel contraction rules. The computational complexity and the memory requirement for the contraction process are both minimized by choosing the optimal contraction route. In addition, it is possible to develop a data-driving program that is applicable to various structures without updating the source program. An algorithm based on the present method is formulated for the in-plane longitudinal and flexural coupled free and forced vibration analyses of a two-dimensional framework structure. Furthermore, an overview for applying the method to a three-dimensional framework structure is briefly presented. The validity of the present algorithm is confirmed by the results of numerical computations.

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Equilibrium states of a rotating circular membrane subjected to a transverse distributed load are investigated. In order to analyze large transverse deformations of an extremely thin membrane, rotationally symmetric deformations are assumed and the membrane theory of shells of revolution and the von Karman theory are applied to formulate basic equilibrium equations. Numerical integration method of the equilibrium equations are proposed taking account of buckling due to large transverse deformation and approximate displacements, stress and strain distributions in equilibrium states are obtained while the method cannot give buckling waves. The results based on the two theories are compared and it is found that the results are approximately the same even when the transverse deflection is extremely larger than the thickness and the applicable scope of the von Karman theory is estimated. An experiment is also conducted to measure transverse displacements of a rotating circular membrane under gravity in vacuum with a wide range of rotation speeds. It is shown that the displacements given by the analyses fit into the displacements measured by the experiment.

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The present paper is concerned with the free flexural vibration of an elliptical plate subjected to a uniform in-plane force in its middle plane. The edge of the plate treated here is rigidly supported against transverse displacement and restrained elastically against rotation. The rigorous expression of the vibration displacement is obtained in the form of a Mathieu function series in accordance with conventional thin-plate theory, neglecting the effects of shear deformation and rotary inertia. The frequency equation from which the eigenfrequencies can be obtained numerically is derived by applying the orthogonality of the Mathieu function. Numerical values of the lowest dimensionless eigenfrequencies are tabulated and graphed against various dimensionless rotational spring stiffnesses, dimensionless in-plane forces and aspect ratios.

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