The formation of a force field in the living body can be useful for medical treatments. For example, when we apply mechanical stimuli to cultured osteoblasts at a low frequency such as 12.5 Hz, the cell proliferation becomes promoted. On the basis of the evidence, mechanical stimuli are expected to promote the healing of fracture. Acoustic holography is a technique of forming an arbitrary-shaped force field in a space by the phase control of waves from each ultrasound transducer. Acoustic holography can be used as a means of forming a force field noninvasively in the living body. In this study, we designed a force field control device by acoustic holography. We determined requirements of the device first to design it. They are that it can control phases of waves from each ultrasound transducer, can change the intensity of force fields at a low frequency, and has more outputs that can levitate objects. Then we chose the hardware to meet the requirements and then produced the device experimentally. Moreover, we focused ultrasound and then applied amplitude modulation at 12.5 Hz. As a result, we realized the diameter of the focal point which was as big as a theoretical one and its output was large enough to affect the living body. Furthermore, we checked we can get sound pressure experimentally which obtains a component of 12.5 Hz in a space where the ultrasound transducer array forms a force field.

It has been reported that cells show adaptive response by sensing mechanical vibration. The mechanism of it is not clear but this phenomenon can be applied to regenerative medicines of articular cartilages. In this study, chondrocytes from porcine articular cartilages were cultured without scaffolds. Control groups and vibration groups were prepared for comparison and they were incubated for 20 days in order to make cell sheets of chondrocytes. The condition of mechanical vibration was sinusoidal wave of 12.5 Hz and 0.5 G. To observe the effect on production of cartilage matrices and cell proliferation, immunohistochemical examination with staining proteoglycan was conducted and the numbers of cells were measured in order to control groups and vibration groups be compared. As a result, thickness of chondrocyte cell sheets was increased by mechanical vibration at 12.5 Hz and 0.5 G, but significant difference was not shown. From the result of measurement of the number of cells, there were no significant differences between control groups and vibration groups.

Although a large amount of data (especially in abnormal conditions) is necessary to predict deterioration of nuclear power plant equipment, it is quite difficult to obtain it. For this reason, simulation is expected to be an effective approach to estimate conditions of equipment instead of data acquisition. In this study, we focused on and built a model for a motor operated valve, since the inspection cost is generally expensive due to the number of the valves used in a nuclear power plant. We analyzed the transient of stem thrust in normal and abnormal conditions. Our analytical result successfully reproduced the difference in the stem thrust; if the fluid pressure becomes excessively higher than in normal condition, the stem thrust becomes larger during valve opening.

We are developing condition monitoring methods aiming at preventing malfunctions of traction motor bearings during operation and extending the maintenance cycle. In order to verify an abnormality detection method combining vibration octave band analysis and machine learning, a rotation test was carried out by incorporating an artificial defect bearing in a traction motor. As a result, it was shown that abnormality was detected in high frequency vibration of 1 kHz or more. It was also shown that an abnormality of the output side bearing was detected by a vibration sensor attached to the counter output side.

To avoid discontinuation during long-term continuous operation in plants, a reliable monitoring system for the state diagnosis is strongly expected. However, occurring troubles of various facilities in a plant aren't simple. We proposed a sophisticated estimation method to diagnose the state for reciprocating compressors. Our monitoring system uses both the measuring data in the factory and the analytical results based on the mathematical model, which can express the dynamic behavior about the reciprocating compressor. The mathematical model has multi degrees of freedom and the model parameters are identified to estimate the state change. To realize the reliable monitoring, we have to establish estimation and diagnosis method for any change of the operation state. In this paper, we discuss estimation method of the rigidity in connecting and sliding portions by using the measuring data during operation of the reciprocating compressor when a connecting parts was worn. Using a small experimental equipment reflected the same feature of the actual compressor, we measured acceleration responses in operation and determined some natural frequencies before and after a connecting parts was changed. We identified parameters of spring constant, by which one can be obtained the frequencies of eigenvalue analysis correspond to some natural frequencies determined based on an optimal problem. Moreover, we analyzed acceleration and frequency responses of the model using the identified parameters and compared the acceleration and frequency responses of the model with those of experimental results. As a result, we found some difficulty in estimating the difference between both the cases using the estimation method of eigenvalue analysis.

A ball mill is a type of grinding equipment in the mineral and chemical processing industry. Many balls called media are put into a mill with material to be ground, and the mill is rotated. Material is ground by collision force due to contact between the material and the balls or mill wall. During operation, the collision force cause high level of vibration and sound. The vibration and sound of mills provide information related to inside of the mill and are useful for operation control. If the relationship between the internal status and the measured vibration and sound signals is clarified, we are able to estimate the internal status of material. In this study, a ball mill for experiment is manufactured and experiments are performed. On the other hand, the motion of the balls and material to be ground in the mill is simulated by discrete element method in order to predict vibration and radiated sound of the mill wall. As results, the peek values of frequency response of vibration and sound pressure is increased when the rotation speed of the mill is increased. The peek values of frequency response of its decrease when particle size of material become smaller. Moreover, the analysis results of ball motion, vibration and sound show good agreement with experimental results. The analysis result shows that the difference of the material size influences the kinematic energy of the balls. Also, there is no great difference of the frequency response when change of the kinematic energy of the balls is not large.

Hammering test using the inspection hammer is most commonly used to evaluate the defects of concrete structures because it is relatively simple. This method depends on the subjective sense of inspectors to detect defective parts. In this study, we adopt a hammering method using the rotary hammering device to improve inspection efficiency. We move the rotary hammering device along the concrete surface and measure the impact sound near the surface with the microphone attached to the device. The sound characteristics measured from healthy parts and defective parts for four types of defective depth are compared in the time and frequency domain. The time waveforms indicate the sound pressures for the defective parts are apparently higher than those for the healthy parts when the pressing force applied to the rotary hammering device is appropriate. The frequency spectrum indicate the peak frequency of the sound pressure increases and its amplitude decreases with the defective depth.

We investigated the method of detecting a void in the concrete structure by the impact test. The shock waves generated by hitting the concrete propagates along a surface and through the inside of a concrete. Sensors placed on several locations apart from the impact point measure both a surface wave and a wave passing through internal concrete. We separated a internal wave from a surface wave by the method of the independent component analysis to detect a void.

At first, we checked the effectiveness of the method by simulation. Then we made a test system. Our system was composed of a impact part and sensor parts. At a impact part, a steel ball was shot by a spring to a concrete surface. At sensor parts, a small block attached an acceleration sensor was pressed to a concrete surface by a heavy mass. By this way, high frequency components of a shock wave were measured. At last, our test equipment showed a good performance to detect a void in a concrete structure.

This paper concerns detection sensitivity of contact-type failure based on nonlinear wave modulation. Failure which has contact interfaces (contact-type failure), such as fatigue crack, delamination of composite material and bolt loosening, is difficult to detect by ultrasonic test because ultrasonic wave do not reflect at the contact interfaces. In the structure is excited by low-frequency vibration such as environmental disturbance, the contact condition of interfaces is fluctuated. In this condition fluctuation, the high-frequency wave which propagates through the failure may undergo amplitude and phase modulation at the failure location because the transmissivity and reflectivity of high-frequency waves in the vicinity of the failure may fluctuates. The degrees of amplitude and phase modulation may variates depending on the fluctuation of contact interfaces. So, low-frequency vibration which fluctuates contact condition is one of important parameters to detect contact-type failure based on nonlinear wave modulation. In this study, the sensitivity variation due to low-frequency is investigated by the experiment using the uniform beam specimen which both ends fixed and simulated failure. At first, it is confirmed linear relationship between the modulation degree and the amplitude of low frequency. Furthermore, the effect of the positional relation of failure location and natural vibration mode on the modulation degree.

It is essential for machinery to precisely measure the contact surface pressure between the parts in order to assure the quality and improve the performance. In this research, we propose the method for estimating the contact surface pressure by using ultrasonic pulse. The contact surface pressure affect the thickness of liquid interposed between the parts, such as lubricating oil. Our proposed method indirectly estimates the contact surface pressure via measuring the thickness of the liquid. We demonstrate the effective method for measuring the thickness even when the liquid is very thin, focusing on instantaneous frequency of received ultrasonic pulse. In this paper, we estimate the preload of the roller bearing as a concrete application example. In the experimental result, the instantaneous frequency of the received pulse varied according to the preload. In the numerical simulation, the received pulse varied almost as well as the experimental on the assumption that the preload affect the liquid thickness interposed between the parts. These results indicate that our proposed method can estimate the preload of the roller bearing through measurement of the liquid thickness, and can be applied for the evaluation of surface pressure of not only roller bearings also other machinery.

It is important to evaluate fastening force of the bolt to detect bolt loosening in its early stages. This study proposes an evaluation method for fastening force of the bolt. The proposed method uses an ultrasonic pulse that transmitted through the bolt, and focuses on its instantaneous frequency. Our previous study has shown that only a vertically incident ultrasonic pulse is applicable to a titanium bolt in a block made with polymethyl methacrylate (PMMA), which is a dental implant like object. This paper reports a new technique with an obliquely incident ultrasonic pulse that is titled at 5 degrees in order to extend the application of the method. We identified the ultrasonic paths in the block and the bolt, and estimated the received pulse using a three-dimensional numerical simulation. The simulated pulse was affected by contact condition on the flank of the thread and shear deformation of the thread that come from the fastening force. The instantaneous frequency of the pulse that was virtually received at 5 mm lower than the front of the transmitter was sensitive to the flank contact condition and the thread deformation. Next, we experimentally demonstrated the technique for evaluating the fastening force of the bolt in the object. The instantaneous frequency of the pulse that was received at the suited position also varied depending on the fastening force.

This study concerns an oscillation circuit for a piezoelectric self-powered active sensor which has a functionality of vibration energy harvesting to power itself and ultrasonic excitation of the host structure. The proposed oscillation circuit in this study consists of a piezoelectric element attached to the structure, a negative resistance element called lambda diode, a lowpass filter, a bias coil, and a capacitor as a power source which is charged by the energy harvesting circuit. In this paper, the nonlinear voltage-current curve of the lambda diode was approximated by a piecewise linear function, and its nonlinear behavior was investigated by using the describing function method. The limit cycle frequency and amplitude were obtained by drawing the loci of the describing function of the lambda diode and the admittance of the remaining circuit including the piezoelectric element on the complex plane. The resultant limit cycle frequency agreed with the experimental result with high accuracy. The limit cycle amplitude had 20% error which may be caused by the approximate calculation of the describing function.

In order to achieve miniaturization and decrease in the acceleration threshold in the autoparametric excitation harvester, we developed a Manji-shaped (Buddhist cross) oscillator and proposed use of the seismic mass attached on the Manji-shaped oscillator. We developed analytic solution by simplifying the motion of equation and qualitatively discuss the important parameters in the autoparametric excitation harvester as well. This study considers the autoparametric excitation harvester, in which the harvesting cantilever is mounted on the doubly-clamped oscillator and the directions of the displacement are normal to each other. The theory indicates that the acceleration threshold can be minimized, when the eigenfrequency for the doubly-clamped oscillator is twice that of the harvesting cantilever. In addition, the increase in the displacement for the doubly-clamped oscillator and in the degree of bending of the harvesting cantilever can help induce the autoparametric excitation easier. The Manji-shaped oscillator was fabricated through photolithography, followed by the wet-etching. The Manji-shaped oscillator can significantly reduce the harvester's volume by compacting the clamp and the beam area. The overall harvester's volume including the frame is 56×56×68 mm³. Thanks to the seismic mass attached on the center of the Manji-shaped spring, the acceleration threshold, which is required to induce the autoparametric excitation, is as low as 0.12G. The output power of our piezoelectric autoparametric excitation harvester is 1.3 mW at the applied acceleration of 0.3G and the frequency of 56.2 Hz.

In this paper, we report the damping force generated from nonlinear circuit in a piezoelectric vibration energy harvester, which is drawing attention as a small power source for IoT wireless sensor module. In recent years, much work has been done on improving the output power of harvester to oparate IoT wireless sensor module. To improve the harvested energy, nonlinear circuit called SSHI was developed and showed excellent porformance. However, the early stage SSHI requires extarnal power source. Subsequently, self-powered nonlinear circuits which require no external power source was developed from the specialty of electronics. However, for a harvester with a high electromechanical coupling coefficient k, the damping force from nonlinear circuits, which enhances by the SSHI's voltage increase, is likely to reduce the harvester's displacement and thus lower the output power. In this paper, we investigated experimentally the performance for self-powered SSHI circuit and for standard circuit considering damping force generated from nonlinear circuit for a harvester with a high electromechanical coupling coefficient. It is shown experimentally that the output power of self-powered SSHI circuit is lower than that of standard circuit due to the effect of the damping force. Additionally, the result of experiment showed intriguing phenomena that is a rate of increase of the output power decreases above a specific acceleration.

In this paper, a low-frequency mechanical resonator based on diamagnetic magnetic levitation is investigated. This resonator is advantageous for the use in a vibration energy harvester because of its magnetically-sprung design without any mechanical contact. However, as a drawback, there exists a considerable damping due to the eddy current loss in the diamagnetic material because it acts as a conductor. In this study, reduction of the eddy-current loss is achieved by electrically dividing the diamagnetic plate into small pieces to suppress the eddy-current induction so that the damping ratio of the resonator becomes under 0.01. More specifically, comparison is made for a continuous diamagnetic plate, a plate divided into10 pieces in parallel with the moving direction, a plate divided into 10 pieces vertical to the moving direction, and a plate divided into 100 grid pieces. Theoretical calculation and experimental results showed that the division of the diamagnetic plate into 10 pieces vertical to the moving direction or 100 grid pieces can reduce the damping ratio under 0.01.

In this research, we propose an electromagnetic broadband vibration power generation device based on a magnetic spring resonator using a ring magnet and a cylindrical magnet composite. In proposed design, two fixed ring magnets are placed to hold a moving cylindrical magnet in the middle whose diameter is smaller than the bore of the ring magnet, guided to smoothly move along the axis direction. Also, the fixed magnet is formed by adhering two cylindrical magnets with the same poles facing each other with a soft magnetic material disc sandwiched therebetween. Since the movable magnet is composed of two cylindrical magnets facing each other with the same pole, the minimum point of the repulsive force acting between one ring magnet and the movable magnet exists at a position close to the origin as compared with the conventional type. By analyzing and experimenting it is possible to realize a compact and wideband vibration power generation device with remarkable hardening property compared with the conventional magnetic spring resonator by adopting the configuration of the magnetic spring introducing the ring magnet and cylindrical magnet composite. It also shows that it is possible to adjust resonance frequency and introduce bistability by changing the magnet position.

The purpose of this research is to develop a self-powered ultrasonic sensor device that can be embedded in a structure without power wiring or batteries. To this end, a single piezoelectric element is used in this study as an actuator, a sensor, and an energy harvester to realize a fully self-contained sensor network-based structural health monitoring system. This paper focuses on the efficiency of the piezoelectric power generation mechanism to understand how much energy is expected when the piezoelectric element attached to the surface of a plate structure deforms by the vibratory deformation of the host plate. A mathematical model of the piezoelectric element is derived based on the elementary plate theory, and the power consumption at a load resistance is evaluated. The strain energy of the piezoelectric element is also evaluated theoretically, and the efficiency of the energy harvesting is defined as the ratio of the consumed energy to the maximum strain energy in a half period. It is shown that the efficiency calculated from the proposed model with a modification coefficient is approximately 10^-5, which agrees well with the experimental result.

The necessity for the development of micro power supply technologies for mobile phones and portable electronics has increased in recent years. Methods of self power generation using the vibration loads of structures have attracted attention as the power supply technologies. In this study, we focused on lead zirconate titanate (Pb(Zr,Ti)O3, PZT) as the generating piezoelectric element. The purpose of the study is to develop a high- efficiency PZT generator element that utilizes the vibration loads in the support members of a structure. However, piezoelectric elements only generate power in the order of several microwatts, so improving their power generation capacity is of the utmost importance. In this paper, experiments of driving the accelerometer for continuously driving using the laminated PZT elements are reported. The accelerometer module device was composed of capacitor, switching circuit, voltage sensor and accelerometer module. The charges generated from the laminated PZT element are charged by the capacitor. And it reaches to the Accelerometer module through the switching circuit. As a result, it is possible to obtain the acceleration information. Based on these results, we confirmed the continuous acceleration sensor.

In this paper, we propose a new adaptive switch control method to enhance the efficiency of electrical energy harvesting using a piezoelectric transducer. In a previous research, a synchronized switch harvesting on inductor (SSHI) method was proposed. This method controls the switch device on all peaks of the vibration displacement and increases the amount of piezoelectric charge. However, the increased piezoelectric charge generates a vibration-suppression effect that reduces harvested energy when the vibration damping force of the piezoelectric transducer is not negligible. To solve the reduction problem, a switching considering vibration suppression (SCVS) method was proposed. Furthermore, an adaptive SCVS (ASCVS) that was selected the best switch control time was also proposed. ASCVS estimates and predicts the amount of piezoelectric charge. However, piezoelectric parameters can be changed by temperature, which leads a miss of the selection. The appropriate switch time exist in each harvesting system that is constituted by a vibrated structure, a piezoelectric transducer, and an electric circuit. Components of the harvesting system has diversity, as the system is expected to harvest on various vibrated environments, to generate a voltage from various piezoelectric transducers, and to supply the electrical energy to various electrical devices. Thinking of the situation of the harvesting system, modification of each parameters depending on the changing temperature is infeasible. Therefore, a model-free control method instead of ASCVS is needed. Our proposed method selects the appropriate switch control time without a counter and an observer. To realize the model-free controls, we use fuzzy expressions instead of mathematical expression. We present the efficiency in the numerical simulation. The simulation reveals that the proposed method realizes the pausing switch control and recovering vibration amplitude.

This paper investigates active vibration control effects of Dielectric Elastomer Actuator (DEA) and magnitude of exciting force generated by multi-layer DEA. DEA attracts attention as a next-generation actuator because of lightness, flexibility and deformability. Frist, the state-space modeling of the system is conducted by system identification approach with the experimental modal analysis for control system design. Second, the vibration controller is designed by solving the H_∞ control problem and, finally, the closed-loop performance is evaluated by experiment.

In our previous studies, high accurate periodic solutions of semi-active vibration control systems using piezoelectric actuators are obtained by shooting method which is a numerical method for periodic analysis of nonlinear systems. The obtained results show bifurcations of solutions and the following phenomenon is observed in many solutions after the bifurcations. In these solutions, voltage inversion processes in very short periods are often interrupted by switching operation controlled by state feedback laws. However, realistic systems have delay of sensor outputs and such interruptions may be unrealistic phenomenon. In this study, a first order delay element is introduced into a model of the semi-active control systems as a simple model of sensor delay and periodic responses of the model with the sensor delay are obtained by shooting method. The obtained responses show that interruptions of voltage inversion processes are observed in a case with small delay as well as in cases without delay, whereas interruptions of voltage inversion processes are replaced by repetitions of them in a case with large delay.

This paper describes a method to improve vibration isolation performance. The purpose of this research is to suppress the resonance without increasing the displacement transmissibility in the frequency region higher than the natural frequency of the plate-type support structure. Because it is impossible to be achieved with the viscous damping, we use hysteresis damping in this research. In this research, we use a method of amplifying the dielectric loss tangent of a piezoelectric element by using a negative capacitance circuit because the dielectric loss tangent of the piezoelectric element is categorized into the hysteresis damping. The effectiveness of the proposed method was verified through simulations and experiments.

In general, PI feedback control is used for actuation by the voice coil motor. However, if the mechanical system is subjected to disturbance, the vibration of the system is not significantly suppressed. One of vibration damping methods using a voice coil motor is electromagnetic shunt damping, which can suppress the vibration only by attaching the shunt circuit to the voice coil motor. In this paper, we propose the two-degrees-of-freedom control which simultaneously performs force control and electromagnetic shunt damping.

In order to accurately and easily measure the rotational property of a ball in flight, we attempt to use a baseball with a built-in acceleration sensor unit which consists of one three-axis sensor for Low G and three sensors for High G. Two approaches for obtaining the rotational speed and its axis of the ball from outputs of the sensors are investigated; one is based on rotational acceleration component in the outputs and the other is based on translational one. In flight experiments, we obtain the time series data of acceleration for two kinds of flight trajectory of straight and curve balls. By using these experimental data, we measure the rotational speed and rotation axis with the present two algorithms. As the results, in each algorithm it is shown that the rotational speed is decreasing with time, and also that the rotation axis keeps almost constant during the flight. These results indicate the effectiveness of the present algorithms. In particular, the latter result means the validity of our assumption on rotation axis. The estimated rotational speeds are 15.0 rps and 22.4 rps in average for straight and curve ball, and the difference between the results of the two algorithms shows 0.6 rps and 0.03 rps, respectively. On the other hand, the difference in rotation axis is approximately 19 degrees in the case of straight ball while that is 16 degrees in curve ball.

Recently, electric devices such as smart phone and wearable devices have been rapidly became widespread following the evolution of digital, technology, sensor performance and application software technology. Various sensors are mounted on those devices, including GPS, accelerometer, gyro sensor, light sensor, magnetic sensor etc. Monitoring data of daily life is easily obtained by carrying these devices. Personal usages of these devices can allow us to do an activity monitoring or a specific health issue monitoring, a fitness tracking and a gauging for alertness and energy levels. For these personal usages, it is important to classify accurately human activities using signals from sensors imbedded their electric devices and machine learning technology may be an effective technique. In the study, we carried out the activity estimation using the acceleration data obtained from smart phone. The human activities are classified into six patterns of running, walking, standing, sitting, and two types of climbing stairs. The smart phone for data collecting is attached outside of a thigh. As a result, classifier with best performance was the recognition system adopting machine learning technique of random forest and if several problems are solved, the system can improve the performance to the level causing no problem in practical use.

It is important to monitor surface condition between a rail and a wheel when evaluating running safety of a railway vehicle. This paper proposes the method to estimate coefficient of friction between the rail and the wheel in curve of various curvature from the vertical load and lateral force measured by a PQ wheelset. Yaw angle and lateral displacement are estimated by Kalman filter including two degree of freedom model of the wheelset. The relationship between the friction coefficient and creepage is obtained, which shows the saturated coefficient of friction.

In real drive measurement, Resolution is insufficient to calculate the indicated mean effective pressure (IMEP) or mass burnt fraction (MBF) from the in-cylinder pressure waveform sampled with the actual vehicle crank position pulse. Furthermore, it is difficult to mount and measure the pressure sensor on the engine in the actual vehicle. The portable combustion analysis system using The Fourier type IMEP calculation was developed to solve these it. This system can measure with a crank angle signal using a pulse wheel including missing teeth, and it also supports measurement of Spark plug washer type force sensor (PWFS). The validity of this system was confirmed by an engine bench experiment. In this experiment, cylinder pressure was measured at 6-degree intervals, IMEP equivalent to conventional combustion analyzer and MBF 50% crank angle were obtained.

Recently, traffic congestion due to increase of the number of vehicle possession and freight distribution has been become a serious social problem. In order to solve this problem, various examinations using traffic simulation systems have been carried out before now. However, the current simulation system does not have sufficient reliability and reproducibility on the traffic behavior, such as car appearances, driving lane change and running speed of cars etc., because those are defined by random numbers and arbitrary conditions. From these reasons, traffic flow measurement system needs to be developed to improve reliability of the system and reproducibility of real traffic on the simulation system. In our previous work, the mAP value of classifier using R-CNN was 61.7 and the recognition rate of identical vehicle did not reach satisfactory level. In this study, we will build a classifier with the better accuracy and implement SURF feature method to detect identical objects. Furthermore, we add a new function that objects are mapped to Google Earth to be able to identify the position and the appearance time of the vehicle at a glance. As a result, these approaches are sufficiently successful on grasping traffic condition around our own car being equipped with a drive recorder. In the future, those are necessary to examine the features that recognize objects and to reduce the image processing time.

Recently, traffic congestions caused by increase of vehicle possession and complicatedness of traffic system have induced several serious social problems. In order to solve these problems, a lot of attempts have been carried out in many areas including new type of traffic signal system employing fuzzy control or neural network system. In addition to that system, a visualized miniature traffic simulation system based on real road system has been developed to examine the performance of the new traffic signal system and its effectiveness has been proved in several problems.

However, the simulation system is insufficient with the aspect of the model's validity because behavior characteristics of real traffic systems are not sufficiently reflected in the system. In this study, a traffic flow measurement system has been developed to extract traffic flow data by analyzing images from the fixed point cameras set up over two intersections. The measurement system has been developed by optical flow and R-CNN, and its performance was evaluated based on the recognition rate of the number of cars passing the intersection and the recognition rate of matching for same vehicle and the accuracy of the means speed are also estimated by the difference of passage time at two intersections. The examination result showed that the new system has been improved in matching for same vehicles compared to the previous study.

In this study, the influence of material properties on the occurrence of subsequent collision in the direct central collision of three identical spheres was investigated by FEA (finite element analysis). A sphere with impact speed is made to collide with the two rested spheres. Based on the material properties of the A5052 (aluminum), the density, Young's modulus and yield stress were changed with half and double, respectively. The occurrence of subsequent collision was judged by the sign of the coefficient of restitution. It was found that the critical subsequent collision speed, which is the boundary of occurrence of subsequent collision, shifted to the lower speed side as the density and Young's modulus increased and, shifted to the higher speed side as the yield stress increased. That is, the subsequent collision occurs at a lower speed with higher density and Young's modulus and lower yield stress. The change of the critical subsequent collision speed due to the yield stress was the largest and, Young's modulus also showed the same degree of change, while the change due to the density was small.

The absolute nodal coordinate formulation (ANCF) is one of effective ways for describing the large rotation and deformation in multibody system analysis. A distinctive feature of the ANCF is to use absolute nodal coordinates and global slopes as the element nodal coordinates. Accordingly, it gives a constant and symmetric mass matrix. On the other hand, elastic forces, which are generally expressed by highly nonlinear terms, affects computational performance. Therefore, one of significant topics in the implementation of the ANCF is to derive mathematical descriptions of the elastic forces which can be calculated efficiently. The authors proposed an efficient calculation procedure for the ANCF beam element under the assumption of the Euler-Bernoulli beam theory. Thus, this study is aimed at extending the method to the two dimensional shear deformable ANCF beam element. In particular, we introduce the method called the elastic line approach, which can avoid the shear locking problem. In the present formulation, the strain and the kinetic energies are expressed as functions of the element and the global coordinates, respectively. Then, algebraic constraints regarding the relations between the global and the element coordinate systems are introduced by means of the Lagrange's method of undetermined multipliers. Therefore, this method can be categorized into augmented formulation techniques. The equations of motions of this constrained system are derived by the Lagrange's equation. As the result, equations of motion are given by the differential algebraic equation with index-1. After that, in order to evaluate the proposed method, it is applied to the large deformation problem in the plane case.

In this paper, we address a problem of time-optimal trajectory planning for machines and robots modeled as multibody systems which is important to increase productivity in the factory. We propose a general and efficient algorithm that can generate a near-time-optimal trajectory considering system dynamics and limits of actuator driving forces/torques. Proposed algorithm combines path parameterization technique by using B-spline, trajectory optimization algorithm along a specified path which was originally developed for motion planning of robotic manipulators and a nonlinear programming formulation. Some simulation and experimental results are given and compared to illustrate the effectiveness of the proposed method.

This paper describes study on numerical analysis method of contact behavior of particles constituting sand gravel. Conventionally, Distinct Element Method (DEM) is used for analyzing particles such as sand. However, the DEM has a problem that the time step has significant influence on result of numerical analysis since the contact force depends on the overlap between particles. In this study, Non-smooth DEM is focused on, which can solve the aforementioned problem in conventional DEM. However, in Non-smooth DEM, it is not well-established to formulate the adhesive force cause by water included in sand gravel and to identify the parameter associate with the adhesive force. In this study, a method for incorporating adhesive force in Non-smooth DEM and identify the associated parameters are proposed. Identification experiment is performed and parameters associated with adhesive force are determined. The proposed method are verified qualitatively by numerical analysis.

This paper describes behavior of the jump robot which is connected by tether. The internal environment of the hole existing on the moon is not clear and is expected to be investigated. For research of the unknown environment, exploration is planned using a rover with umbilical tether connecting a mother rover near the hole. Then, it is important to study how tether influences jumping behavior of the rover. Equation of motion and differential algebraic equation is formulated by the use of Absolute Nodal Coordinate Formulation (ANCF) and multibody dynamics. Rover is regarded as two bodies with slider joint. Telescopic motion of spring expresses effect of jump. Numerical analysis reveals the relation of jumping behavior and parameters, and is compared with experimental result.

It is not easy to control position and attitude of mechanical systems with cables or tethers, because tension and inertia of the cables become disturbances, which greatly affect the behavior of the mechanical system. However, there is not enough studies on the control of such a mechanical system with cable. In this study, the cable is expressed by absolute nodal coordinate formulation (ANCF) which is one of the nonlinear finite element methods. Control law is proposed by the use of the structure of obtained model. The proposed method controls the mechanical system so that the influence of the tether is compensated. In order to achieve the proposed control law, state variables of the cable are estimated by Kalman filter and state feedback controller is designed. Numerical analyses are carried out for evaluation of the proposed method.

In this paper, we analyze the behavior of the chain by the analytical method of the multibody dynamics. For this system, there are two problems in the conventional method. One is the description of rotation for the rigid body. It leads to high nonlinearity and singularity caused by rotation. The other is the calculation efficiency due to the degree of freedom increases. In this research, in order to solve these problems, we introduces ”Rotation update equation”, which uses an incremental rotation for describing rotation matrix. This method doesn't use the rotation angle in the equation, therefore the problems are mentioned improved. It can also reduce the calculation time, too. Moreover, this study introduces the normalization of the equation of rotation with the time step. It enables us to reduce the times of iteration procedure. This research compares the calculation results by the proroposed method with the results obtained from the experiment using the ball chain. We verified the validity of the proposed method.

Morphing wing technology is to change the wing shape during flight. The technology has a potential to improve aircraft performance dramatically. One of the attractive morphing wings is the wing that can deploy or fold in the wing span direction. Such a morphing wing is called a deployable wing. The wing consists of several wing bodies jointed by hinges. A deployment actuator and a latching system are attached to the hinge. To obtain the good design of the deployable wing, the deployment simulation using a numerical model is necessary. We have proposed the numerical model comprising flexible multibody dynamics using absolute nodal coordinate formulation (ANCF) and unsteady aerodynamics. The model expresses the coupled motion of large aeroelastic deformation and large rigid body rotation. The model has a constant mass matrix, which means that there is no need to consider imaginary forces. However, it is difficult to model the deployment torque considering relative rotation angle between bodies because ANCF uses vectors expressed in a global coordinate system as nodal variables instead of rotation angles. This paper presents a modeling method to overcome this difficulty. Additionally, we model a lathing mechanism that is necessary for the deployment simulation. Finally, parametric deployment wing simulations are conducted to show the applicability of the model.

Recently, the robots have been used widely in various fields. Along with that, opportunities to use robots by users without expertise are increasing. Recently, the robots have been used widely in various fields. Along with that, opportunities to use robots by users without expertise are increasing. Therefore, the methods for simplifying the operation of the robot are required. In a previous study, we have proposed a method that uses the dynamic model and virtual external force and torque to simplify the motion generation of multi-link robot. In the proposed method, the virtual external force or torque is used as the constraint. The dynamic motion simulation is performed, then, from the simulation result, reference motion of the real robot arm is obtained. The effectiveness of the method was confirmed through several numerical simulations, but consideration of dynamic characteristics was insufficient. There is kinetic energy and operating torque as dynamic characteristics. The kinetic energy and the operating torque depend on the joint angular acceleration of the robot. In previous proposed method, there is the problem that the other constraint conditions can not consider when operating torque is controlled since the external force is converted to torque by inverse dynamic model. In this study, we propose new motion generation method considering the dynamic characteristics by correcting the target value. In this method, when the operation torque and kinetic energy is increase, the target value time decelerates. As a result, angular acceleration decreases and kinetic energy and operating torque decrease. In this paper, we verify the effectiveness of the method by the simulation and show the result.

In recent planetary exploration, sampling of rock samples and removal of obstacles are carried out by grasping operation of the exploring robot with a manipulator. In general, objects to be grasped by the manipulator should be small so that the manipulator can stiffly grasp and precisely move the objects. Furthermore, pushing motion is also expected as a method to move heavier objects which is difficult to be lifted by manipulator. For these reason, many studies on pushing motion that allow the manipulators to move the heavier objects have been conducted. Furthermore, the manipulators have become more flexible, and their weights have been reduced to save the load capacity and cut the launch cost of the rocket. As a result, the rigidity of the manipulator decreases and the flexibility of the manipulator may affect the operation, so it is not easy to push the manipulator with a flexible manipulator (flexible link manipulator). However, studies on pushing motion by a flexible-link manipulator has not been done sufficiently. Therefore, this paper extracts the problem of pushing motion by the flexible-link manipulator and propose a trajectory strategy to move the object to the target position by pushing motion of such a manipulator. Then, the control system considering friction are designed, and numerical analyses are done for the evaluation of the proposed method.

Currently, various microgravity environments are being developed for the development of new materials and the analysis of physical phenomena. However, existing microgravity generation methods have problems such as high cost for microgravity experiment. Therefore, we have proposed a system with low cost which relaxes on restrictions an experimental site. The proposed system realizes a microgravity environment by dropping the capsule, accelerating with a ducted fan, and taking control of air resistance force into control. In this report, the proposed microgravity environment system is modeled by the use of multibody dynamics and derives the torque for stabilizing the attitude of the system. In addition, the effectiveness of the model and the control system are verified by conducting numerical analysis and verification experiment using the derived equation.

Snowboard manufactures make many prototypes in design process of snowboard. This method takes a lot of cost and time. Snowboarding simulation methods have been developed in order to solve this problem. However, few snowboarding simulation method based on the discrete dynamic behavior of snow has been developed. In this study, we develop a snowboarding simulation method using Distinct Elemental Method (DEM) to reproduce discrete behavior of snow. As a result, the simulation evaluates relationship between the turn and board shape. At the same time, we develop a test equipment to verify the validity of the simulation method. The parameters used for the simulation, which are board shape, particle mass and other parameters necessary for reproducing the running surface, are identified from the test device. As a result, the same tendency is confirmed in simulation and test.

Recently, several types of nursing care equipment to aid the lifting and transfer of aged persons have been developed. Especially, rotational boom-type care lifts are used widely because of their simplicity and usefulness. However, such lifts sometimes provide a feeling of uneasiness because during lift-up, the center of the human body moves backward relative to the position of the heel. Hence, in our previous study, we proposed a telescopic boom-type care lift to approximate the trajectory of the lift-up motion of a human standing up naturally. By using a multibody dynamics approach, we showed that the proposed mechanism can achieve nearly natural standing-up motion and requires a smaller force for lift-up than that required by the conventional-type lift. After that, we considered the optimal design of the proposed care lift structure. We proposed an algorithm to seek optimal design parameters that minimize the error between the tip trajectory of the lift and the human chest trajectory measured using a motion capture system. We developed a prototype telescopic boom-type care lift with the optimal design parameters and confirmed that it can reduce the burden on cared-for persons compared with that imposed by the previous design. In this paper, we first re-examine the standing-up motions of elderly people. As a result, it is found that the pelvis of most elderly people is inclined backward and it makes difficult to stand up. Therefore, we propose to add a back support wire into the previously proposed telescopic boom-type care lift. We approximate the cared person by a three link model and combine it with the multibody model of telescopic boom-type lift. After that, multibody dynamics analysis is performed and the effect of the back support wire is investigated.

Concerning the train set buckling phenomenon, maximum coupler force may be usually estimated by means of the numerical methods based on the low of conservation of mechanical energy or numerical integration. Though these methods has many records in the past, there has been no definitive comparison between these methods. In this paper, differences between these two methods are demonstrated. Based on the results of the study, the conception available for distinguishing the usage between the two methods is summarized as follows. First, coupler force obtained from the method based on the low of conservation of mechanical energy tends to be larger than the numerical integration method. Therefore, if the coupler force obtained by the former method does not exceed the limit value related to strength, there is no need to apply the numerical integration method. Second, when a train set contains more than one car, numerical integration method will show more precise values. Finally, the transient response of coupler force and acceleration can be obtained only by the numerical integration method.

It is important for railway vehicles to get compatibility between curving performance and running stability. Utilizing independently rotating wheels may be an effective solution. The EEF bogie proposed by Frederich in 1980th shows good curving performance making use of gravity restoring force generated by the tread gradient of independently rotating wheels. However, the bogie gives rise to a kind of hunting motion as the vehicle running speed increases. In previous research, an effective modification of the EEF bogie which solves the hunting motion is mentioned. The solution is to incline both wheel axles while adjusting tread gradient of each wheel. It has been reported that the proposed bogie can dramatically improve the hunting stability as compared to the conventional EEF bogie from the result of eigenvalue analysis. In this paper, the EEF bogie with inclined wheel-axles is analytically evaluated by MBD simulation. The proposed bogie has excellent curving performance in tight curved section as compared to the conventional bogie and IRW bogie. Furthermore, the proposed bogie has high speed stability equivalent to the result of linear stability analysis. As those results, it is possible to achieve both high speed stability and high curving performance utilizing the proposed bogie unit in the vehicle.

This paper presents the experimental results of the transient characteristics of the tangential force between small cylindrical specimens assumed as a wheel after re-profiling and a new rail respectively, generated in the case where the frictional force is applied to the wheel/rail contact surface repeatedly, and also the results of the numerical analysis of the influence of the wheel/rail contact surface properties on the running performance of the railway vehicles. In the experiments, the tangential force characteristics in case of sweep under the different longitudinal slip change rate conditions have been obtained by means of a twin-disk sliding-frictional rolling machine equipped with the environmental device in RTRI. The experimental results show that the tangential force coefficient is smaller in the range of a low longitudinal slip ratio compared with the Kalker's theoretical characteristics that are obtained by applying the Levi-Chartet's formula of saturation, which are the steady characteristics of the tangential force, in case of the contact surface close to that after re-profiling, and that the tangential force coefficient becomes large when the frictional force is applied to the wheel/rail contact surface repeatedly. This means that the coefficient of friction becomes large due to the repetition of the rolling and sliding friction. In addition, in order to investigate the relation between the contact surface properties and the running performance of the railway vehicle, a numerical analysis using a simple wheel-rail dynamic model was carried out by comparing Kalker's theoretical value with the experimental values. As a result of the numerical analysis, it's clarified that in case of the power running, the wheel after re-profiling is more slippery than that without re-profiling after long run in the range of a low longitudinal slip ratio.

The elastic vibrations of the carbody tend to have influence on riding comfort in recent railway vehicles. In particular, the modes similar to the first bending mode of free supported elastic beam (“B mode”) and diagonal distortion mode (“D mode”) are important. These vibration modes have natural frequencies around 10Hz which is known to be a sensitive frequency range for human. We proposed a method for multi-modal vibration reduction using active mass dampers (AMDs) to reduce such vibrations. As the result of the running tests on an actual truck, it was confirmed that the vibration reduction effect on B mode and D mode could be obtained. In this paper, H-infinity control theory is used for controller design in order to improve control effect. In order to use this theory, a numerical analytical model was created and a method to reduce the dimension of the model was proposed. As the next step, the controller was designed by using the reduced model, and the excitation tests by using the Shinkansen type test vehicle were performed. As the results, it was confirmed that the vibration reduction effect on B mode and D mode could be obtained. Furthermore, it was shown that the ride comforts were improved on the all measurement points on the floor in simulated running condition.

Cryopump is a vacuum apparatus used in various high-accuracy measurement systems such as those for detecting gravity wave and observing micro motion of molecules. However, the pump induces vibrations with multiple frequencies, which may deteriorate measurement accuracy. To overcome this problem, a vibration isolation apparatus with an active dynamic vibration absorber has been developed. This study focuses on removing the vibration of low frequencies because conventional vibration isolation devices for cryopump hardly remove them. A controller is designed based on the internal model principle to remove the vibration at several specified low frequencies. In the experiment, the vibrations at four specified frequencies are reduced to virtually zero with the implemented controller.

This paper deals with the control system design for active isolation table that loads a dynamical object. When elastic loads are put on the isolation table, vibration modes of the table are changed. Therefore, the controllers for the active isolation table should be designed taking account of elastic loads.

In this research, an experimental active isolation table with an elastic load is built. Its dynamical model is identified by using experimental modal analysis or FEM analysis. A controller is designed to suppress horizontal and vertical vibration simultaneously. In this study, the experiment system is designed to suppress vertical vibration. Property of the improved control system is qualified through computer simulations and control experiments.

In the present paper, we discuss control design of switching system for a pneumatic isolation table including different time delays depending on control input polarity. The control performance of the pneumatic isolation table depends on input time delay, and the input time delay is determined by response speed of valve and pipe length. Especially, when the valve response speed and the pipe length are different between the supply side and the exhaust side, the input time delay differs depending on the input polarity. Therefore, we design the control system to switch the system to the pneumatic isolation table based on the input polarity. In the present paper, a control design is discussed and the effectiveness of the proposed method is verified by numerical simulations and experiment at results.

In the present paper, we discuss servo control design for discrete valued input system. In conventional servo systems, tracking errors caused by quantized errors of control input accumulates the errors in the integrator and it lead to applying impulse type control input. The input provides undesirable vibration response. We propose a switching control law based on Lyapunov function in order to prevent undesirable response. The effectiveness of the proposed method is verified by comparing with some conventional methods through experiments.