This paper proposes a novel seismometer-type absolute displacement sensor aimed at detecting earthquake waves with a large magnitude and long period. However, since the measuring range of the displacement sensor is higher than the natural frequency of itself, it is difficult to detect a low frequency vibration below 1Hz using conventional seismic-type displacement sensors. In order to provide an absolute displacement detection which is capable of lowering the natural frequency and enlarging the detectable amplitude without causing a structural defect, the relative signals of displacement, velocity, and acceleration between a detected object and the auxiliary mass of the sensor are fed back into the sensor. In addition, phase lag compensation is inserted to adjust phase angles, which are below a frequency lower than 1Hz. It has been demonstrated that a developed sensor with a small size and lightweight has a detecting range from 0.2Hz to 10Hz for absolute displacement and velocity. As an additional advantage, the measurement displacement amplitude has been expanded to about 40dB (100 times) for detecting earthquake waves with large magnitude and long period

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This report describes the experimental results of three-axis accelerometer calibration where the sensitivity is defined by a matrix form. The accelerometer is a so-called MEMS accelerometer (Hokuriku). The excitation of the accelerometer is carried out using the three-axis six-DOF shaker (IMV). The reference is the accelerometers (JAE) which control the motion of the shaker. The target of the experiment is to investigate the possibility of calibrating the multiple numbers of accelerometers at one time. The accelerometers under test are installed on a thick metal base plate. The base plate is fixed on the specimen table of the shaker. The attention was paid to the dependency of the measurement on the position of DUT in the plate, table and the quality of the motion generated by the shaker. One of the fundamental properties of the semiconductor accelerometers is the high volume of their production. On the other hand, the traditional method of calibration stated in ISO standards such as 16063 series can handle only one-axis accelerometer at one calibration using the one-axis shaker. Applying the conventional method will surely introduce the high cost. Quantitative application of semiconductor accelerometers requires a new technique of efficient calibration that enables both high accuracy and low cost. The lack of the technique might be one of the reasons why semiconductor inertial sensors are not utilized for the quantitative purpose. Typical quantitative application of inertial sensors is the measurement of the vibration to which human body is exposed during the one day working hours. If the vibration exceeds the specified value, the person in charge will go to prison. The sensors for this application are either three-axis or six-axis depending on the part of the human body.

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The authors' group has been developed an LDA flow rate meter based on laser-Doppler anemometer (LDA) for an instantaneous fuel injection rate measurement. This flow rate meter that does not affect the downstream spray can realize the simultaneous measurements of the dynamic fuel injection rate and of the spray characteristics. The transient flow rate can be useful to understand the spray characteristics. The LDA flow rate meter only measures one point time-series velocity on the center of circular pipe. It provides instantaneous time-series flow rate and integral mass of the fuel flow. In this paper, the LDA flow rate meter measured the high pressure injection system for the direct-injection engine. The pipe diameter of the measuring section of the LDA flow meter is tested for improving the measurement accuracy of the high pressure fuel injection rate. In the measurement, the fuel pressure is changed from 5MPa to 20MPa and injection time is changed from 0.5ms to 5ms. The integral masses by the LDA flow meter are compared with the results by a mass balance.

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In order to correspond to the regulations on the exhaust gas from diesel engines which becoming increasingly strict, fuel injector makers have been earnestly engaged in the development of super high pressure injections and multiple phase injections. To improve the combustion even better, exact understanding of the injector's characteristic which decides the accuracy of the injection is "must". By using a high-strength Co-Ni alloy for the measuring tube material and making the shape an oblong dual loop with no weld on the wet part, we have enabled the super high pressure (200 to 300MPa) and extra low mass flow measurement at the injector inlet, which had been asked for years but never been achieved, with our new type Coriolis Flowmeter. The technology and expected developments are explained in the following.

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Pressure diagrams represent important data, given that indicated mean effective pressure (IMEP), maximum in-cylinder pressure, heat release rate, and which directly expresses volume of work for each cycle, can be derived from them. Generally, in measurement of pressure diagrams, piezo-electric pressure sensor is used together with charge amplifier. However, the high-accuracy pressure sensors used in engine development have problems in terms of sensor life and mounting in the combustion chamber. So, in this paper, because of solving a problem, the prototype piezo-electric sensor to mount the outside of engine was manufactured. A present method of employing prototype sensors outside the combustion chamber to measure signals originating in combustion in the cylinders to determine the equivalent IMEP, which is strongly correlated with IMEP, would be calculated. In order to accurately determine IMEP, it is important that the detection of the 1st- and 2nd-order frequency components of engine speed. Measuring system using prototype sensor was improved low frequency characteristics owing to high sensitivity and high insulation resistance of prototype sensor. The prototype sensor mounted cylinder head of a four-stroke cycle single cylinder side valve engine and measured equivalent IMEP, the correlation coefficient between IMEP and equivalent IMEP was about 0.99. In the same way as single cylinder engine, the prototype sensor mounted cylinder block of a four-stroke cycle multi-cylinder engine and measured equivalent IMEP, the correlation coefficient between IMEP and equivalent IMEP was about 0.96. Therefore, the present method can expect to apply multi-cylinder engine.

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Internal combustion engines are required to use various fuels. A conventional MAP based engine control system is not suitable for achieving stable operation and high thermal efficient operation for various fuels. Authors have been developing the engine control algorithm to realize fuel flexibility by employing experimental rules and a closed loop control using in-cylinder gas pressure. In this study, in order to improve fuel flexibility of engine control algorithm and to confirm the experimental rules, availability of calculation results with elementary reactions for the algorithm is investigated. Availability of instant crank shaft torque for a feedback sensor is also investigated. The result shows that the modified engine control system employing laminar burning velocities calculated from elementary reactions and the torque feedback loop can keep stable operation when fuel lower heating value varies during engine operation.

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In this study, for considering effective countermeasures toward vibration of drum type washing machine through an experiment with small man-hour, main drum vibrations for spin-drying were analyzed and principal parts affecting the main vibration were selected through an analyze of actual vibration shape and basic vibration calculation. In the experiment, first order rotation vibration of each part of a drum type washing machine such as spring damper attachment point was measured for spin-drying mode. The result shows the vibration of a drum was high at 150 and 300 rpm. In addition, the drum was found to move along horizontal axis at 150 rpm and move along vertical axis mainly at 300 rpm by the actual vibration shape analysis. Then, the vibration response was calculated by applying a basic vibration theorem using spring constants and damping coefficients for horizontal and vertical axes of two spring damper systems supporting the drum by regarding these systems as the principal parts for the main vibrations. As a result, the resonance frequency and amplitude of calculated vibration response were similar with the measured vibration. From these experimental and analytical results, it was found that vibration of the drum type washing machine was affected by parameters of the spring damper systems mainly and the vibration is considered to be controlled effectively by changing these parameters, even though the drum connects various parts in actual.

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An application method of ICA on vibration of an automobile considering dynamical properties is introduced and its performance is examined through a numerical simulation using a half car model. The proposed method separates mixed signals considering dynamical properties, while original ICA assumes a static mixture. Also, methods for fixing order of independent components and amplitude are proposed for the estimation of road irregularity. By applying the proposed method, road irregularity with information of amplitude is estimated without knowing parameters such as mass and spring constant.

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A bicycle is a popular vehicle for a lot of people by the low price and the easy maintenance in comparison with a car and a motorcycle. In order to expand the popularity of the bicycle, improvement of the ride comfort is necessary. In this study, subjective evaluation tests and acceleration measurements using many kinds of bicycle were performed to quantify the ride comfort and obtain which part and frequency have high contribution to the ride comfort. In the subjective evaluation test, the vibration feeling of the saddle was found to correlate with the ride comfort very much, and through the acceleration measurement of the saddle, both vibrations of vertical and horizontal directions affect the ride comfort. But the influence of the vertical vibration was higher than that of the horizontal vibration. The ride comfort calculation method was developed by considering these characteristics. Next, to verify the reliability of the ride comfort calculation method, saddle vibration of a city bicycle was reduced by modifying the saddle spring and the frame structure. As a result, the ride comfort was evaluated better and the degree was very similar with the predicted level by the ride comfort calculation method. From these results, the ride comfort of bicycle could be quantified with high reliability.

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Automatic platooning is expected to be an efficient method to solve problems such as environmental issues and traffic problems in the transportation field. A vehicle controlled by automatic platooning is required to obtain proper parameters, which depend on driving conditions. Estimating of the vehicle parameters is necessary because the performance of the automatic platooning control is affected by a change of vehicle parameters. Among of vehicle parameters, yaw moment of inertia is important parameter during lane change or cornering to control the vehicles to maintain the driving stability. In this paper, the method to estimate yaw moment of inertia is proposed using GPS measuring system. Validity of the proposed method is shown through the experiment.

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Composite materials have been employed in many sporting gears. Especially, laminated composite materials are used for the golf club shafts. The purpose of study is to present the two-dimensional swing simulation of the golf club refereeing the swing image of the golf swing robot to clarify the deflection of the swinging golf club shafts. Firstly, a finite element model of golf club which consists of the simplified golf club head and the laminated composite shaft is presented. And, it is proposed that the two-dimensional swing simulation of the golf clubs using the relationship between the time and the angular velocity of the grip of golf club estimated from the swing image of the golf swing robot. Next, from the results obtained by the proposed swing simulation, the validity of the grip position of the golf club is clarified. Finally, the effects of the stacking sequence of the golf club shaft and the swing speed to the deflection of the shaft during the swing are examined, respectively.

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In this paper, a new perturbation method is proposed, and is shown that the correction vector can be calculated shorter than ever. And, the computing efficiency of the response surface optimization method could improve greatly by applying perturbation method with complementary term to example analysis in the optimization of vibration characteristics by the response surface methodology and by finishing eigenvalue analysis which takes most computing time just once. Moreover, the validity and effectiveness is examined by examples by inducing approximately estimated formula of the vibration response value based on orthogonal polynomial. Lastly, it is shown that the computing time is shorten greatly compared with former method by applying this method to analysis of optimization problem of vibration characteristics.

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This paper presents the free vibration analysis of the sandwich plate composed of isotropic material and viscoelastic material. For this purpose, the parameter identification of the stress-strain relationship of a viscoelastic material is carried out first by using fractional derivative model, and then natural frequencies and specific damping capacities of the sandwich plates are obtained numerically by using the Ritz's method based on the Discrete-Layer Theory (DLT), Higher-order Shear Deformation Theory (HSDT) and Classical Lamination Theory (CLT). Finally, the experimental study is also carried out by using the experimental model analysis, and the applicability of the analytical models in the vibration analysis is discussed from the comparisons of numerical and experimental results.

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Asymmetric laminates of fibrous composites have strong elastic and thermal anisotropic properties, resulting in the curved surfaces caused by residual thermal strain during curing process. Specific asymmetric laminates indicate bi-stable states in terms of surface shapes, and these bi-stable states enable large deformation with relatively small energy input. This becomes an advantage when the asymmetric laminate is applied to the aerospace structures such as a morphing airfoil. The present paper first reveals occurrence criteria of bi-stable states for asymmetric laminates. In-plane buckling strengths are employed as an index of occurrence and calculated for plates with different width-to-thickness ratio and lay-up configurations. Then, vibration properties of bi-stable composite shells are evaluated by using both numerical study with the Ritz method based on Donnel-Mushtari theory and the experimental modal analysis technique. The numerical and experimental results show that there are some relations between the buckling strength and the occurrence of bi-stable states within plates having specific lay-up configurations, and asymmetric laminates with bi-stable states indicate different vibration characteristics before and after snap-thorough deformation.

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The present study aims to optimize vibration characteristics of the fibrous composite plate with curvilinear fibers. Curvilinear fiber shapes are defined by the projections of contour lines for the surface which is expressed by multi-spline function. The curved surface of spline interpolation is defined by 25 data points, and their heights (z coordinates) are used as the design variables. The plate is limited to symmetric and balanced layup. Fundamental frequencies of the plate are calculated by an originally developed finite element code with iso-parametric 8-node elements. The optimization is carried out by applying a simple genetic algorithm with the maximum curvature constraint employed as the practicality index in the manufacturing process. Five different sets of boundary conditions are used in numerical experiments. Optimization results show that the curvilinear fiber shapes result in different shapes and higher fundamental frequencies for all boundary conditions, as they are compared to previous results where cubic polynomials are used to define for fiber shapes.

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The present study proposes an optimization method of laminated CFRP plates with variable thickness. The objective function is the fundamental frequency calculated by the originally developed finite element code with a 4-node rectangular (ACM) element, and design variable are placements of elements with reinforcement layer. A simple genetic algorithm method is employed with elitist tactics as an optimizer. The obtained plates with optimum placement of reinforcements and optimum fiber orientation angle result in the highest fundamental frequency among representative models. Then, based on the optimization results, the test specimens are fabricated by using hand lay-up and vacuum curing technique with pattern paper which keeps thicknesses difference clearly. Measured frequencies and modes shapes agree well with the calculated results and the fabricated optimum plate also indicates the higher fundamental frequency than other representative ones. Furthermore, the optimum variable thickness plate yields higher frequency compared with the homogenous thickness plate due to its small mass. This observation demonstrates an advantage of the variables thickness plate in terms of vibration characteristics.

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The modal analysis is applied both experimentally and numerically to study vibration characteristics of a symmetrically laminated rectangular plate with point masses attached on the surface. The problem is solved numerically by using the Ritz solution, which is derived theoretically from the functional with the kinetic energy of the added point masses, and the results are obtained to study the effect of the point masses on vibration behavior. Then, the experimental modal analysis is used to measure the natural frequencies and mode shapes. The two sets of results are compared and turned out in good agreement. Subsequently, the lay-up design problem is considered to maximize the fundamental frequencies by use of the layerwise optimization (LO) approach. The design variables are taken for a set of fiber orientation angles in the symmetric layers.

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Experimental results are presented on vibrations of a rectangular plate with an in-plane elastic constraint. One of the plate edges is clamped by rigid blocks. The other three edges are simply supported. The simply support edges are connected with elastic springs and are movable in in-plane direction. Effects of in-plane asymmetric force on nonlinear vibrations are investigated. Under the in-plane asymmetric force, the deflection of the plate shows the type of a softening-and-hardening spring. Under periodic lateral excitation, non-periodic responses are obtained in the typical frequency regions. The non-periodic responses are examined with the Fourier spectra and the maximum Lyapunov exponents. It is found that the chaotic responses are generated from internal resonance coupled with the lowest and second modes. In-plane asymmetric force increases the maximum Lyapunov exponents.

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Experimental results are presented on flow-induced vibrations of a rectangular plate constrained by a stretched string. The plate is clamped at the bottom and deformed to curved configuration by a stretched string at tip ends. Vibration responses of plate are measured, with and without constraint by a stretched string. Changing the angle of the flow, strain of the plate is measured. Maximum strain is obtained when the wind is blown nearly parallel to the plate. Although the strain of the plate constrained by a stretched string is small, the amplitude has broadband spectrum. Chaotic responses are generated by the flow-induced vibrations. Dominant frequency components of the vibration responses correspond to the natural frequencies of the plate. Chaotic responses are examined by the Fourier spectra and the maximum Lyapunov exponents. Contributions of vibration modes to the chaotic responses are inspected by the principal components analysis.

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This report presents a numerical method to investigate the frequency response of shell structures. Transfer matrix method is a useful approach to analyze the vibration problem of continuous systems because of its computational efficiency. However, when we use the transfer matrix method to calculate frequency response of the shell structure, exciting force is limited to a line force and applicable object is also restricted. For this reason, we use a method to calculate modal parameters from free vibration analysis by using the transfer matrix method. We have applied this method to the frequency response of shell structure. Comparing the results obtained from this method and ANSYS, characteristics of both frequency response have a good agreement.

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The floating roofs are used in large cylindrical storage tanks to prevent evaporation of oil. The single-deck floating roof, considered herein, consists of a thin circular plate called "deck" attached to a buoyant ring of box-shaped cross section called "pontoon". The deck plates are deformed to create waves and they are subjected to cyclic bending due to wind load. This may lead to initiate fatigue cracks at the welded joints. It is important to know the characteristics of waves in the deck plate. The authors have reported the CFD analysis of a cylindrical storage tank due to uniform wind in another paper. This paper presents the axisymmetric finite element analysis for the sloshing response of the single-deck floating roofs in a cylindrical storage tank using the CFD results as the load condition. It is assumed that the liquid is incompressible and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The basic wave characteristics of the deck plate, such as frequency and amplitude is investigated.

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The finite element method is applied to buckling analysis of cylindrical shells partially subjected to external and internal liquid pressures. The axisymmetric shell element is used with displacement field within each element is represented by Fourier circumferential components. The shells are assumed to stand vertically with the lower and upper ends clamped. The analyses are performed for a wide range of the geometric parameter Z and the buckling liquid heights are obtained. The effects of the internal liquid height and the difference of mass density between external and internal liquids on the buckling liquid height are investigated. Based on the results of the finite element analyses, the simplified equations to calculate buckling liquid height with the effect of internal liquid are established.

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The present study deals with the imperfection-sensitive non-linear buckling behavior of cylindrical sandwich shells consisting of a steel core bonded with FRP skins. Steel cylindrical shells when exposed to the marine environments show their vulnerability to corrosion. When carbon fiber reinforced polymer are collectively used for corroded steel shells, the mechanical and anti-corrosive properties as a new composite structure will increase tremendously. This paper discusses the effects of imperfections on the nonlinear buckling under axial loading and also proposes an alternative conservative design estimation technique based upon the so-called reduced stiffness buckling theory.

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Theoretical studies were conducted to clarify hydroelastic vibrations of a tank filled with liquid and flexible space structure under low-gravity. The satellite has a central rigid body with tank filled with liquid fuel and two flexible appendages like solar array. The liquid in central body were treated spring-mass system and the appendages were considered as the Euler-Bernoulli beams joined to the central body with a torsion spring. Assuming the system vibrates in the axial direction of a tank, we derived the frequency equation by Rayleigh-Ritz method. Coupled natural frequencies were obtained as an eigenvalue. With increase in torsion spring constant, coupled natural frequencies increase.

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As represented by Miura-ori, origami has inspired various types of deployable structures. Usually, these Origami structures are designed under the assumption of "rigid folding", which means each plane is undeformable and connected with ideal joints. In this study, a new strategy for designing deployable structures are proposed by using partially elastic origami models. These new origami structures take into account the elastic deformation. It enables us to estimate the elastic energy through folding and unfolding process and to design self-deploying origami structures.

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Elegant 3D origami structures from a planar sheet have been presented by incorporating curved folding into the design. Sometimes they look like sculpture, and a new genre called curved origami are now being formed. However, relation between the curved origami and traditional origami using straight creases is not clear in theoretical bases. We construct curved creases consisting of very short (tending to infinitesimal) straight hinge like creases. In the present report, some origami samples for circular tubes surfaces and conical surfaces are introduced. In the second half, a fundamental design method of such forming collar in vertical form-fill-seal machine is presented by using curved folding without elastic strain.

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In this paper, a new technique is shown to obtain developed patterns of conical shells and circular membranes from ones of cylinders by using the conformal transformation. It enables to design foldable structures systematically, controlling angles among fold lines for maintaining advanced functions particular to origami such as foldability, expandability, inflatability and so on. Also, it is able to yield new saddle-shaped structures based on fluid flows. It is described the mathematical interrelation of developed patterns between cylinders and conical shells, and advantages on applying the mathematical technique on designs of origami structures. The method is to help us to imagine and model new shapes of structures for future application on engineering.

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Origami crease patterns became one of the most common ways to codify origami. They are easy to draw, easy to share and it shows, in just one picture, the structure of the origami base. But crease patterns do not show the reader how to fold itself, a task that can be very laborious and rely on trial and error. This work describes a system designed to find automatically a folding sequence given a crease pattern, so that beginners would have a more detailed guide to collapse the base and designers would have a base set of drawings to begin diagramming their creations. It uses graph pattern matching to find the occurrence of known folds and undo them, thus finding a sequence to unfold the model. The sequence is then reverted, achieving the desired diagram. By the present time, the proposed system only recognizes simple mountain/valley folds.

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In this paper, we study a method for designing flexible origami by solving the geometry and folding mode that satisfy infinitesimal rigid foldability constraints. We show design examples using an interactive design system based on the proposed method; the results include infinitesimally foldable (shaky) closed origami surfaces and quadrangle based origami, which are in generic cases static. Especially, a cylindrical shaky closed polyhedron has zero-stiffness property in an infinitesimal folding and traveling hingelines in a finite folding to a flat-folded state, which are potentially useful for energy absorption devices.

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The new mobility vehicles for individual usage called personal mobility vehicles (PMVs) are expected to be developed these days in terms of protection of the environment, support for an aging society and ensuring the right to mobility. For example, an inverted pendulum vehicle is one of the convenient vehicles used in pedestrian space. It is necessary for such a PMV used in pedestrian area to ensure pedestrian safety and comfort. In this study, in order to realize the behavior of a PMV to be friendly to a pedestrian, the driving assist system considering the personal space of a surrounding pedestrian is investigated. In this paper, as a basic study, we propose the behavior model of a PMV considering the personal space of a pedestrian. In the simulation, the affinity between a PMV and a pedestrian is evaluated. It was found that in the case that the personal space of a PMV is smaller than that of a pedestrian, the driving of PMV considering personal space of a pedestrian was effective. The level of the effectiveness was changed according to the width of a PMV. It was also found that the road width affects the effectiveness. When the road width is 2 [m], it is difficult to secure space of avoidance so that the effect of the PMV driving considering a pedestrian's personal space is limited. On the other hand, when the road width is 3 [m], the effect was more clearly confirmed.

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An inverted pendulum-type PMV (personal mobility vehicle) has been attracting attention as a low-carbon vehicle. For many people who like to use the PMV, ride comfort is important. However, ride comfort of PMV has not been focused on in previous studies. The vibration is one of causes that make riders feel uncomfortable. The PMV is unstable system and horizontal vibration may be caused by a stabilizing control. Additionally, vertical vibration may also be caused by road disturbances. This study analyzes the vibration of the rider's head in these two directions when the PMV runs on a road with disturbances in numerical simulations, and evaluates ride comfort with the frequency characteristics of the vibration. To consider human vibration sensitivity, the frequency weighting proposed in ISO 2631-1 is used as an evaluation standard. The improvement methods are proposed from both software and hardware, and it is confirmed that the proposed method can improve ride comfort.

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Recently, the people who need powered wheelchairs have been increasing due to its aging society. When people take ride in powered wheelchairs, riding comfort is very important. Acceleration and vibration are concerned with riding comfort strongly. In addition to riding comfort, wheelchairs must have good response to reference velocity because collision must be avoided. Therefore, we propose a control system which can reduce the vibration of body and achieve quick response. For reducing the vibration of body, we design feedforward input using Nil-Mode-Exciting (NME) profiler (which is called preshaping profiler). NME profiler is based on sine function, so control input has low pass characteristic. Then natural vibration of body is escaped. However, when the NME profiler is used as a feedforward input, it cannot compensate robustness about body's weight or friction. To deal with this problem, we design a wheel velocity feedback control added to the feedforward control. The effectiveness of the proposed method is verified by numerical simulations.

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Vehicles acquire longitudinal force, lateral force, and yaw moment to achieve desired movements by generating tire force, which is the friction force between the four wheels and the road. In this study, we formulate an optimization problem of seeking the magnitude and direction of tire force that minimizes the maximum μ rate (=tire force/friction circle) of each tire under restricted conditions to obtain the desired force and yaw moment of the vehicle. Subsequently, we propose two calculation methods to solve the optimization problem: one is based on sequential quadratic programming (SQP) and the other is based on the penalty function method. By numerical calculations, we show that each method can be used under certain conditions. Moreover, we obtain the number of calculations for each method and compare it with that for yaw moment optimization by the golden section method, which is another method for generating tire force efficiently. We show that of the three methods, the golden section method requires the least number of calculations under the conditions tested.

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This paper proposes an automatic driving of commercial vehicle by infrastructure design. Various automation technologies have been carried out in recent years. These include automatic car driving established with a number of sensors and actuators. This even enables to guide the vehicle to the destination by adding improvements to the infrastructure. Therefore, assuming the use for Park and Ride combined with valet parking, a concept of utilizing a simple automatic driving control by road infrastructure at places is introduced such as underneath the elevated railway tracks. Dynamic simulation model which can deal with the influence of road slope and free-steering is made. And dynamics of vehicle on slope is simulated for a fundamental consideration of dynamic characteristics of a vehicle. Finally, dynamics of vehicle was simulated with three road surface types of cross-section, and the possibility of automatic driving is shown by specially designed road shapes.

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Ultra precision apparatus like semiconductor producing equipment needs high accuracy at manufacturing. Therefore active isolation systems to avoid vibration transmission from vibration sources to the precision apparatus are very important. Vibration characteristics of an isolation table varies as any elastic loads are put on it. Then the isolation performance is degraded due to the change of the characteristics. Therefore, the controllers for the active isolation table should be designed taking account of elastic loads. For this purpose, a dynamical model must be identified that takes the dynamics of elastic loads into consideration to such controllers. In this research, an experimental active isolation table with an elastic load is built. Its dynamical model is identified and a feedback controller is designed by using the model. Property of the obtained controller is qualified through computer simulations.

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It is well known that the servo system sometimes provides undesirable overshoot in transient responses for temporary disturbance such as the impulse disturbance. The response is caused from the action of the servo system which sweeps out the state variable of the integrator. In such cases, the transient response performance becomes worse in comparison to the one by the regulator system. In the present paper, a method for improvement of the transient response of the servo system based on the disturbance estimation and switching the control action is proposed. The effectiveness of the proposed method is verified by the pneumatic isolation table by numerical simulations.

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In feedback control of mechanical systems, various kinds of sensors are used, and usually each sensor has its advantages and disadvantages at the same time. For example, accelerometers are suitable for measuring relatively high frequency motion, and displacement sensors are suitable for measuring relatively low frequency motion. In order to utilize only advantages of each sensor, sensor-fusion technique is used in many fields. However, when the sensor fusion is used for feedback control problems, it requires both signal filters and feedback controller. The signal filers are used to generate physical values from various sensor measurements, and then the feedback controller uses these generated values for control. This paper proposes a concept of "Controller Fusion". Controller fusion is the way to design controllers which works as both signal filters and feedback controllers. Therefore the control system design process becomes simpler than the sensor fusion, and also good motion control performance is obtained in wide frequency range. In this paper, first the concept of "Controller Fusion" is described, then the experimental results are shown for a 3-dof electric shaking table, and effectiveness of the controller fusion is evaluated. Finally some discussions for future practical systems are related.

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In recent years many engineers research for breakdown process of a building by vibration testing in order to grasp aseismic capacity. A shaking table needs to operate correctly for having experimental results. However, in many cases a shaking table does not move accurately because of reaction force of specimen on the shaking table and cross-axis sensitivity. So this study shows the control method of the shaking table as one of solution. More specifically, this study presents design of displacement control system with good tracking performance and good disturbance rejection performance. This controller is designed by Dual Model Matching control method. The effectiveness of the control method is tested by applying to 3-DOF electro dynamic shaking system.

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A simple dynamic model will be effective to determine the properties of protection devices because it is useful to understand the essential dynamics of the occupant in car crash. This paper describes an optimal restraint method in frontal car crash by using a reduced-order dynamic model based on a human occupant finite element model having age-specific characteristics such as bone stiffness and tolerance of the body. The restraint force is determined so as to minimize the maximum thoracic deflection, which is one of the representing injury criteria in frontal car crash, while the maximum thorax and pelvis displacements are restrained. Simulation results clarify that the optimal restraint force is effective for reducing the maximum thoracic deflection.

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This paper describes an active control system intended to minimize the vertical vibrations transferred from the vehicle seat to human body. This system had been evaluated by the human model which had head, body, thigh, shin upper arm and fore arm. However, the vibration of the road surface is transmitted to the occupant of a vehicle while under the influence of resonance in the vehicle. Traditional vibration model has been input from the vibration under the seat directly. If it takes into account the effects on the behavior of the vehicle occupants. Therefore, Occupant behavior may be considered to be more complex. Therefore, we developed a vibration model of passenger-seat-steering wheel-pedals system. The body has six parts such as head, chest, thigh, shin, upper arm and lower arm. And vehicle has three parts such as sprung mass, front unsprung mass and rear sprung mass. We have investigated the reduction rate of the vertical vibrations on the head, shin and lower arm which are important parts on operation while driving. From the results, it is shown that the validity of this model and that relationships between the reduction rates and the mechanical properties of the each seat cushion for frequency band.

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Vibration by road surface gives the damage or deterioration of luggage. In terms of protecting the quality of the luggage, the development of technology of vibration suppression is demanded. Therefore, studies on the active suspension have been carried out actively. However, the parameter changes of the weight of the luggage is larger, suspension performance varies by the weight of the luggage. Therefore, it is effective to develop robust controller for the active suspension based on the weight of the luggage. As robust control design to parameter variation for such a control object, Simple Adaptive Control is proposed. Simple adaptive control is a system design method based on a control theory by tuning the adaptive gains in the controller. Control gains of the controller are adjusted automatically to adapt to changes to the weight of the luggage, it is possible to maintain good performance to prevent vehicle vibrations. This study confirmed that the active suspension using a simple adaptive control have better performance than passive suspension.

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Complicated three dimensional vertical elastic vibrations tend to have influence on riding quality in recent railway vehicle carbodies. We proposed a vibration reduction method using active mass dampers (AMDs) to reduce such vibrations and its feasibility has been confirmed. As a next step, we are trying to realize more practical AMD system with smaller and lighter actuators. This paper describes the excitation test using test vehicle in the rolling stock testing plant at RTRI to verify the effectiveness of the vibration control using the light AMDs with moving mass of 35kg and 36kg. The peaks corresponding to two target modes are reduced successfully when an AMD is applied in the all wheel simultaneous excitation test and two AMDs enable more effective vibration control. The root mean square (RMS) values of acceleration from 5Hz to 20Hz were reduced around floor center in the excitation tests simulated running corresponding to three type velocity.

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The authors have been studying on the method for reduction in contact force fluctuation between catenary and pantograph using variable stiffness devices. The normal pan springs of the pantograph are replaced by the devices utilized in this study. It is possible to improve the current collection performance by varying the stiffness of the device in such a way that the peak frequency of pantograph's mechanical compliance is consistent with the dominant frequency of the disturbance to the pantograph. We produced a prototype of the device and mounted it on a pantograph. The device is composed of two air springs and is capable of varying its stiffness by changing the air pressure. However, its stiffness is biased by the rubber parts of the air springs so that the controllable peak frequency range of the pantograph's mechanical compliance is limited only in higher frequency region. The rubber parts cannot make thinner to reduce its stiffness contribution to the device because it is necessary for the device to retain pressure capability. In order to overcome abovementioned problem, we propose the other type of variable stiffness device which actually is a pneumatic cylinder. The device has lower stiffness without losing pressure capability. The pantograph with this device indicates better performance in terms of the controllable peak frequency range of the mechanical compliance.

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Force redistribution method for compensating actuator-breakdown of vibration isolation tables is studied in this paper. Force of actuators can be adjusted by stepping motors in the regulator when some actuators are breaking down. The vibration isolation table in this study is supported by 8 pneumatic actuators, and has redundant number of actuators against degrees of freedom of motion. We propose a redistributing method of force which utilizes redundancy of the actuators. Effectiveness of the proposed method is examined by simulation.

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In this study, we analyzed the vibration and noise in the case that a cylinder was impacted axially, and proposed an effective method to suppress the vibration and noise. A cantilever cylinder was chosen as the subject, and the vibration of the cylinder and the sound pressure around the cylinder were investigated in the case that a weight collided with the cylinder axially. From the experimental results, it was shown that in the case of the axial impact, the bending vibration modes were excited by the eccentric collision and the components of the bending modes were dominant in the noise data. Then we proposed a noise suppression method, i.e., attachment of a small jig around the bar. It was shown that an effective suppression effect can be obtained when the jig is attached near the free end of the bar with small clamping torque.

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Vibration control of an elastic structure subjected to horizontal harmonic excitation by using two square liquid tanks is investigated. These two modes are nonlinearly coupled with each other due to the autoparametric interaction because the natural frequencies of two sloshing modes (1,0) and (0,1) in a square tank are identical. When utilizing the autoparametric interaction of two square tanks, the performance of tuned liquid dampers (TLDs) could be significantly improved because two peaks on the both sides of the tuning frequency are simultaneously suppressed. In the theoretical analysis, the equation of motion for the structure and the modal equations for sloshing are derived considering the nonlinearity of sloshing. Then, van der Pol's method is employed to determine the frequency response curves. The influences of the system parameters, such as the aspect ratio of the tank cross-section and the liquid level, on the response curves are examined. Hopf bifurcations sometimes occur and amplitude modulated motions appear depending on the system parameters. It is found that utilizing two square tanks results in improving the performance of TLDs.

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The nondestructive testing for structures such as poles or cables has been developing. However, since current techniques are generally visual inspection or point measurement, they require an automatic and efficient system for nondestructive testing. Guided waves can spread a long distance without energy loss. That suggests a possibility of efficient nondestructive testing of large-scale structures such as pipes and wires. However, there are some problems for practical use. For instance, distinguishing contribution of a particular mode from receiver signals is incomplete, and moreover, mechanisms of guided waves in wires are further difficult because of its complex geometry. The goal of this research is to establish a flaw detection method using a particular mode of guided waves in a seven-wire strand whose each wire is further composed of nineteen-stranded fine wires known as 7×19 type wire. We first verified generation of guided waves in a rod and a wire under excitation at a specific frequency from experiments. That suggests modes of guided waves in the experimental results can be determined by the theoretical value such as the frequency, the group velocity and displacement distributions. Moreover, we applied the finite element method to analysis of wave propagation in a cylindrical center strand and in a helical peripheral strand. According to these results, for general lay angle, modal exchange of guided waves did not occur in the helical peripheral strand though it has complex geometry and the longitudinal mode of guided waves was less damped than the flexural mode of them.

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Nondestructive testing is useful for maintenance of structures. Recently, nonlinear ultrasonic testing with subharmonic becomes attractive method of detecting the closed crack. However, the mechanism of subharmonic generation by the closed crack is not clear yet. This study investigates propagation of inclined incident ultrasonic waves through the closed crack and creates the two-dimensional model with nonlinearity. In our experiment, the closed crack was modeled as contact area of two aluminum specimens compressed. Four conditions were prepared by a combination of two incidence angle (30-degrees and 60-degrees) and of two compression force (3kN and 6kN). In each condition, after first finding a natural frequency from its frequency response, we analyzed received signals obtained under the excitation frequency twice the natural frequency, using the wavelet transformation. From the frequency response, not only the peaks of signals but also the natural frequencies were under the influence of the incident angle and the compression force. Moreover, from the analysis of received signals, 1/2-subharmonic generated if the incident angle was 30-degree and the compression force was 3kN, though 1/2-subharmonic did not generate in other conditions. According to these results, we introduced a two-dimensional model with a nonlinear spring normal to the contact area and with a nonlinear spring and a damper horizontal to the contact area. Specially, the nonlinearities of the spring in the horizontal direction are only odd powers. In conclusion, this two-dimensional modeling can be essential to understand mechanism of subharmonic generation at the closed crack under inclined incidence of ultrasonic waves.

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Analytical results are presented on nonlinear vibrations of a bowed-type beam deformed by stretched strings at both ends with a mode shape function approach. This procedure combines the procedures of modal expansion with finite element analysis. The mode shape function is introduced with the product of truncated power series and trigonometric function. The unknown coefficients of the mode shape function satisfy both of the geometric and dynamical boundary condition at the nodes of segments. First, the governing equation of the beam is obtained including the geometrical nonlinearity due to the stretch of the beam and of the string. Then, linear vibration modes of the beam are obtained under the condition of pre-buckling. Furthermore, applying the modified Galerkin procedure based on the linear mode to the nonlinear governing equation. Nonlinear periodic and non-periodic responses are calculated. The chaotic response of the beam is generated from the internal response of the sub-harmonic response of 1/4 order with the asymmetric lowest mode of vibration and of the principal resonance with the symmetric second mode accompanied by the dynamic snap-thorough.

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This paper develops a method of forced vibration analysis for a stepped cantilever beam with an elastically coupled rigid body at its intermediate point, according to the standard modal analysis. Starting from governing equations (one PDE, one ODE and boundary conditions,) the deflection function of PDE is then lifted into piecewise continuous functions at mechanical discontinuities. Using corresponding mode functions for the beam vibration and the rigid body motion, which are obtained in free vibration analysis, the problem is cast into solving a set of DAEs under boundary conditions. By establishing orthogonality and normalization conditions of the mode functions, a method of forced vibration analysis is finally derived. These conditions are considered as extended results of existing ones and main contributions of this work. Steady-state and transient responses can be computed analytically. The proposed method is primarily expected to serve as an alternative to FEM based vibration analysis, but it can also be utilized in designing vibration systems.

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