In the previous report, we propose modeling focusing on "sigmoid function" as an attenuation model combining viscous damping and Coulomb friction characteristics, and conduct numerical simulation on higher-order spectra (HOS) analysis and higher-order frequency response analysis in that model was carried out. In order to further model various characteristics, we focused on "continuously differentiable friction model" proposed by Makkar et al. Then, a modified modeling was performed with respect to the model in consideration of asymmetric terms. Numerical simulation analysis on higher order spectra(HOS) such as bispectrum was performed in these attenuation models. Effectiveness of the proposed method is presented and examined. These are the main points of this research.

We investigate the transient response of a linear system subjected to non-Gaussian random excitation.The excitation considered in this study is prescribed by probability density function and power spectrum with bandwidth parameter. Two kinds of the probability density functions of the excitation are taken into consideration, i.e., bimodal distribution and Laplace distribution. First, a stochastic differential equation is constructed using the probability density function and the power spectrum, and the excitation is generated by solving it numerically. Then, using the generated excitation, the transient response distribution of the system is calculated by Monte Carlo simulation while changing the bandwidth parameter and probability density function of the excitation. Likewise, the transient response variance and kurtosis are also calculated. Based on these calculation results, we discuss the transient response characteristics from the viewpoint of the transient response distribution, variance and kurtosis. It is shown that dynamic behavior peculiar to the transient response which cannot be seen in the stationary response exists.

The probability density function of the stationary response of a single-degree-of-freedom nonlinear stiffness system under non-Gaussian random excitation is analyzed. The random excitation is modeled by a zero-mean stationary stochastic process prescribed by both the non-Gaussian probability density and the power spectrum with bandwidth parameter. In this paper, two approximate analytical methods for the probability density of the stationary displacement of the system are presented based on the knowledge of the characteristics of the response distribution observed in the previous study. One of the two methods is used when the bandwidth of the excitation power spectrum is narrower than that of the frequency response function of the system, and the other is used in the case of the wider bandwidth than the system bandwidth. By using these methods, the response distribution can readily be obtained without complicated calculation.In numerical examples, the proposed methods are applied to a nonlinear system under three types of nonGaussian random excitation whose non-Gaussianity is quite different from each other. The results demonstrate that for all excitation probability densities considered in this paper, the response distribution obtained through the present methods is in good agreement with Monte Carlo Simulation result in both cases where the excitation bandwidth is narrower and wider than the system bandwidth.

In recent years, research on random response analysis of a system including viscoelastic elements modeled by fractional derivative has begun to attract attention. The moment equation method is a typical method in the field of random response analysis of a system including integer-order derivative. In this study, the method to derive the moment equation corresponding to a linear system including fractional-order derivative of order 1/2 and to evaluate the statistics of the response is proposed. In addition, it is also shown that the value of the cross-correlation term between the input and the response in the moment equation can be evaluated by the fractional-order differentiation of the cross-correlation function between the input and the response. It is demonstrated that this method is effective for various non-white random excitation through analysis examples.

We propose a new equation used in an analytical method via complex fractional moments (CFM) for the response distribution of a system under combined Gaussian white noise and random pulses. CFM is related to a Mellin transform of a probability density function (PDF), and by obtaining the CFMs of all order along the imaginary axis, the original PDF can be recovered. The PDF of the response of the above-mentioned system are governed by the generalized Fokker-Planck (FP) equation. By applying a Mellin transform to the generalized FP equation, the governing equations for the CFMs of the response can be derived, and by solving these equations, the CFMs are obtained. By using an inverse Mellin transform for the response CFMs, we can get the PDF of the response. However, the accuracy of the PDF obtained by such a procedure is low near the origin. In order to overcome this problem, we introduce new equation which connects PDF and its CFMs and is based on the inverse Mellin transform. By using this equation, the error of the PDF near the origin could be drastically reduced for various nonlinear systems. The effectiveness of present method is demonstrated by comparing with the Monte Carlo simulation results.

This paper shows a fundamental study to apply the principle of metamaterial to solid waves. A method of making the effective mass negative and an effect of the negative mass for a lumped parameter system in which the governing equation is isomorphic to the central difference approximation formula of the wave equation are investigated from the viewpoint of damping / vibration isolation. The results are as follows: 1) The effective mass can be negative by connecting the dynamic damper or the Sky Hook spring to each mass of the main system. 2) The amplitude can be reduced with increasing distance from the vibration source by making the effective mass negative. 3) The interaction between them is very small when connecting normal structures to negative massed structures.

This paper proposes a new method on how to absorb the vibration energy of a single-degree-of-freedom structure by using an active mass damper operated by a position controller and neural oscillators with a multilayered structure. The proposed system having the single neural oscillator has not adapted successfully to parameter changes of the structure. On the other hand, recent studies in biology have demonstrated that multiple oscillators have hierarchical network structures to ensure adaptation to environmental changes. Thus, in order to improve the robust performance of the AMD system, the target value of the AMD mass is generated using a neural oscillator network synchronized with earthquake-induced acceleration responses of structure. As a result, the new proposed system can obtain higher vibration suppression performance than the conventional system. And numerical simulation showed that vibration control of the structure was performed appropriately even after changing parameters of the structure.

This article presents exact algebraic solutions to optimization problems of a double-mass dynamic vibration absorber (DVA) attached to a viscous damped primary system. The series-type double-mass DVA was optimized using three optimization criteria (the H_∞ optimization, H₂ optimization, and stability maximization criteria), and exact algebraic solutions were successfully obtained for all of them. It is extremely difficult to optimize DVAs when there is damping in the primary system. Even in the optimization of the simpler single-mass DVA, exact solutions have been obtained only for the H₂ optimization and stability maximization criteria. For H_∞ optimization, only numerical solutions and an approximate perturbation solution have been obtained. Regarding double-mass DVAs, an exact algebraic solution could not be obtained in this study in the case where a parallel-type DVA is attached to the damped primary system. For the series-type double mass DVA, which was the focus of the present study, an exact algebraic solution was obtained for the force excitation system, in which the disturbance force acts directly on the primary mass; however, an algebraic solution was not obtained for the displacement excitation system, in which the foundation of the system is subjected to a periodic displacement. Because all actual vibration systems involve damping, the results obtained in this study are expected to be useful in the design of actual DVAs. Furthermore, it is a great surprise that an exact algebraic solution exists even for such complex optimization problems of a linear vibration system.

This paper describes a cantilever-type dynamic vibration absorber whose natural frequency can be tuned by using piezoelectric negative stiffness. Because the property of the negative stiffness is determined by the capacitance of the negative capacitor which is coupled to the piezoelectric element, the natural frequency of the cantilever-type dynamic vibration absorber can be tuned by using a variable capacitor for the negative capacitor. In this research, we proposed a new tuning method for the natural frequency of the dynamic vibration absorber using the phase difference between the host structure and dynamic vibration absorber. The effectiveness of the proposed method was verified through simulations and experiments.

Dynamic vibration absorber (DVAs) are effective passive damping devices that are widely used. The typical structure consists of a mass, a spring and a dashpot that is attached to a structure in order to reduce the dynamic response of the structure. However, the tuning process of them is complex and expensive. Although the DVAs with some rotary elements can overcome the weakness, these investigations have not yet been completed. As large earthquakes often occur recent years, the improvement of the damping method is required. This paper presents the results of experimental and analytical studies of the performance of a dynamic vibration absorber with rotary elements in a horizontally vibrating system. This damper consists of some rotary elements, which rolls on the cylindrical surface of a primary mass. A frictional force is also added to the system to suppress the amplitude of the primary mass. The rotary elements and the cylindrical surface used in this study were SUS304 and PMMA, respectively. It is shown that the frictional force and the particle size influence the damping performance. The validity of this damping is examined by a comparison of the response of the primary mass between the experimental result and analytical result obtained using conventional tuned rotary-mass damper.

In the latest trend in engine technology, diesel engines and high-power engines, low cylinder engines are widely used. These engines contribute to strong torsional vibration within the powertrain systems. On the other hand, automatic transmission (AT) is required to use a lock-up clutch system which links engine and gear train directly from low engine rotation speed. Lock-up damper, torsion damper in torque converter is not sufficient to absorb the torsional vibration. Therefore, the centrifugal pendulum vibration absorber (CPVA) is developed to suppress the torsional vibration. The natural frequency of CPVA is proportional to the engine speed. Then it is expected to suppress torsional vibration in wide rotation range of the engine speed. However, the natural frequency of the CPVA varies due to the nonlinearity when the vibration amplitude of CPVA is large. In this study, the optimum path of the CPVA to suppress the torsional vibration is discussed.

Dynamic absorbers are widely used for suppressing the vibrations of beam-like structures such as skyscrapers. These dynamic absorbers utilize the shearing force that exerts on structures (hereinafter refer to them as shear-type dynamic absorbers). In the previous paper, the authors proposed a moment-type dynamic absorber utilizing the bending moment that exerts on a beam (it is designated as a moment-type dynamic absorber). The effects of vibration suppression of the moment-type dynamic absorber attached to a cantilever and a simply supported beam were discussed theoretically and experimentally. In this paper, the authors consider another type of dynamic absorber utilizing both of shearing force and bending moment that exert on a beam (it is designated as a shear-moment-type dynamic absorber). The frequency responses of a cantilever beam to which a shear-moment-type dynamic absorber are discussed theoretically and numerically. Trial shear-moment-type dynamic absorber was manufactured using a three-layered sandwich beam. The effects of vibration suppression of the dynamic absorber were measured using an electromagnetic vibration machine. The experimental results showed that the shear-moment-type dynamic absorber is more effective than the shear-type and moment-type dynamic absorbers for suppressing the vibration of the beams. The experimental results were compared with the calculated results.

Due to the frequent earthquakes, Japan has suffered tremendous damage, so studies on equipment to control building vibration have been actively conducted. One of them is using active mass damper (for short, AMD). This device comprises a movable mass, an actuator for driving the mass, an acceleration sensor and a computer. Based on the signal of the vibration obtained from the acceleration sensor, computer calculates the command value so that the AMD can reduce vibration. Feeding back the value, the mass is driven by the actuator, and damping is performed by the generated reaction force. AMD stroke is proportional to the amplitude of the vibration. Therefore, there is a problem that AMD stroke exceeds the range of AMD when it controls vibration of large amplitude. we propose AMD which does not need to consider the range of motion by utilizing centrifugal force. Unnecessary force components are canceled by rotating the two eccentric weights in mutually opposite directions, and a force component in only one direction can be obtained. Therefore, it can solve the problem of conventional AMD. In this paper, it shows the overall control system of proposed AMD. In the simulation performed using the proposed method, we can reduce building acceleration by 37.0 % in RMS.

In order to further augment the bullet train's travelling velocity, a profounder comprehension of the wheel axle hunting motion is indispensable. An analytical expression for the natural frequency was early derived for the so-called geometrical hunting, but such model was unable to describe the inherent damping effects. Recently, analytical expressions for the damped natural frequency and damping ratio were proposed for the so-called dynamical hunting, by imposing restrictions on the ratio between the lateral and vertical creep coefficients, and also, on the ratio of the track span to the yawing diameter. However, instead of finding a pair of complex conjugate roots, and two real roots for the characteristic equation, two pairs of complex conjugate roots were obtained. Thus, due to the faulty model, the damping effect induced by the contact of the wheels with the rails was somewhat inaccurately predicted. Purpose of this work is to achieve accurate expressions for the hunting natural frequencies and damping ratios, without imposing geometrical and/or tribological limitations into the model, and furthermore, to evaluate the stability of the wheel axle.

A viscoelastic material is sometimes applied to the damping element of a dynamic absorber. However, since the dynamic characteristics of a viscoelastic material are temperature dependent, it is considered that the vibration damping performance may deteriorate due to changes in the natural frequency and damping ratio. In general, adjustment of its natural frequency is a simple matter of changing the mass and spring stiffness, but adjustment of its damping ratio is more problematic. This paper focuses on the difficulty encountered in adjustment of the damping ratio, proposes a structure for a dynamic absorber capable of suppressing the change in damping ratio due to temperature dependence, and develops a design method. The dynamic absorber is a cantilever type which consists of two plate springs, and a viscoelastic material which is placed between these plate springs. By means of this structure, it is shown that the damping ratio has a gentle curve with respect to temperature characteristics. Moreover, the peak of the damping ratio can be set to the target value at the set temperature by adjusting the thickness ratio of the two plates. The validity of the theory was confirmed by a vibration test using a shaker.

This study is a basic research to propose a simple estimation method of the maximum response value using response reduction factor in seismic response analysis of multi-input piping system with friction characteristic. In the linear system, a method for estimating the maximum response of the multiple input system by adding the maximum response from each input has been proposed. In addition, in a condition of one input system having nonlinearity such as friction, it can not be applied to multi-input nonlinear system. Assuming actual piping, response analysis of multi-input nonlinear system is necessary for rationalization of seismic design. Therefore, in this study, we introduce a nonlinear strength as the frictional force and clarify by simulation what kind of influence it will have on the maximum response of piping system under various conditions. Furthermore, we compare the results obtained by simulation with those of experiments and examine whether the proposed estimation method can be actually used.

This study tries to evaluate the more realistic number of equivalent load cycles for extremely-low-cycle fatigue evaluation to earthquake inertial loads in the seismic design of mechanical components. A simple “energy equivalent” method, analogizing balance between the accumulated plastic deformation energy due to input earthquake wave and the total hysteretic energy loaded typically during strain-controlled cyclic load test, was proposed and applied. Several single degree of freedom vibration systems with bi-linear load-deflection function were analyzed for 48 strong earthquake motions observed in Japan. The calculated number of equivalent load cycles were found strongly dependent on the characteristics of wave forms and system parameters such as natural frequencies and elastic limit load, however it was realized that the numbers lie mostly below 20 to 30 cycles. These numbers, as the estimated equivalent load cycles, might be concluded enough for the extremely-low-cycle fatigue evaluation of mechanical components during earthquake. As future investigations, more systematic studies especially on the in-structure earthquake response and cyclic loads from relative displacement such as Anchor-Movement would be valuable and necessary.

In Great East Japan Earthquake in 2011, fall accidents of escalators occurred. In the fall accidents, the escalators connected the third floor and the second floor. These occurred in commercial facilities of steel frame buildings. In general, escalators are set on beams of buildings without fixation. The cause of the fall accidents was that the escalators came off from the beams of the buildings by the great earthquake more than expected. After the escalator accidents, the quake resistance standard was revised in Japan. According to this standard, the layer displacement of buildings to be expected during earthquake is more than before. However, it is considered that a non-fixed part of an escalator collides with a beam of a building by an earthquake. In addition, the collision may give compression and residual displacement to the escalator. Therefore, the purpose of this study is to grasp dynamic behavior of an escalator at earthquake which considers impact with the beam. In this paper, behavior of an escalator during earthquakes is compared by difference of restoring force characteristics of escalator and confirm the validity of bi-linear model. In addition, as a preliminary analysis for the vibration experiments, dynamic behavior of an escalators during large earthquake is investigated by seismic response analysis model which considers interaction with the building.

Four fall accidents of escalators utilized in three shopping centers occurred during Greatest East Japan Earthquake in 2011. Based on the fall accidents, the quake-resistance standard of the escalator was revised in Japan. In the new quake-resistance standard, inter-story deflection assumed during earthquakes was set larger than before. It is conceivable that an existing escalator receives compressive load from a building. Therefore, it is necessary to investigate how the escalator truss behaves due to compressive load. From the above background, this study builds a finite element analysis model of the escalator truss that is subjected to compressive load based on results of a compression experiment of the escalator trusses of actual machine size. The validity of the analysis model is investigate by comparing with the compressive experiment of the escalator truss of the actual size.

In order to investigate the behavior of rigid body by rocking vibration, free vibration experiment, excitation experiment by sine wave and numerical response analysis were conducted. As a result, free rocking vibration in which the period and amplitude of rocking vibration decrease due to temporal change, and the restitution coefficient decreases depend on amplitude. And, the overturning acceleration amplitude that a structure overturn, changes complicated depend on frequency. It was found that the repulsion coefficient greatly affects the rocking vibration at the nonstationary response.

Many earthquakes have occurred in Japan since long ago. Many damages have been reported in the medical field, and it was revealed that there is a problem with the fixing method of medical equipment. Much medical equipment has casters and lock them as earthquake countermeasure. However, in the case where casters are locked, equipment may vibrate greatly and fall over. On the other hand, in the case where casters are not locked, equipment may move greatly and collide with other equipment and people. In previous study, for the purpose of preventing significant movement and falling of medical equipment with casters, it was proposed controller adapted Instantaneous Optimal Control theory with ER brake for caster wagon that simulated medical equipment. However, in experiment, the controller was not able to reduce relative displacement response and absolute acceleration response sufficiently. In this paper, we describe the result on new controller adapted Sliding Mode Control theory. First, we designed sliding mode controller and switching hyperplane for it. Next, we verified reduction performance of the controller by simulation and experiment. As a result, we confirmed that new controller is able to reduce displacement response and absolute acceleration response for multiple seismic waves effectively.

According to the Fire and Disaster Management Agency's date, there was over 5,620,000 people who ever transported by ambulance during 2016. And with the influence of sudden brake or different road conditions, the vibration is directly converted to the patients in ambulance. It could worsen the situation of bodies by impacting on organs even worse make the breathe stop and hearts stop beating, which is called CPAOA. So our group is aiming at making the patients feel comfortable during driving by buffering the vibration and avoiding CPAOA. That's the purpose of why we designed this acceleration decrease device and we estimated the effect of reduction of acceleration by taking real road test.

The sick and wounded who is conveyed to a hospital is conveyed with a stretcher from the spot to an ambulance, and fixed on vibration proof frame which reduces driving vibration in an ambulance to hospital. There is possibility of the sickness and wound aggravation in them by driving vibration. However, in question to ambulance crew, some people answered that vibration proof frame is ineffective. The purpose of this study is an evaluation of the vibration reduction performance of vibration proof frame. We evaluate acceleration reduction performance by graph of acceleration and acceleration PSD, max acceleration, max acceleration decreasing rate, acceleration RMS, acceleration RMS decreasing rate. The first experiment is a vertical vibration experiment using the vibrating table. By the result of this experiment, max acceleration is decreased at the head and the chest, but it is amplified at the head. Acceleration RMS is amplified at the head, the chest, and the foot. The second experiment is a driving experiment on road in Fukui city area by using a car. By the result of this experiment. Vertical max acceleration is decreased at the head, but it is amplified at the foot. Vertical acceleration RMS is amplified at the head and the foot. Front/back max acceleration and acceleration RMS is amplified at the head and foot.

The tuned mass damper (TMD), which is often used as the vibration control device, is effective against wind shaking, but in order to reduce the earthquake response the mass of the TMD must be increased. On the other hand, in the case of a device (inertial mass damper) that rotates the weight at high speed by a ball screw mechanism and obtains a large inertial mass effect, since a large mass effect is obtained with a small device mass, it is effective for reducing the earthquake response. However, there are few researches on effective placement method and optimum design of inertial mass dampers for multi-mass systems. Therefore, the purpose of this research is to effectively reduce the vibration response of the structure by investigating effective placement method of the inertial mass damper in the low stories of the structure and adjusting the parameters. The object to be analyzed is a 10-story structure, and the inertial mass damper is incorporate in up to the second floor. Adjustment was made to the acceleration response magnification of the top floor for each examination case. As a result, the method of arranging the series and parallel incorporation in the first floor is the most effective in reducing the vibration response.

Japan belonging to the circum-Pacific orogeny has suffered tremendous damages from earthquakes. Vibration control for buildings has been developed to improve strength of structures and prevent damages from earthquakes. Active Mass Damper (AMD) has been used as a vibration control device for buildings. AMD generally consists of acceleration sensor, mass, actuator and controller and is installed at the top of the building. When vibration of a building is detected by an acceleration sensor, AMD generates force against the building's vibration and counteracts the vibration. However, the acceleration sensor has a disadvantage that it cannot accurately detect low frequency vibration. In the center of city skyscrapers are increasing, which have a low natural frequency. Therefore, using an acceleration sensor for vibration control of a skyscraper by AMD is a factor that degrades the performance of AMD. In this study, we propose to detect building's vibration by image processing technology in order to improve the performance of AMD. A camera is installed in the building and takes a picture of the landscape. When the building vibrates, the landscape in the image moves. The vibration of the building itself is calculated by the image processing technology using the movement. This method can accurately detect low frequency vibration while it is difficult to detect high frequency vibration since it acquires the displacement information of the building. In this paper, it shows the performance difference by detection of acceleration sensor and image processing technology. We conducted experiments in which buildings are reproduced by simulation and building's vibrations are detected by actual devices. We showed that the proposed method can further reduce the vibration by 11.9% than the acceleration sensor.

Subduction-zone earthquake and local earthquake has been happening for the past several years. A lot of industrial facilities were damaged by them. Seismic isolation structures are receiving a lot of attention these years. Most of seismic isolation structures only act on horizontal earthquake. But because semiconductor producing equipment such as electronic beam exposure equipment is supported by air suspension, it could response to the vertical earthquake easily. To protect those equipment from earthquake, the three-dimensional seismic isolator must be developed. The helical coil spring is one of the seismic structure and it is used for absorbing vibration and shock. General single coil spring has high rigidity in the vertical direction and low rigidity in the horizontal direction. Therefore, it is necessary to lower the rigidity in the vertical direction to achieve three-dimensional isolation using coil spring. In this paper, three-dimensional seismic isolator using multiple coil springs are devised. It is analyzed by the finite element method. Coil springs which is wound circle, triangle, square and pentagon are analyzed. The seismic isolation capability while coil springs in the seismic isolator are inclined has been verified. The paper clarified the winding shape of coils and the inclining angle of springs in the seismic isolator which could lower the three directions of stiffness by performing eigenvalue analysis and time history response analysis on seismic isolator model. As a result, circle is the best shape for coil spring to achieve lowest stiffness and seismic isolation effect. It could reduce the acceleration response to short-period earthquake.

After the Great East Japan Earthquake of 2011 and the Kumamoto Great Earthquake of 2016, it seems necessary to upgrade earthquake countermeasure technology for further infrastructure conservation. As one of these efforts, we began developing a high-performance three-dimensional seismic isolation system that can isolate vibration to a level that people can not feel. This paper describes the full-scale seismic excitation experiments on new three-dimensional seismic isolation device using a pneumatic cylinder and the negative stiffness linkage in parallel on the air flotation stage. As a result of the excitation experiment of the seismic waves of KiK - net Mashiki-Machi (the Kumamoto Earthquake), the acceleration of the seismic isolation system was reduced to 1/15 in the horizontal direction and 1/3 in the vertical direction.

The response of the vibration control system using swarm intelligence for pseudo random wave has been investigated. As an example of swarm intelligence, a swarm of ants can find an optimal route between their nest and the food in various environment using special pheromone. In this sense, the network of agents in a swarm may have some kind of intelligence or higher function appeared in a simple agent, which is defined as the swarm intelligence. The concept of swarm intelligence may be applied in diverse engineering fields such as flexible pattern recognition, adaptive control system, or intelligent monitoring system, because some kind of intelligence may emerge on the network without any special control system. In previous studies, the swarm intelligence was applied to a mechanical vibration control system composed of a network of units equipped sensors and actuators. Five units composed of a displacement sensor and a variable dynamic damper were placed on each mass of the five degree-of-freedom lumped mass system. A unit composed of a sensor was placed on the basement. Each unit was connected to each other to exchange information of state variables measured by sensors on each unit. Because the network of units configured as a mutual connected network, a kind of artificial intelligence, the network of units could memorize the several expected vibration-controlled patterns and could produce the signal to the actuators on the unit to reduce the vibration of target system. In this study, pseudo random wave response of a vibration control system was simulated. The results showed that the vibration control system could reduce the vibration, especially the response to first natural frequency compared with ON-OFF controller.

This paper discusses on non-contact vibration control of an elastic long shaft by using active magnetic bearing (AMB) system. An experimental system is built. An elastic shaft is supported by two ordinary bearings with an AMB is located in the middle of the shaft to suppress vibration computer simulation and control experiments are carried out. As a first trial simple Proportional-Derivative (PD) feedback controllers are applied and vibration suppression of the shaft is succeeded, as for rest shaft.

The connected control method (CCM) utilized reaction force between buildings as damping force by using connecting springs and dampers. Integrated connected control method (ICCM) to high-rise building split into four substructures is already presenting and its effectiveness is already confirming. Besides, Distributed CCM(DCCM) is also presented to connect buildings by using plural dampers on multiple layers in order to ease stress concentration. In this paper, to investigate the applicability of ICCM with DCCM to real buildings, experimental apparatus be modified and it is carried out precise examination, through computer simulation and experiments. As the results, the performance of ICCM with DCCM was clearly shown.

The structures with long periodic natural period such as high-rise building has been applied a response control device such as Tuned Mass Damper (TMD) with passive, semi-active and active type to reduce a wind induced vibration. The additional mass type damper is basically constructed from a moving mass, spring element for tuning natural period and damping element. In general, although there is a lot of type using a guide rail to support a dead load of mass, the static friction force is the most important design problem in a starting acceleration for long periodic TMD since the friction coefficient often becomes about 5/1000. For example, if the moving mass is designed to be 10 ton with 5/1000 friction coefficient, the inertia force has to be over 500 N to start the moving mass on a guide rail. Therefore, the starting acceleration of TMD depends on a friction coefficient of guide rail to support the movable mass. This study has been examined about a low friction type TMD with under 0.01m/s2 starting acceleration using an air floating system. The technique of floating system has applied to a flow dynamic conveyer to convey coal, gypsum, ash in iron places. Moreover, the floating system for a base-isolation has been already applied to some structures. Sakamoto and Sanpei et.al. developed the floating system for a detached house to lift up in seismic event over a setting acceleration. Moreover, Fujita et.al. investigated a base isolation system for light wait mechanical structure such as a server rack using an emergency earthquake prediction warning. This paper describes the system concept, the loading test to confirm a friction characteristic of proposed system as a basic performance and shaking table test to examine an actual performance of floating speed against some acceleration trigger as a first step of the research and development.

This paper describes natural frequency reduction of a seismic isolator table using the negative viscous damping and negative Coulomb friction. Noo et al. proposed the seismic isolator table using a DC motor and electrical circuit. The natural frequency and the damping ratio of the isolator can be tuned using the electrical circuit. In addition, the resonance is suppressed by the vibration absorber using an LRC circuit. The problem of the deflection and buckling of a spring was solved by this method; however, the natural frequency of the isolator could not be reduced sufficiently because a viscous damping and Coulomb friction were not negligible. Therefore, we proposed a new electrical circuit that cancels the viscous damping and Coulomb friction in this research. The effectiveness of the proposed method was verified through the simulations and experiments.

In recent years, steel-framed houses are increasing in Japan. Traffic vibration problems sometimes occur in steel frame houses, because of small damping force. TMD is generally effective in such the case. but it does not become popular because of the tuning cost. Therefore, in this research, we develop Auto tuning/ Advanced Tuned Mass Damper (ATMD) which can be tuned automatically. This device has the structure which apparent spring constant is changed by rotating the turntable to adjust the natural frequency. In the experiment, the accelerometer was vibrated sine wave on a small shaking-table. We investigated whether the vibration frequency matches the natural frequency of ATMD. There was a little error in calculation to convert frequency to angle, but good results were obtained.

Oil dampers have been widely used for vibration suppression of vehicles, buildings structures and other devices. Despite being used for a long time, it is indispensable to experiment to know exactly the damping performance of this oil damper. The reason is that the flow of hydraulic fluid in the cylinder is complicated and the magnitude of the pressure loss caused by the convective vortex generated around the piston cannot be accurately estimated by the computer. Many exiting design formals of the oil damper had considerable different from the experimental value because the influences of the convection vortex were ignored. On the previous report, the authors estimated exactly the influence of the convective vortex of an oil damper which has an annular clearance between the piston and cylinder as a flow passage of oil using a numerical analysis of the fluid, and had obtained the calculation results which were very close to the experimental values. On this report, this calculation method was applied to another types of oil damper, that is, a damper having a circular small hole in the piston and a damper having a bypass flow passage in the cylinder wall. Because it is not a good method to divide the fluid region in these dampers into the computational grids by a unified method, we have used the overset grid method.

Piping systems crossing between isolated and non-isolated structures are designed to have relatively long length not to restrict the displacement of the isolated structure during earthquakes. Therefore, the natural frequencies of these piping systems are not high enough to avoid the resonances due to earthquake movements. In such cases, supports are required not to restrain the displacement of isolation, and to suppress the resonances of the piping systems. Because of this requirement, rigid supports cannot be applied to crossover piping systems. In this paper, the method of seismic response reduction for crossover piping using inertial mass element is proposed. Inertial mass element generates the force which is proportional to the relative acceleration acting on the element. In this paper, it is shown that the participation factors of the target vibration modes are minimized by optimizing the parameter of the inertial mass element. Additionally, by earthquake response analysis, it is confirmed that the resonances of piping systems are suppressed without restraining the response displacement of the isolated structures.

This study proposes a dynamic characteristic of Linked Fluid Inertia Mass Damper (LFIMD) for deflection distribution control of three-story structures. The damper consists of three oil dampers linked. This damper making it possible to control the story deflection by moving linked three piston rods. First, we study the basic dynamic characteristics of the damper. The dynamic loading test shows that the damper exerts high linking stiffness and stable viscous damping. Secondly, we calculated dynamic characteristics of LFIMD by taking the characteristics of a damper (FIMD) obtained from experiment. Finally, analytical study shows that can control story deflection efficiently. Using this system, we are able to reduce installation radix of damper without decreasing link stiffness.

This paper proposes a novel tuned rolling granular damper. The damper consists of a cylindrical container partially filled with granular materials. The container, rotating on the cylindrical surface of the primary mass, is used as a tuned vibration absorber. The friction and the collision between the granular materials and the walls of the cavity results in an energy dissipation. The advantage of the damper is that it has simple structure and can operate in extreme temperature environments, where most conventional dampers would fail. This paper investigates the damping efficiency in a horizontally vibrating system under sinusoidal excitation. The granular particles used in this study are made of steel and are of uniform size. It is shown that the mass ratio and particle size influence the damping performance. The validity of this damping is examined by a comparison of the response of the primary mass between the experimental result and analytical result obtained using conventional tuned rotary-mass damper.

In this report, static restoring force of a post-buckled Titanium–Nickel-based shape memory alloy plate is experimentally investigated and dynamic property of a passive vibration isolator for vertical direction using post-buckled shape memory alloy is investigated. From the static restoring force measurement test, we newly detected that Ti-Ni-base shape memory alloy plate reveals a negative tangent stiffness in a certain deflection range in post-buckled state as well as hysteresis behaviour. Also, the restoring force and the tangent stiffness varies depending on the temperature of the shape memory alloy. By applying these characteristics to a vibration isolator for vertical direction, it is expected that high performance isolator would be realized. That is, by combining post-buckled shape memory alloy plate with a general linear spring, of which spring constant is tuned so that the negative stiffness of the shape memory alloy plate would be just canceled, quasi-zero stiffness would be realized. Finally in this report, we propose the conceptual design of an isolator using post-buckled shape memory alloy and the isolation performance is experimentally investigated.

In late years production of commercial washing machines has been increasing. There is a problem with washing machines, eccentrics in a drum causes vibration, which leads to noise. In foregoing studies, an anti-vibration device has been utilized to damp vibration of washing machines. However, it is not enough to reduce the vibration. Washing machines therefore require a novel external vibration isolator. Also, the controlled object varies depending on the amount of washing clothes and washing mode and like. It is therefore important that the control device has robustness. In this study, we propose an external vibration isolator applying “Double-skyhook effect” for washing machines for business. We carried out simulations in order to demonstrate effects of the method. The most intense noise occur when the drum rotation speed is 11-20 Hz. We therefore check vibration isolation performance of 1120 Hz. A washing machine equipped with the proposed device was excited with chirp signal. The simulation revealed that the force acting on a floor was smaller than that of a conventional device by 60.6% in RMS. Also, even if the parameters fluctuated, the vibration isolation performance did not change. The results indicated that the proposed device was effective to damp the vibration and that the control device had robustness.

This research presents a novel thin-walled tube with pairing origami pattern as an energy absorption device of automobiles called side member. The characteristics of origami model were estimated with FEM analysis. The initial shape of the origami models is determined by three parameters. The results of numerical simulation of the dynamic axial crushing of the pairing origami models show that compared with conventional tube, the pairing origami patterns model exhibit a lower initial peak force and more uniform crushing load. The amount of energy absorption per mass was lower than conventional model, but close values were obtained. Considering that the manufacturing cost is as cheap as the conventional model, it can be said that this origami model is very suitable for a side member.

In recent years, there is a great need for lightweight, high stiffness structural technology that can realize fuel efficiency improvement as CO₂ reduction measures to prevent global warming. For example, honeycomb panel as lightweight and high stiffness panel is widely applied into various structure. However, honeycomb panel, which needs glue process, is very weak for shear stress and hot temperature. Also rapidly developing home delivery industries need reusable / absorption buffer materials. Therefore, innovative high stiffness structure technologies have been required. In response to these needs, we developed Assembly Truss Core Panel (ATCP) by using origami forming, suggesting the possibility to make much wider range of structure than before, which was reported as lightweight, high stiffness structural technology in 2014. In this paper, we present not only Paper/PP (Polypropylene) shock absorbing buffers as reusable ATCP with no glue, but also studies based on experimental tests by using prototype ATCP and FEM analysis.

Box in Assembly Truss Core Panel (BATCP) has been developed as a cushioning material as a box replacement for honeycomb boards as a part of origami engineering research. The superiority of BATCP as a cushioning material has already been described in detail, so it is omitted. ATCP consists of tetrahedron and octahedron half, filling them in a box. iPS cells, blood, grapes, strawberries, eggs etc are placed inner each tetrahedron and octahedron half. In other words, in this research we consider BATCP to have both roles as cushioning material and carrying box. As transportation, we are considering cars, boats, planes. Also, in depopulated areas, we are thinking about carrying with drone. Each of the above-mentioned objects to be transported has a frequency band to be avoided as much as possible. For this reason, we propose a suspension to reduce the transfer characteristics in the frequency band in question. Here, as a first report we will show the direction of a series of research and carry the BATCP on the drone and observe how is inside of BATCP at the time of the fall.

Current vehicle energy absorbers have two defects during collision, such as failing to achieve an ideal collapse (only 70 % collapsed in its length) and high initial peak load. It is because present energy absorbed column is the most primitive from the point of Origami structure. We developed the column so called Reversed Spiral Origami Structure; RSC which solves these 2 defects from Origami engineering. However, for RSC, the manufacturing cost of hydroforming in the existing technology is too high to be applied in real vehicle structure. To address the problems, a new structure, named Reversed Torsion Origami Structure (RTO), has been developed, which can be manufactured at a low cost by using simple torsion of Origami engineering. This structure is possible to replace conventional energy absorbers and expected to be widely used in building structures.

We have studied the sound quality improvement of the classical guitar. The running-in of really playing on the guitar as well as the manufacturing process of guitar gives the large influence to the sound quality. It is called an aging effect. It is important that the behavior of the aging effect is considered on the manufacturing process. But the result of over-aging treatment causes, sometimes, the poor sound quality. The mechanism of over-aging is open here.

In recent years, demand for a toilet noise reduction has been growing with an aging of population in japan. The purpose of this study is to develop the active noise control (ANC) system for a toilet noise. We proposed the toilet seat ANC system, in which the control sound is radiated to the inside of toilet bowl through the slit hole of the toilet seat. In this paper, the effectiveness of this proposal system is experimentally examined in the case of closing the lid of toilet. In the experiment, measurement of noise reduction characteristics and the sound visualization of toilet model using probe microphone were carried out. The results of this study shows that the noise-reduction effect was obtained maximum 49 dB at the error microphone and maximum 14 dB at the measurement microphone, in control for pure tone. From the result of visualization, noise-reduction effect was obtained in the local space of the error microphone position, however in external sound field, noise-reduction effect was hardly obtained depending on frequency due to the influence of transmission sound from the internal sound field.

In recent years, earplugs with analog acoustic band pass filters have been suggested. These earplugs could let workers in noisy factories to protect their ears and, at the same time, to hear the necessary sounds for communicating with colleagues, noticing danger alarm sounds, and detecting equipment failure noise, etc. However, some doubt has been still cast upon sufficient protection of the workers' ears particularly in low frequency range because of the relatively wide passing frequency ranges of sounds. There has been a clear need for the earplugs which could finely control the passing amount and range of sounds appropriately for each working environment. For fine tuning of resonant frequencies, we propose the simple structured earplug implemented with the filter consisting of a micro-orifice, a flexible elastic plate and a small weight. In current study, first of all, the frequency response of the proposed earplug is theoretically modeled by the transfer matrix method with each consisting component. Secondly, the theoretical model is tested experimentally. We obtained the results, which confirm the validity of the theoretical model. It has been also clarified that the proposed earplugs have the capabilities to insulate noise sufficiently in low frequency range and, at the same time, to efficiently pass 1k-2k Hz ranges of the sounds. Further fine tuning could be expected, by changing the detailed properties of the components.

Lightweighting, with respect to structural design, is required to reduce environmental impact. However, typical lightweighting requirements conflict with noise and vibration (NV) performance. To satisfy both lightweighting and NV requirements, vibro-acoustic metamaterials are being investigated as innovative alternatives. These metamaterials have wave-filtering characteristics, referred to as bandgaps, caused by structural periodicities. To apply vibro-acoustic metamaterials to engineering applications, it is important to adequately address their finite periodic structures. This paper presents an analytical model of wave transmission to determine the bandgaps of finite periodic structures. To understand the formation mechanism of these band gaps, a one-dimensional waveguide model is employed, and block diagrams of elastic wave propagation inside periodic structures are constructed. Finally, a metamaterial with structural periodicities caused by distributed local resonators is optimized to minimize the transmission ratio of elastic waves.

In this study, we made the acoustic meta-materials for changing sound transmission property in semi-finite field. By arranging apparent density of the materials distributed over the aperture through which the wave penetrated perpendicularly, the sound transmission path could be inclined from the nominal axis of the wave front. At first, we devised several patterns of the acoustic meta-materials. The first pattern is formed as a series of slits. The second pattern is a two-dimensional array of square props. The third pattern is an array of three-layered slits. The wave propagation analysis in two-dimensional free field incorporating the material was performed using the finite element method. We found from the simulation that all of three types affected the sound deflection. We then conducted sound field measurements for the acoustic meta-materials. Consistent results have been obtained in experiments. However, it was found that the equivalent sound velocity distribution is not linearly distributed in the width direction of the acoustic meta-materials, and the wave front of the interference sound wave after the acoustic meta-materials transmission is disturbed. Therefore, we devised a new acoustic meta-material in which the equivalent sound velocity distribution changes continuously and linearly. By performing simulation using this acoustic meta-material, we could confirm the deflection of the regular wavefront.

We propose a topology optimization method based on a high-frequency homogenization method for the design of acoustic metamaterial that exhibits a desired dispersion relation. Negative refraction, which is one of the most typical phenomena in acoustic metamaterials, is achieved by obtaining the desired dispersion relation of metamaterial via topology optimization. First, the high-frequency homogenization method to express the dispersion relation of metamaterials is briefly explained. Next, optimization problem based on the high-frequency homogenization method is formulated so that the optimized design has a desired dispersion relation which satisfies conditions for negative refraction. A level set-based topology optimization is introduced to solve the optimization problem, and two-dimensional numerical example is provided to show the validity of our proposed method.

An acoustic metamaterial sound-insulator based on Helmholtz resonators is developed by using light weight plastic foam. Small Helmholtz resonators are embedded periodically within the sub-wavelength throughout the plate of plastic foam. This plate of plastic foam covers an elastic plate with an air gap and a double-wall insulation system is organized. This system exhibits extraordinary high sound transmission loss in the frequency range between these two resonances compared with the sound transmission loss by a conventional double-wall insulation system. This characteristic can be realized since the equivalent stiffness of the air gap becomes negative in that frequency range. The theoretical analysis gives the expression of the equivalent stiffness of the air gap between the elastic plate and the insulator with resonators. Numerical calculations are also performed by using representative unit cell to demonstrate the acoustic performance of the developed system, an elastic steel plate of 1 mm is covered with a plastic plate of 35 mm thick where the resonators that has a resonance around 2 kHz. Air gap of 5 mm between these two plates gives resonant transmission loss around 800 Hz. The finite element analysis utilizing COMSOL Multiphysics gives higher transmission loss than a conventional double-wall from 0.8 kHz to 2.0 kHz. Measured transmission loss of the system is also higher by 10 dB than one by the conventional double wall without resonators.