This paper describes an application study of Magneto-Rheological (MR) grease damper to a structure with three stories. MR fluid is known as one of successful smart materials whose rheological properties can be varied by applied magnetic field strength, and has been applied to various kinds of device such as dampers, clutches, engine mounts, etc. However, the sedimentation of ferromagnetic particles dispersed in MR fluid may take place due to the density difference between the particles and their career fluid. In order to overcome this defect, we developed new type of controllable working fluid using grease as the career of magnetic particles which might be held in its thickener network. No or little sedimentation was observed in MR grease whose characteristics could be controlled by the applied magnetic field strength. MR grease was introduced into a cylindrical damper and its performance was studied. As a result, it was confirmed that the damping force of MR grease damper could be controlled by the applied electric current to the coil in the cylinder. Furthermore, vibration response of a three-story model structure equipped with MR grease damper was investigated experimentally, and it was shown that MR grease damper works effectively as a semi-active damper.

View full abstract

Dynamic Vibration Absorber (DVA) is well known as one of the representatives of vibration suppression systems. DVA is classified to be passive system and has the advantage that it is reliable and inexpensive, but does not work effectively beyond the designed range. To solve this problem, Magneto-rheological elastomers (MREs) are adopted to DVA to make DVA with variable stiffness. MREs are one of smart materials whose rheological or viscoelastic properties can be varied by applying external magnetic field. In this paper, the stiffness controllable elastomer composites known as MREs are first fabricated and their field- dependent static and dynamic properties are tested as the basis of this study. The MRE is then applied to DVA to control the vibration of one-degree of freedom structure model. Experimental investigations show that the vibration of the one-degree of freedom structure that is exposed to base excitation can be effectively reduced by actuating DVA with variable stiffness.

View full abstract

Generally, a magnetic damper has a weak point that damping performance is relatively weak. The authors have been researching the high performance magnetic damper utilizing changes of the direction of magnetic poles or arrangements of magnets. In the present work, the design method of the high performance magnetic damper composed of a conductor plate and arranged rectangular magnets on its both sides is proposed. Using the modeling method the authors have been studying, when even number magnets with oppositely aligned magnetic poles are used and the area of total magnet is an almost same size of the conducting plate, the magnetic damper has highly performance. Furthermore, when the optimal number of even number magnets is chosen, it is analytically shown that the damping performance is the highest.

View full abstract

Many types of semiactive dampers that can have a variable damping force in order to control and reduce vibration efficiently. Most of semiactive damper have a dynamic function of switching viscosity or stiffness. In this study, a unique active damper that utilizes electromagnetic induction is developed. The active damper consists of a cylinder, piston, a by-pass pipe, electrodes, electromagnets and fluid. A resisting force is derived by the Fleming interaction across a magnetic flux and some electrodes in the by-pass pipe area. It is pointed out that the eight electromagnets are installed at around the by-pass pipe and enable to switch a value and direction of magnetic flux density. In this study, salt water instead of a functional fluid such as MR fluid. The test device of the by-pass pipe was partially manufactured in order to confirm the theory of electromagnetic induction, and to obtain adequate resisting force. Finally, the feasibility study of the damper is confirmed experimentally.

View full abstract

In this report, we propose a simplified vibration isolator utilizing buckled beam and investigate the basic properties of proposed isolator. The isolator consists of two thin plate beams jointed perpendicularly. One beam is fixed vertically to the base and the other fixed horizontally. The mass of isolating object is supported at the joint of two beams. When vertical down force was applied at the joint of beams, this beam behaves in the alternative of two buckling modes, that is, stable buckling mode and unstable buckling mode. From the numerical analysis of the restoring force and the local stiffness of two buckling modes, we adopt unstable buckling mode to the isolator. The unstable buckling mode enables the isolator to have the property of high static stiffness and low dynamic stiffness. This report shows the basic property of this isolator by the numerical analysis by FEM and the experimental results.

View full abstract

In this paper the authors propose a dynamic absorber for a pole structure, as like a traffic signal pole on an express highway, in order to not only dissipate vibration energy, and also obtain an electrical energy. To investigate dynamic property, a test dynamic absorber that consist of rare-earth magnet, solenoid coil and spring was manufactured. An electric power and a damping force are measured by a shaking table. Also magnetic flux density around the solenoid coil with the magnets is analyzed by using FEM, and output voltage is calculated. Vibration tests of the test absorber are carried out and the experimental results are compared with the calculated results. The dynamic absorber is installed on a 1/3 scales pole structure model of, and investigate frequency responses by the test dynamic absorber.

View full abstract

Liquid crystal polymer fiber reinforced plastics is applied to golf shaft. The vibration test of cantilever is carried out to reveal the differece of damping performance between CFRP and LCP-FRP golf shaft. From the result of this vibration test, LCP fiber has high damping properties. Next the paper presents effect of location of high damping material on damping performance. The damping ratio of golf shaft has been investigated by varying the location of high damping sheet from the fixed end of the structure.

View full abstract

Advantages of a cantilever-type dynamic absorber are simple shape, ease of manufacture and low-cost. In many past studies, the cantilever-type dynamic absorber is composed of lumped mass and zero mass plate spring or rigid beam and elastic fixation. However, the later has extra rigid modes, and these modes may become a source of unnecessary vibration. In this paper, we considered how to design and apply the cantilever-type dynamic absorber that consists of rigid fixed distributed mass system in order to absorb vibration of a cylindrical structure. Especially, a stator of a rotating machine as an example of the cylindrical structure is excited by electromagnetic force. And its circular vibration modes often become a problem. We conducted fundamental impact testing by using simple circular ring and cantilever. The testing results showed that the cantilever-type dynamic absorber is available to reduce the vibration of a cylindrical structure.

View full abstract

In this paper, we present the results of experimental and analytical studies of a particle damper with hollow steel particles in a nonlinear vibrating system. The principle behind damping is the removal of vibrating energy through momentum transfer and friction losses between particles and the cavity. An analytical solution based on the discrete element method (DEM) is presented. The experimental study shows that significant damping can be achieved through used of hollow particle damping. Comparison between the experimental and analytical results shows that accurate estimates of the rms response of a primary system can be obtained. The height of granular materials and the clearance ratio were calculated by the gravity method. It is shown that the response of the primary system is independent of the area of the damper cavity in the case of that the mass ratio and the clearance ratio are the same.

View full abstract

This report is a study of a vibration control device using collision of mutual vibrators. The device consists of plural vibrators made of a cantilever beam and a tip mass. Transient response of the primary system is suppressed by vibrators because the vibration energy of the primary system is dissipated by collision of vibrators. Authors previously reported the vibration control device which uses collision of two vibrators. It was shown that the largest vibration control effect is acquired when the collision cycle of vibrators agrees with that of the primary system. In this report, vibration control effects in case of three or more vibrators are examined by simulation. In addition, the condition of vibrators which makes the vibration control effect largest is searched by DE method and the effect in compared.

View full abstract

This paper describes the particle damper design, based on the analytical single mass damper model and experiments with smaller size steel balls. The effects of various system parameters - including mass ratio, particle size, cavity dimensions, intensity, and frequency of excitation - were investigated using a SDOF structure under harmonic force excitation when the vertical excitation is applied to the structure. The damper designs call for that the damped motions of the structure equipped with steel ball particle dampers become periodic as well as kept approximately equivalent as predictions by the analytical model. It is shown that the suitable size of steel ball and container dimensions were found to be selected for the combinations of mass ratio and excitation levels in the vicinity of the optimum range of system. Thus, the particle dampers with steel balls, with moderate mass ratios, can be very effective in attenuating the response of lightly damped structures.

View full abstract

This paper proposes a method improving precision of sound source identification by inverse acoustic analysis. The inverse acoustic analysis identifies a vibrational state for mechanical structures by measuring the radiated sound in many points and solving the inverse problem. In this analysis, the uniqueness of solution is not always guaranteed, and the problem is to avoid the instability of the inverse matrix in sound source identification. A numerical simulation is performed about a plate model, on which many point sources are assumed that radiate sound pressure by their vibration. Sound pressures are measured by many microphones and the inverse matrix is calculated from acoustic transfer functions. This paper presents two kinds of methods for changing the coordinates of measurement points in order to decrease the instability of the inverse matrix. One is the singular value sensitivity analysis and the other is the statistic approach by using normal distribution. Both methods are applied for the noise source identification of the plate, and the results are compared, and their features are discussed.

View full abstract

Damping in acoustics means to the sound absorption. To define the complex density means a viscous damping vibration of continuous system, and to use the concept of complex propagation speed and complex wave number, can explain the phenomenon of wave propagation with damping. The case of non-damping, when wave propagation is one-dimensional acoustic tube, natural mode is formed by overlapping of the traveling wave and the reflected wave, eigenvalue and eigen function is represented by real numbers. The case of uniform Rayleigh damping, eigen function becomes real and eigenvalues becomes complex. However, the natural mode is less likely to be excited due to distance decay. In this study, to reproduce the logarithmic decrement used to excite a natural mode by overlapping wave by uniform distribution excitations for distance decay. Measured complex propagation speed by the method of two types of measured after excitation of damped free vibration natural mode and distance decay measurement in forced oscillation, to pigeonhole the relationship between them.

View full abstract

Recently noise control performance is demanded with the exception of basic performance. Modal experiment should be conducted in evaluation. Now, structure excitation is the mainstream instead of acoustic excitation in method. Some acoustic equipment has been on the large and difficult to measure the input. But there is necessary to improve method for research the properties of vibro-acoustic system. Especially, modal separation need for in high modal density frequency range. Hence, it deliberates the modal properties that contribute largely to the acoustic properties by acoustic excitation. The input is measured by the speaker volume and internal pressure and the speaker is downsized. The acoustic excitation testing is conducted by the speaker to the vehicle. The method validation conducted by a reciprocity test. Next, the FRF by the structure response compared against the structure excitation. Finally, structure response and acoustic response are measured by acoustic excitation at the same time. This research reports the results and deliberation.

View full abstract

Air conditioner has become the necessities to create a comfortable living environment. On the other hand, it has been required reduction of noise and vibration in development of room air conditioner, because noise of outdoor unit becomes issues in an overcrowded area. There are four noises leading cause of noise given off by air conditioner. This study focuses attention on solid-born sound that is generated with frequency range of 100-500Hz. When it comes to this noise, installation of the refrigerant pipes, one of the transfer paths of vibration that contributes to noise, becomes an issue. However noise and vibration widely vary due to installation, solution that quantitatively reduces noise and vibration is not still presented. For such a problem, it is expected that it can effectively reduce noise and vibration by applying Transfer Path Analysis (TPA) that is applied to identify the path to countermeasure from among transfer paths that exist a lot from vibratory source to output points. Therefore, in this study, we apply TPA refrigerant pipes that issue is raised at the moment among the pipes existing in an outdoor unit. We perform structural modification of controversial pipe and try to reduce target vibration response.

View full abstract

The previous studies, referring to improving the ride comfort of railway vehicles related to the carbodies' vertical bending vibration, generally focus on reducing so-called "first bending mode" of the carbody. However, not only the first bending mode of the carbodies, but the vibration with their shear deformation (i.e. the vertical section of the carbody becomes a rhombus shape) often affects the ride comfort of passengers. In this study, the authors have proposed "corner braces" which combine the floor/roof structures with the side structure to constrain the deformation of the section of the carbody. Excitation tests on the rolling stock test plant have been carried out for two types of test vehicles with stainless steel carbodies, one of which is carbody frame alone and the other is the complete vehicle with the same condition as the commercial commuter type vehicles. The effect on the carbody made of the aluminum alloy, have also been investigated by the normal mode analysis with the finite element model (FEM). The results of the excitation tests or the numerical analysis have shown that the proposed corner braces successfully improve the rigidity of the carbodies and the natural frequencies of the carbody have risen.

View full abstract

Demand of a small fan has been increasing with the flow of miniaturization of electronic devices. Piezoelectric fan is one of the fan that has been proposed. A piezoelectric fan is a flexible cantilever beam whose vibration is actuated by means of a piezoelectric material. Such fans have been employed for the enhancement of heat transfer by increasing the fluid circulation in regions. However disadvantage of this fan is low pressurization. This paper provides a thin profile fan that using the generation principle of travelling space between two reasonantly-driven plates. This theory has been achieved with both ends fixed string. This equipment is a simple mechanism that consists of only two plates, and it has an advantage of thin to the direction of ventilation. And it has advantage of low cost, because the mechanism is simple. The primary focus of this paper is to verify the air flow of our proposed fan.

View full abstract

Bolted joints are widely used to assemble plate structures and a proportion of the system damping is provided by the joints. Although the damping characteristics in a bolted plate structure are different from mode to mode, the difference of damping mechanism between the modes is not clear. In this paper, we investigate the damping mechanism for the modes of the 1st and higher of bolted plates which partially overlap. We use finite element analysis (FEA) to obtain the mode shapes form a linear FE model and the contact information such as contact pressure, contact area and sliding distance at the contact surface from a nonlinear FE model. First, we evaluate the difference in the damping ratio of the modes based on the mode shapes. Second, we evaluate the damping mechanism based on the frictional dissipation energy estimated from the contact information. The validity of the estimation procedure is shown by comparing the estimated and measured modal damping ratios form a test structure consisting of three plates bolted.

View full abstract

Spot welds are widely used to join plate structures such as an automotive and the vibration characteristics of the whole structure are highly affected by the spot welded joints. For real spot welded structures, the real spot weld locations are different from those in design drawings. In this paper, we investigate the effect of spot weld location variability on vibration characteristics of plate structures based on Fuzzy finite element method. As an interval analysis in the Fuzzy finite element method, Monte Carlo simulation is used. From the membership functions and the histogram of the natural frequencies, we discuss the effect of spot weld location variability on vibration characteristics. As an example structure, the structure that consists of hat section steel plates joined together by 20 spot welds at the flanges is used.

View full abstract

The demand of the glass for FPD is increasing. Therefore, development of new cutting technology with higher manufacturing efficiency is desired. Usually, there are two processes in cutting the FPD glass. The first process is to scribe on the glass by laser or wheel cutter. Next process is to cut the glass along the scribe line by bending stress. In this process, the glass is cut using the way that run along the scribe line while pressing by the roller. In the next step, the same process is repeated after the glass rotated 90 degrees. If this process of rotation can eliminate, it would be possible to shorten the processing time. Therefore, using the tensile stress generated by the loop of the vibration mode, we thought that glass could cut the cross at once. It was found the possible that the glass can cut a cross used a vibration mode from the results of FEM analysis and an experiment.

View full abstract

Many methods have been proposed for the unknown disturbance estimation. However, these methods are mainly for minimum phase systems but a few methods can be applied to non-minimum phase systems. Moreover, it is difficult to improve unknown disturbance estimation performances because of the phase lags of non-minimum phase systems. In the present paper, a new design procedure of an unknown disturbance observer by using a parallel feedforward mode is proposed and the effectiveness of the proposed method is verified by numerical simulations.

View full abstract

This paper considers the active vibration control of a distributed-parameter planar structure. Difficulty in actively controlling a distributed-parameter structure attributes to an infinite number of vibration modes it has, causing spillover problems that lead to the instability of a control system. First, a background of smart cluster sensor based upon the distributed sensor is outlined. Then, by assuming the reciprocity between sensing and actuation of a structure, the shaping function of the piezoelectric ceramics actuator is introduced. When the shaping function represented in a quadratic form is applied, the control force shall not be null regardless of the nodal lines running even on the actuator. One of the necessary conditions for the actuator to avoid the control spillover problem is that a control force cannot become zero, when the nodal line runs over the actuator. Finally, the experiment using a simply supported rectangular panel is conducted, demonstrating the validity of the proposed piezoelectric ceramics actuator.

View full abstract

In this study we investigate cylindrical dynamic damper to reduce electro-magnetic vibration of electric rotating machinery as turbine generator. In a turbine generator, the rotating electro-magnetic pull force of the rotor causes the stator core vibration of the oval deformation rotating synchronously with the rotation speed of the rotor. Connecting a cylindrical dynamic damper to the stator core by 8 radial springs and optimizing the stiffness of the connection springs, the responses of the oval natural modes excited by the electro-magnet pull force of the generator rotor can be reduced. We calculate the dynamic response of the core in a case of applying a cylindrical damper to a 300MW class turbine generator numerically. According to the analysis results the transmission of the electro-magnetic vibration to the base of the generator from the stator core can be efficiently reduced by the cylindrical damper. The cylindrical dynamic damper is very suitable to install in the turbine generator.

View full abstract

High automotive hydrocarbon emission during cold start is a well recognized challenge with increasing importance in moving towards green vehicles. In this study, the applications of the linear model reduction techniques for nonlinear systems are discussed. A reduced order cold start model of an SI engine and after-treatment system is realized using a balanced truncation technique. A nonlinear physical model and the reduced order model are simulated in an open-loop system. The comparison results indicates the balanced truncated model performs good enough since it is reduced without losing its nonlinearities by the similar-transformation which is realized around the operation point used for the linearization.

View full abstract

Variable flux-path magnetic suspension using flux concentration is studied analytically. It was shown that flux-concentration type can produce larger suspension force than the conventional variable flux-path system using ferromagnetic control plate. However, it was difficult to achieve stable suspension since the control (variable) force was not so large. In this paper, to solve such a problem, the characteristics of the suspension system are studied by finite element analysis. In particular, the effects of the direction of motion, the operating positions and the shape of the control plates are investigated. In addition, an experimental apparatus with a variable flux-path unit using flux concentration is developed. A single-axis stable suspension is achieved by applying PD control in the developed apparatus.

View full abstract

This paper describes non-contact manipulation mechanism of multi-DOF (degrees of freedom) magnetically suspended system. This manipulation system uses unique suspension mechanism whose suspension force is controlled by air gap length. This mechanism is composed of permanent magnets and linear actuators. We study the stability of a 2 DOF suspension system which manipulate the object in the vertical plane. To analyze the stability of the system, we assume that the attractive force acts on the direction from the magnet tip to the center of the object, and is inversely proportional to the square of the air gap length. In this paper, the principle of the suspension mechanism is explained and a prototype 2 DOF system is introduced. We make a linearized model of the system and the feedback gains are calculated by linear control theory. Numerical simulations on the nonlinear 2 DOF system are carried out. In experimental system, the magnetic field analysis is investigated on the system by an integral element method and the characteristics of the system are studied. Non-contact suspension is examined experimentally. Numerical and experimental results support the feasibility of the multi-DOF non-contact manipulation system.

View full abstract

This paper discusses the feasibility of zero-power control in voltage-controlled parallel magnetic suspension systems. Parallel magnetic suspension systems are classified into two types based on the connection of the multiple coils: series connection and parallel connection. To achieve zero-power control, the integral of current is fed back in the former type whereas the integral of voltage is fed back in the latter. It is proved that each parallel magnetic suspension system incorporating the zero-power controller can assign the poles arbitrarily when the original system is controllable. It is also shown analytically that the current converges to zero in the steady state even when stepwise disturbances act on the floators in both designed systems.

View full abstract

In this paper, we present an extension of the recursive Newton-Euler algorithm, the unit vector method and the O(N) forward dynamics algorithm of rigid manipulators to flexible manipulators. Firstly, the floating frame of reference formulation is rewritten based on the relative coordinates and a recursive formula for external forces is derived to formulate the recursive Newton-Euler algorithm for flexible manipulators. Secondly, by using the extended recursive Newton-Euler algorithm as a component, the unit vector method for flexible manipulators is proposed. Thirdly, an O(N) forward dynamics algorithm of flexible manipulators is derived. Finally, some simulation results are shown to demonstrate the effectiveness of the proposed recursive inverse and forward dynamics algorithms.

View full abstract

Absolute Nodal Coordinate Formulation (ANCF) is a kind of finite element method for the flexible multibody system with large deformation and large rotation. There are few studies which extract controllers from the mathematical expressions derived by ANCF. The main aim of this study is to propose a controller design procedure by the use of the mathematical expression which is derived by ANCF. A flexible beam is introduced as a controlled object and the control torque is applied to one end of the beam. Control objective is to rotate the beam to the desired position as well as to suppress the residual vibration of the beam. In the proposed method, ANCF model employed in this paper is derived by the use of continuum mechanics approach. Some assumptions and manipulations of the derived ANCF model yields a suitable expression for controller design of μ-synthesis framework. Furthermore, dimension reduction method for the proposed controller procedure is proposed by the use of Component Mode Synthesis. The validity of the proposed method is demonstrated by numerical simulations.

View full abstract

In braking situations, excessive braking torque inputs can cause large pitching motions of a motorcycle, and it may result rear wheel lifting problems. In this paper, riding experiments are conducted on rapid deceleration conditions, and the motion of the motorcycle is analyzed based on the experimental results. The rear suspension mechanism of the test vehicle is modeled and included in a thirteen-degrees-of-freedom rider-motorcycle model, and parameter identification of the rider-motorcycle model is performed. By carrying out simulations, and using the measured brake oil pressure data to braking torque inputs, it is demonstrated that the simulation results are consistent with the experimental results, even if the rear wheel lifting is caused by excessive braking torque inputs.

View full abstract

An inverted pendulum vehicle controlled by the movement of the driver's center of gravity, such as Winglet or Segway are one of the Personal Mobility Vehicles (PMV). PMV is sometimes expected to be used in pedestrian spaces. When a driver makes a sudden operation, the driver has the potential to lose his balance according to the characteristics of the vehicle control. Because the vehicle control cannot follow the movement of the driver. Therefore, we aim to achieve the vehicle control that is friendly to the driver. As the basic study, we investigated the relationships between the behavior of a driver and an inverted pendulum vehicle at the time of acceleration in the case that handle and the hand are not constrained. In this study, we construct a model which constrains the hand and the handle, and simulate at the time of acceleration. The coupling model of the vehicle and human is built using Multibody Dynamics. The vehicle is expressed by 3 rigid bodies (tire, body and handle) and a human is expressed by 8 rigid bodies (foot, lower leg, femoral, body, head, upper arm, lower arm, and hand). We give acceleration control commands to the driver model. By the numerical simulation, we investigate the behavior of the center of gravity of a driver and the velocity of the vehicle. In addition, we investigate difference in behavior with or without constrained handle and hand at the time of acceleration operation. As the result, it was found that the case with the constraint between the handle and hand can be accelerated more quickly than the case without the constraint.

View full abstract

Timing belt is widely used in mechanical systems. It transmits rotation from driving pulley to driven pulley. Belt looks like a simple object but it is composed by belt surface, rubber, and core. And, its characteristic is not so simple. For example, it is stiff for tension and is soft for bending. Also, meshing between belt teeth and pulley teeth excites vibration of belt. To simulate such behavior of belt, Finite Element Analysis software has been used. It is true it is possible to model it precisely but it is not easy to model it and simulate its dynamic behavior. To evaluate transient behavior of belt, long simulation, for example 60 seconds, is required. For this purpose, simplified approach is preferable and multibody dynamics software with flexible body capability is a useful tool for it. In this paper, an approach to combine Beam element of FEM and rigid body with precise teeth geometry is employed.

View full abstract

In this investigation, a numerical procedure for modeling nonlinear joint constraints for the B-spline plate element is developed for the large deformation analysis of multibody systems. A concept of intermediate reference coordinates proposed for the absolute nodal coordinate formulation is generalized for B-spline elements such that a wide variety of nonlinear joint constraints can be modeled using existing joint constraint libraries implemented in existing multibody dynamics codes. Several numerical examples are presented in order to demonstrate the use of numerical procedure developed in this investigation.

View full abstract

This paper describes the formulation of the two-dimensional Euler-Bernoulli beam in the absolute nodal coordinate formulation (ANCF) by using the canonical theory. The elastic force in the ANCF has the complicated expression when the element coordinate system is introduced to derive the strain energy. In this paper, we introduce the different coordinates to express the kinetic and the strain energies. In particular, the kinetic energy is expressed by the absolute nodal coordinates. On the other hand, the element coordinates are introduced to derive the strain energy with Cauchy and Green-Lagrange strain models. The problems caused by introducing the different coordinate systems at once are solved by the canonical theory with the Poisson's bracket formalism. As a result, it is found that the strain energy of this system can be expressed as the simpler forms than the conventional formulation. The calculation results of the dynamic behavior are completely agree with the previous study. Moreover, the calculation times are significantly decreased by this formulation.

View full abstract

The paper presents a modeling method of flexible multibody dynamics in the context of implicit Lagrangian systems. The main idea is based on a Diakoptical method originally developed by Kron, which reticulates required kinematical and dynamical relations into separate ones and then incorporate them into an interconnection of implicit Lagrangian systems. By using the idea, we first show how a flexible beam attached to a rigid base undergoing a large overall motion can be modeled as an interconnected implicit Lagrangian system, in which geometrically nonlinear couplings between flexible deformations and large overall motions are incorporated into a nonlinear finite element model. Lastly, some numerical results are shown in comparison with the model developed by Simo and Vu-Quoc.

View full abstract

The governing equations for multibody systems are, in general, formulated in the form of differential algebraic equations (DAEs) involving the Lagrange multipliers. It is desirable for efficient and accurate analysis to eliminate the Lagrange multipliers and dependent variables. As a method to solve the DAEs by eliminating the Lagrange multipliers, there is a method called the null space method. In a previous report, the author presented a method which extends the null space method and reduced the order to the degree of freedom of the system. However, the presented method is for a system with constraints not depending on time explicitly. In this report, a method applicable to a system with constraints depending on time explicitly is presented. Finally, the presented method is applied to four-bar linkages.

View full abstract

Various semi-active control methods have been proposed for vibration control of civil structures. In contrast to active vibration control systems, all semi-active control systems are essentially asymptotically stable because of the stability of the structural systems (with structural damping) themselves and the energy dissipating nature of the semi-active control law. In this study, by utilizing the above property on the stability of semi-active control systems, a reduced-order structural model and a semi-active control law are simultaneously obtained so that the performance of the resulting semi-active control system becomes good. A two degree of freedom active control law is adopted as the targeted semi-active control in the present study. Optimal design parameters are obtained with Genetic Algorithm (GA). Simulation results show the effectiveness of the proposed approach.

View full abstract

This paper deals with dynamic responses of a finger protected by absorbers under impact forces. Restoring forces of a finger and absorbers are measured using Levitation Mass Method proposed by Fujii. In this paper, we carry out numerical analysis of dynamic responses for the finger protected by the absorbers under same conditions with the experiment using LMM. The absorbers and the finger are modeled using nonlinear concentrated springs with nonlinear hysteresis. This nonlinear spring is connected to the levitated block, which is modeled by three-dimensional finite elements. The experimental data are compared with the calculated ones using our proposed FEM.

View full abstract

This paper deals with nonlinear transient vibration analysis using finite element method for boxy structures made by six rectangular elastic plates supported by nonlinear springs. The bottom panel in the boxy structure is stiffened by beads. On the bottom plate, a viscoelastic damping material is laminated. The bottom plate is supported by four nonlinear concentrated springs near the four corners of this plate. The shape of the other five elastic plates is flat rectangle. The restoring force of the springs has cubic nonlinear terms and linear hysteresis damping. Finite elements for the nonlinear springs are expressed and are connected to the boxy structure modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. Comparing shares of strain energy of the elastic plates, the damping layer and the springs, we investigate the influences of the bottom panel with/without the beads on modal loss factor. Furthermore, we evaluate the influences of the damping couplings on nonlinear transient responses by the differences of the bottom plate in the boxy structure.

View full abstract

This paper describes the dynamic characteristics based on microtremor measurement data concerning a middle rise steel building. The object building which was completed in March 2004 is 44 m height and rectangular plan. Microtremor measurement is periodically continued in the building. The acceleration of measurement data in two horizontal directions and torsional direction are analyzed for natural frequencies and damping ratios on 1st mode to 3rd mode. The changes along passages and the dispersions of those dynamic characteristics in microtremor are studied. And the relations between vibration amplitude and damping ratios in free vibration waves employing manpower excitation, large vibration waves in strong wind and severe vibration waves during earthquakes are discussed.

View full abstract

It is important to grasp damping ratio on earthquake resistant design and wind resistant design. This paper describes the dynamic characteristics concerning a super high rise reinforced concrete stack based on vibration measurement data. The object stack is 100m height. Vibration measurement is performed twice. The first mode damping ratio in the state of construction of external structure and installation of internal ducts for smoke exhaustion are calculated. The relations between the first mode damping ratios and the state of structure are considered. Moreover, the first mode damping ratios in microtremor and in free vibration waves employing man power excitation are calculated. The relations between the first mode damping ratios and the amplitude are considered. In conclusion, the evaluated damping ratios are less than 1.0%. The damping ratio increased 30% as the amplitude increases 100 times than that in microtremor.

View full abstract

A design method of a dynamic damper by using the substructure synthesis is presented in this paper. For the purpose to reduce vibration of a stator in an electrical rotating machinery caused by the electro-magnetic fields, we adopted a method to predict effects of the dynamic damper from synthesizing the mathematical frequency response function of the dynamic damper and the experimental frequency response functions obtained from actual structure. And we derived the equations for the design of a dynamic damper's mass and stiffness by the experimental frequency response function of the structure, and we confirmed that this method has practical accuracy through an experimental evaluation on a cylindrical structure.

View full abstract

Passengers boarding on a railway vehicle are usually treated as additional mass in designing carbody and natural frequencies of carbody flexural vibrations are considered to decrease as the number of passenger increases. However, some previous studies indicate that on-board passengers behave not as additional mass but as damping. This report examines the damping effect by passengers using actual railway vehicles and compares the measurement results to the cases that iron blocks or water tanks are loaded. A stationary excitation test in the rolling stock testing plant for a commuter-type vehicle and a running test on a commercial line for a Shinkansen-train were conducted. From both measurement tests, relatively large vibration reduction effects upon different natural modes and little change of their natural frequencies were observed when passengers were boarding. On the other hand, natural frequencies were decreased when iron blocks or water tanks were loaded. The authors also tried to develop a numerical model to express the flexural vibration of carbody with passengers. It was found that a simple 1DOF mass-spring-damper system with low natural frequency and high damping ratio can simulate the passenger well. A new and valuable damping device against carbody flexural vibrations can be realized if we can simulate or mimic the effect of passengers correctly. Some basic directions or policies to develop such damping devices were discussed finally.

View full abstract

The 2011 Great East Japan earthquake caused many geotechnical damages such as liquefaction, failure of banks for housing lots and settlement of river dikes. Of them liquefaction occurred at many sites in Tohoku and Kanto districts. About 27,000 timber houses, a lot of buried sewage pipes and roads were damaged due to liquefaction. The very long duration of the main shock and an aftershock 29 minutes later probably induced the severe liquefaction and associated damage. Sidewalks and alleys buckled at several sites, probably due to a kind of sloshing of liquefied ground. Many houses settled notably and tilted. Sewage pipes meandered or were broken, their joints were extruded from the ground, and many manholes were sheared horizontally. In reclaimed land along Pacific Ocean, many facilities were damaged as well as Tokyo Bay area due to liquefaction. In an industry facility, oil fences tilted and machinery rooms sunk.

View full abstract

The main task of product development is to develop a good product at lower cost and to bring it to market in a shorter period. Conventional computer-aided design and computer-aided engineering (CAD/CAE) systems are well established in this regard. However, although upstream design is particularly important in product development to add value and incorporate the required functions, it is difficult to apply conventional shape-based CAD/CAE systems to the upstream design stage due to the lack of design information at that stage. As a solution to this issue, we are promoting the development of a design framework called "1DCAE," which can be applied to the early design stage of product development including the conceptual and functional design phases. 1DCAE is defined as the design concepts, methods, and tools that cover the early design stage. The output of 1DCAE is input as the design requirements to a conventional CAD/CAE system, which transforms the design requirements into an actual product image. The CAD/CAE results are then fed back to 1DCAE to verify the overall functions. The 1DCAE concept is expected to realize design innovation and more innovative products. On the other hand, the product development strongly depends on the ability of engineers. Therefore we need the design education aiming for product development and human resource development to realize the 1DACAE concept.

View full abstract

Over the years, there is increasing demand for development of technologies to achieve CO2 emissions and fuel economy regulations in automobile industries. There are two types of automatic transmission, Step AT and CVT, and many manufacturers are utilizing CVT in order to improve fuel economy and drivability both. Improvement of fuel economy can be achieved by driving engine on optimal operating line, due to CVT's continuously variable ratio. Increasing demand for better fuel economy and smoother shift quality leads to increment of required functions, processes and verifications. On the other hand, project terms are getting shorter and shorter. It is necessary to find proper system configuration at early design stage. In this stage, the design should be made without 3D geometrical data. 1D-CAE is considered one of the most promising solutions to be used. It is a simulation methodology which calculates system behavior using one directional lumped-parameter system models. AMESim and MATLAB are examples of modeling and simulation tool of 1D-CAE model. This paper introduces seamless development concept, specific example and possibility of CVT system development using 1D-CAE plant model. In addition, to consider the effect of education for engineers in the enterprise using the 1D-CAE model.

View full abstract

This paper deals with one example of education method for Engineering Design (ED) using 3D CAD and CAM. In our course, ED education classes are performed in several years. One of the class "Mechanical science design method" has an aim to design a propeller buggy car. There are aims that are Group working, Digital engineering, Digital manufacturing and presentation. 3D CAD and CAM are helpful devices to understand ED process. It is found that there are some problems of education effect for this class.

View full abstract

This report is described a summary of CAE education in Dept. of Manufacturing. One of the main CAE subject "CAE and basic exercises" is based on lecture and theoretical calculation by MS-EXCEL. Another "CAE and applied exercises" is based on lecture and practical calculation by using some CAE software.

View full abstract

The educational aspect on dynamics of machines and components has been an important part in the process of training mechanical engineers. Many authors have therefore written textbooks on dynamics and related fields by making use of their experiences. Such expertise is based on their experience, and contents of their textbooks were not clarified quantitatively in the past due to the lack of methodology in analyzing the texts. In recent years, however, some theoretical methods are proposed to quantify text data in such fields. One of the methods is ISM (Interpretive Structural Method), where structure of ambiguous system is well visualized. The other one is a text mining that is one of applications of data mining methods. The text mining attempts to obtain information from text, which is derived by devising patterns and trends through means such as statistical pattern learning. Text mining usually involves the process of structuring the input text within the data. Discussions are made to study feasibilities of using these methods in dynamics engineering education.

View full abstract

This research presents an analytical study of development of three-dimensional vehicle model to be able to examine the consumption energy of vehicle motion by functional modeling method. The three dimensional vehicle model was constructed by applying functional model, this paper by using functional modeling method, was constructed model of the damper and the viscous damping of the suspension, the calculation of the energy consumption due to frictional force between the spring and damper suspension is possible. Shows the validity of the model vehicle vibration, and transient response was verified in the road surface plane. Running a flat road surface was created based on the data measured on the highway road surface, to calculate the energy consumption of the suspension. I was able to confirm that the change in the rate varies depending on the transient response, the amount of energy consumption of 40km per hour we are, 60km per hour and 80km per hour.

View full abstract