Although the number of accidents at level crossings in Japan has been decreasing annually, there is still possibility of such accidents to occur due to wrong-way entry. Therefore, it is essential to study the crashworthiness of rail vehicles in level-crossing accidents. Given that there are many possible collision scenarios for such accidents, it is useful to perform a comprehensive analysis of these scenarios. To investigate the crushing characteristics of a double-skinned aluminum-alloy car body structure for a conventional railway line, we conducted impact compression tests. The impact condition compresses the overall specimen's end face (overall compression condition) and part of its end face (local compression condition). The results of the impact compression tests were as follows. Buckling was the main cause of failure in the overall compression condition, whereas shear crushing was the main cause of failure in the local compression condition. Finite Element Method (FEM) analysis was also conducted in which several material rupture laws were used and compared with the test results. No appropriate solution could be obtained when the equivalent plastic strain was used as a threshold, whereas the results of analyses using the ESI-Wilkins-Kamoulakos (EWK) model showed good agreement with those of the experiments in both compression conditions.
Instrumented wheelsets are widely utilized in the railway industry for the purpose of the measurement of the wheel-rail interaction force. In the conventional instrumented wheelset, the measurement accuracy of the lateral force is reduced due to the bending moment induced by the wheel load. The authors have proposed a new configuration of the instrumented wheelset to reduce the influence of the wheel load on the measurement of the lateral force. This proposed configuration utilizes the shear strains of the wheel web as a measure of the lateral force. This paper describes the accuracy verification of the proposed configuration under the wheel rotating condition. The single-wheelset roller-rig tests are carried out and the test results show that the proposed method can reduce the influence of the wheel load even under the rotating condition.
In recent years, with the depletion of fossil resources, there is a need to further improve the thermal efficiency of diesel engines. In order to improve the thermal efficiency of diesel engines, it is necessary to realize rapid combustion. The combustion process in diesel engines is greatly affected by spray characteristics and depends on air fuel mixture characteristics. Therefore, it is necessary to grasp the detailed spray characteristics in mixture formation process. In the past, many studies on the spray characteristics in mixture formation process have been reported. For example, Nishiura et al experimentally evaluated the effect of fuel injection pressure, nozzle hole diameter, and ambient density on the spray characteristics (Nishiura and Inoue ,2019). However, most of the previous reports have evaluated the spray characteristics using the total time averaged over a quasi-steady period for the physical quantity. Thus, the temporal and spatial variability of the spray and the large-scale vortical structure have not been sufficiently investigated. In this study, the turbulent intermittency phenomena in diesel sprays were investigated by using sheet scattered light imaging, focusing on the large-scale vortex structure that affects the formation mechanism of the diesel spray mixture. The intermittency of the diesel spray was investigated by applying the analysis method used for clarifying the phenomenon of turbulent intermittency in free jet flow to the analysis of the diesel spray. In this experiment, the effects of injection pressure on the intermittent behavior of the diesel spray were investigated.
It is important to enhance the safety of the railway passengers on board in the event of a collision accident. The railway vehicle standard in European countries and the U.S. set the framework for structural crashworthiness design. On the other hand, an evaluation method for the crashworthiness design of railway vehicles has not been established yet in Japan. Our objective is to suggest the safety index for the railway vehicles in which longitudinal seats are arranged. The severity of passenger’s head injury was estimated in a level crossing accident scenario, including the horizontal collision position to a dump truck, the collision angle, the vertical collision position and the load weight of the dump truck by using numerical simulation. The correlation between the severity of injury of an Anthropomorphic Test Device (ATD) model and the safety index, integral of deceleration waveforms, mean deceleration waveforms and maximum waveforms which occurs on the railway vehicles at the time of collision with a dump truck were verified. It was found that the integral of deceleration values during an integration time timp had the highest correlation with the injury values of ATD. We suggested the integral of deceleration and the critical values of the second-furthest away from the bench-end partition as an evaluation method for the crashworthiness design of railway vehicles.
Pupils give favorable impressions to humans depending on their size. Focusing on effects of the pupil size, various pupil sizes were evaluated using human images as stimulations in previous researches. However, it is difficult to express an extreme pupil size in a face image due to a limited area of eyes. In addition, the evaluation of pupil size itself is hard because impressions in human images are formed depending on not only the pupil size but also other facial parts. In order to evaluate impressions of the pupil size itself, it is desirable to extract only the pupil and exclude other facial parts. In this study, we analyzed impressions on various pupil sizes that combined the dilation / contraction using two kinds of pupil expression media that have been developed so far. In the analysis, the impression evaluation obtained by the SD method was factor-analyzed. As the result of factor analysis, three factors were extracted: acceptability, reliability, and curiosity. Acceptability and reliability factors had a certain peak, and curiosity factor was proportional to the pupil size. These analysis results demonstrated that a certain dilated area of pupil could form a favorable impression regardless of pupil expression media.
Since plants with a high biomass conversion efficiency of light energy consume less energy and require shorter cultivation periods, it is expected that plant factories can have more output with less energy. However, there have been few studies on the biomass conversion efficiency of light energy in various cultivated plants, and this agricultural engineering field is still unexplored. If the amount of energy consumed by a plant factory can be obtained from the biomass conversion efficiency of light energy, the plant types that can be grown in a plant factory and the economic efficiency of the plant factory can be clarified. In this study, we determined the amount of light energy required for plant cultivation by measuring the wavelength distribution of sunlight and plant-growing light-emitting diodes. Also, we investigated the light to biomass conversion efficiency (LBE) from the amount of heat generated by the biomass of cultivated plants. The LBE was also used to analyze the payback period of plant factories so as to estimate the profitability of various cultivated plants. However, since the market price of plants varies with the selling season, it is necessary to clarify the biomass conversion efficiency while taking into account the annual air conditioning energy consumed by plant factories. The biomass conversion efficiency by light and air conditioning energy (BELA) is the energy conversion efficiency based on the input values of light energy and air conditioning energy and the output value of the biomass calorific value of cultivated plants. In this study, a new method for economically determining the plant types that can be cultivated using BELA was proposed.
A new paper sheet feeding mechanism using a friction force owing to electrostatic adhesion is proposed to realize long-term reliability and reduction in maintenance work. In this mechanism, friction force owing to electrostatic adhesion of an electrostatic pad acts as a resistance force to make paper sheets separate successively instead of a friction force of rubber parts used in the conventional feeding mechanism. The electrostatic pad with comb-type electrodes and whose upper surface is coated with an insulator with high wear resistance generates the resistance force. First, the width of the electrode and the spacing between electrodes of the electrostatic pad that generate a large electrostatic adhesion at the lowest possible voltage are determined from an experiment using the evaluation electrostatic pad. Then, the feed force acting on the first and the second paper sheets, and the resistance force owing to the electrostatic pad are measured by pulling the paper sheets in the separation mechanism. Furthermore, the performance of the paper sheet feeding mechanism is measured while changing the value of the voltage applied to the electrostatic pad. Consequently, it was found that the paper sheets could be accurately fed successively by adjusting the applied voltage to an appropriate value.
Structural analysis of customer data such as purchase history and customer attributes is expected to be effective for designing the products that are appropriately adapted to requirements of individual customers. This paper proposes a structuralization method of customer requirements for configure-to-order products with the customer data analysis and the design structure matrix (DSM). In the method, association rule mining is applied to order reception data for extracting structural relationships among customer requirements. The extracted association rules are transformed into a customer requirements DSM, which can be used as the input to the clustering method for the multi-domain matrix across customer requirements, physical functions and entity structure. A case study of an industrial three-axis linear-type robot is demonstrated. The customer requirements DSM generated by the proposed method is compared with the one generated without using association rule mining. Its results show the effectiveness of the proposed method.
This paper presents a real-time self-attitude estimation method which utilizes the clues to the direction of the gravity hidden in images and structures of the environments. In the proposed method, the angular velocity is integrated using a gyroscope, a camera-based method estimates the gravity direction, and a LiDAR-based one also estimates the gravity direction, respectively. These estimations are integrated using the EKF (extended Kalman filter). The camera-based gravity direction estimation uses a DNN (deep neural network) which learns the regularity between the gravity direction and the landscape information. By learning the regularity, the proposed DNN can infer the gravity direction from only a single shot image. The DNN outputs the mean and variance to express uncertainty of the inference. The LiDAR-based gravity direction estimation extracts vertical planes from the surrounding environment measured by the LiDAR, and outputs the gravity direction based on their normals. By using both the camera and the LiDAR, more robust and accurate estimation can be achieved. To show the DNN can estimate the direction of gravity with uncertainty expression, static validations on test datasets are performed. Dynamic validations are also performed to show the proposed EKF-based method can estimate the attitude in real time. These validations are performed in both simulator and real world to compare the proposed method with conventional methods.
The technique of rapid evaluation of fatigue limit using infrared camera is beneficial because it not only allows the fatigue limit to be obtained in a short time and at low cost, but also it makes possible to detect the location of fatigue damage in real structures. In this technique, the fatigue limit is determined based on the temperature evolution with the load amplitude. Several data processing methods have been proposed so far to determine the fatigue limit, but no definitive method has been established yet. In this study, three data processing methods are proposed, namely, a method of selecting pixel to evaluate the temperature evolution, a method of excluding inappropriate data using adjusted R-square, and an approximation function to represent the relationship between the temperature evolution and the load amplitude. As a result, these methods are applied to experimental data and proved to be accurate and reliable enough compared to the existing methods. Experimental data were obtained for double edge notched specimens of type 304 stainless steel. The second harmonic amplitude of temperature was adopted as the characteristic value of temperature evolution for estimating the fatigue limit.
Research on shape generation using machine learning has been widely conducted, and two-dimensional laminar flow airfoils are treated as a benchmark problem. When learning airfoil shapes using variational autoencoders (VAEs), it is known that the results obtained by ordinary VAE (N-VAE) and hyperspherical VAE (S-VAE) differ significantly. The difference is attributed to the fact that the standard normal distribution is used as the prior in N-VAE and the vMF distribution is used in S-VAE, but quantitative comparison of the latent space of both has not been conducted. In this study, we quantitatively compared how the data are embedded in the latent space of both VAE models. It is shown that data with different trends are embedded near each other in N-VAE, while data with similar trends are embedded near each other in the latent space of S-VAE. The difference can be explained by the difference in KL divergence and data characteristics. The NACA airfoil data is used in the present study, and the dataset is not normally distributed, which is usually the case with other data in mechanical design. S-VAE is suitable in such a case.
The visualization system has been developed to control the fluidity of the excavated soil in the chamber of the EPB shield in real time during the shield advance. For further improvement of the visualization system, agitation tests of the fluid sand mixing with CMC aqueous solution as a thickening material or rheological form to enhance fluidity have been carried out to clarify its flow property. It was confirmed by the tests that the agitating flapper torque of the fluid sand decreased with the increase of the number of flapper rotations. It is assumed that above-mentioned phenomenon was caused by the friction in-between the sand particles. Therefore, the fluidity property of the fluid sand is not exactly same as the general viscous fluid materials. It is, however, useful to evaluate this phenomenon in a numerical formula using the power-law model for the flow property in which shear stress decreases with the increase of the shearing deformation rate, and to apply the formula to numerical analysis, if the analysis is able to simulates the fluid sand behavior with high accuracy. As a result of the agitating tests, the formulas based on power-law model applied negative value to the power index was proposed to evaluate the flow property of the fluid sand.
As a road pavement assessment tool, this paper presents an equation to estimate the vibrational ride comfort of local fixed-route buses from the international roughness index (IRI) and the bus speed. Before construction of the equation, all the needed data was collected as big data: The bus data such as acceleration, speed and position have been collected with the built-in accelerometer and GPS sensor of a smartphone for about 100 days on three national routes. After the measurement, according to ISO2631-1, the ride comfort was quantified as a running r.m.s of the frequency-weighted acceleration on a passenger seat. The IRI was measured every 10 meters with the Class 3 method. It was observed that the ride comfort was weakly correlated with the speed and moderately correlated with the IRI. For the large and the medium buses, two estimate equations were constructed in the form of a function with arguments of the bus speed and the IRI. Their parameters were determined by applying the data fitting technique to the collected big data. The estimate equations give the correlation coefficients of 0.70 to 0.79 and the root mean squared errors of 0.08 to 0.13 m/s2 between the mean values of the measured ride comfort and their estimates on the 10-meter road segments.
Magnetic flux leakage testing to compensate for the visual inspection in the inspection of the wire ropes has been studied. In recent years, it has become possible to improve the damage detection accuracy by using a device which utilizes the hall effect and magnetoresistance effect due to the development of semiconductor technology. Detection of the small damage also became possible. However, since the noise of measurement data is contained much when inspecting the wire ropes, it is difficult to detect a very small damage. Cause of noise depends on the configuration of the eccentric and the strands and the strands of the rope. Eccentricity of the rope has been demonstrated in previous studies to contribute to the noise. However, the noise due to strands and strands of the ropes is an evaluation of only the magnitude of the magnetic flux density. Thus, discussion of the direction of the magnetic flux is not performed. In this paper, the effect of noise caused by the strand is evaluated by experiment and numerical analysis. Furthermore, we verified whether useful in reducing noise due to strands of the rope by the sensor's angle. Therefore, it was found that there is due to strands of the rope as cause of noise. It showed that it is possible to noise reduction by matching the detected angle of the sensor with twist angle of the strand.
In Japan, the working-age population will roughly halve by 2060 from its peak in the late 1990s. Therefore, significant labor saving is required to maintain quality in the railway business at its current level. One such approach is the trend toward introducing vehicle monitoring devices which can automatically monitor the condition of the vehicle and facilitate efficient maintenance. However, there is no equipment for conducting a non-dismantling functional inspection on the stiffness of critical bogie rubber components subjected to forces of several kilonewtons or more, so we decided to develop such equipment. The equipment monitors the status of the bogie by using a wayside high-speed camera to measure the vibration of the bogie when it passes over iron plates approximately 5 mm thick placed on the track. This report outlines the diagnostic method, demonstrates the accuracy of vibration measurement from camera images, and presents the results of a rubber stiffness evaluation test, where axle beams with different rubber stiffness values due to the status of cracks were attached to an actual vehicle. The axle beam, which has a rubber portion at the end, supports the axle box mainly in the longitudinal direction. In addition, by creating a numerical model for quantitative evaluation and assigning a suitable stiffness value to the replacement component, we show that the model gives the same results as the test and that the longitudinal stiffness of the axle beam can be evaluated quantitatively by a wayside camera.
The performance of a table tennis racket is often stipulated using an unique standard for the manufacturer. However, the performance criteria for restitution characteristics still have been unclear due to lack of qualitative evaluation by each manufacturer. For metal baseball bats, a formula that can easily estimate the coefficient of restitution (COR) for the bat has been proposed. Similarly, it is important to establish a method that can control the COR at the design stage for table tennis rackets. In this study, first, to understand the restitution characteristics of the table tennis ball used in the official game, an impact test was conducted on a pseudo-rigid wall at low to high velocity. Then, for 15 types of rackets, the COR of the racket body (with and without rubber) was measured. Additionally, the natural frequency and flexural rigidity of the racket body without rubber were measured. Furthermore, these experimental data revealed relationships between the COR and both of the impact velocity and natural frequency of the racket. A formula for the COR was derived similar to that for a baseball bat, and developed by considering the flexural rigidity. The effect of rubber on the COR was also investigated. Consequently, the effects of ball’s impact velocity, racket’s natural frequency and racket’s flexural rigidity on the COR of the racket were clarified. From these results, an equation that can estimate and control the COR of the racket at the design stage was developed.
In this study, we propose a novel shape optimization method for designing micro- and macro-structures concurrently. We assume the macro-structure consists of several arbitrary domains, which have different periodic micro-structures. The macro-structure and the micro-structures are connected by the homogenized elastic tensors, which are calculated by applying the homogenization method to the unit cells of the micro-structures. Defining the boundary shapes of the macro-, the micro-structures and the interface shapes between the domains as design variable, the compliance of the macrostructure is minimized. The volume of the macro-structure considering the whole holes in the micro-structures is used as the constraint. The homogenization equations for the micro-structures and the equilibrium equation for the macro-structure are also used as the constraint. This design problem is formulated as a distributed-parameter optimization problem, and the shape sensitivity functions are theoretically derived. The optimum boundary and the interface shapes of the macro- and the micro-structures are determined by applying the shape sensitivity functions to the H1 gradient method. The proposed concurrent shape optimization method is applied to several numerical examples to confirm the effectiveness of the proposed method for designing the shapes of multi-scale structures. Also, the compliance and the shapes optimized are, compared and discussed for the different domains.
In this paper, we present a shape optimization method for periodic microstructures to maximize a specified vibration eigenvalue of a porous macrostructure. The homogenized elastic moduli calculated by the homogenization method are applied to the macrostructure to connect the microstructures with the macro structure. The KS function is introduced to solve the repeated eigenvalue problem hidden in vibration eigenvalue optimization. The shape optimization problem subject to the volume constraint considering the microstructures is formulated as a distributed-parameter optimization problem, and the shape gradient function is derived by the Lagrange multiplier method and the adjoint variable method. The shape gradient function is applied as a distributed force to update the design boundaries of the unit cells of the microstructures by the H1 gradient method. The smooth boundary shapes obtained by the H1 gradient method are suitable for manufacturing with a 3D printer. In the numerical examples, the eigenvalues and the optimum shapes were compared changing the number of the domains of the microstructures in the macrostructure. As a result, the effectiveness of shape optimization method for microstructures aimed at maximizing the vibration eigenvalue of a macrostructure was confirmed.
The evaluation of delayed fracture is essential owing to the widespread application of high-strength steel to reduce automotive weight. Furthermore, it is necessary to clarify the influence of local stress concentration at the notch root as delayed fracture occurs because of the accumulation of diffusible hydrogen in the stress concentration area. In this study, we used the slow strain rate technique (SSRT), constant load test, and conventional strain rate technique (CSRT) of notched specimens under cathodic hydrogen charging to obtain the tensile strength, diffusible hydrogen content, and ratio of brittle fracture surface, which consists of quasi-cleavage fracture and intergranular fracture, under various testing conditions. The results show that the relationship between the tensile strength and brittle fracture ratio of notched specimens is in good agreement with that of smooth specimens under various testing conditions. However, some data of brittle fracture ratio obtained using smooth specimens need to be modified to comply with the primary crack area. Therefore, if the primary crack can be determined, the brittle fracture ratio will be an important index for delayed fracture or hydrogen embrittlement criterion. Additionally, the relationship between tensile strength and the accumulated diffusible hydrogen content, which is estimated by FEM of notched specimens, has a good agreement with that of smooth specimens obtained by either SSRT and CSRT. However, the fracture strength curve of CSRT is higher than that of SSRT. The result indicates that the interaction between hydrogen and dislocation in the microstructure is needed to consider the influence of strain rate of the testing methods.
In recent years, as measurement devices have advanced due to sensor and information technology, we have been able to measure bat swing data just after baseball impact. Therefore, the purpose of this study was to examine the characteristics of a batter’s swing using batting skill assessments from baseball coaches with significant experience. Finally, the practicality and effectiveness of baseball coaching methods, particularly for batting, were verified through this study. The subjects were 25 male university baseball players (age: 19.8 ± 1.0 yrs, body height: 174.5 ± 5.4 cm; body weight: 72.8 ± 5.1 kg). The participants were instructed to hit the ball placed on a tee stand. Nine types of tee-batting positions (course / height) were set for each participant depending on the upper and lower limits of the strike zone according to the baseball rules. Our main findings were as follows: 1) The swing characteristics (Depth: swing time and vertical bat angle, Height: head speed, rolling angular velocity, bat radius of rotation, horizontal bat angle, and vertical bat angle, Course: rolling angular velocity) varied with respect to ball positions, 2) Through batting skill assessment by two baseball coaches with significant experience, a good batter’s swing can be characterized as high bat speed, short swing time, and high efficiency of rotational movement around the vertical axis. Additionally, the coaches suggested that for a good batter’s swing, the vertical bat angle should be stable and smaller than 9°. These results provide useful information on assessment of bat swing training methods and exercises to hit the ball to different positions. Furthermore, this study can aid baseball coaches and/or players to objectively analyze a bat swing of a player.
A mass measurement system with a relay feedback of velocity has been developed to achieve measurement without gravity. In this system, mass is estimated from the periods of oscillation in the relay-feedback system. Originally, the velocity of the object was solely fed back, which caused the orbit of the object to drift easily. A restoring force compensation by a spring was introduced to avoid such drift. However, a slight drift still occurs in spite of the restoring force element. A new estimation formula has been derived which can estimate mass regardless of the position of the closed orbit. An analytical study on this formula shows that mass is overestimated when the restoring force is neglected in the estimation. Several experimental results show that the estimated mass is slightly larger than the actual value even though the new formula is used in estimation. In the measurement, the periods of oscillation are measured with a digital oscilloscope. A delay in the period measurement is expected to cause such overestimation. To reduce the error due to delay in measuring periods, a new device for rapid period measurement is developed, which uses the edge detecting function of a micro-computer. It is experimentally demonstrated that the measurement error is reduced by the developed measurement device.
In the present study, we have addressed a suspension composed of magnetic cubic particles in a rotating magnetic field by means of quasi-two-dimensional Brownian dynamics simulations in order to investigate the dependence of the regime change on a variety of factors such as the magnetic particle-particle interaction strength, the magnetic particle-field interaction strength and the frequency of the rotating magnetic field. If the magnetic particle-particle interaction strength is relatively small, single particles remain without aggregating to form specific clusters, and the magnetic moments of single particles tend to rotate with the rotating magnetic field. If the magnetic particle-particle interaction strength is predominant, the particles aggregate to form closely-packed face-to-face structures, and the magnetic moments of constituent particles cannot follow a change in the rotating magnetic field. As the magnetic field strength is increased, closely-packed structures start to be transformed into aggregate structures with an offset face-to-face configuration. An increase in the frequency of the rotating magnetic field induces a significant regime change in the aggregate structures. Under the rotating magnetic field with low frequency, the particles aggregate to form elongated clusters with an offset face-to-face configuration along the magnetic field direction, and the cluster itself rotates to follow the change in a rotating magnetic field. From these results, we conclude that a regime change in the aggregate structure of cubic particle in a rotating magnetic field may be induced by various factors such as the magnetic particle-particle interaction strength, the magnetic particle-field interaction strength, and the frequency of the magnetic field.
This paper deals with the impact of dropped hollow rubber spheres against a planar surface. Hollow silicon rubber spheres are used as the impact source of the measurement of the floor impact sound insulation of buildings, but the impact characteristics have not been investigated. In order to clear the impact characteristics and show a strategy of a development of another type of source, we have conducted some experiments, FEM simulation on LS-DYNA and a one-dimensional mass-and-spring model analysis. The experiment of the impact of 4 types of rubber spheres, two hollow spheres with an outer radius of 90 mm and two solid spheres with a radius of 60 mm and 40 mm, against a surface plate were conducted. As the FEM solutions corresponded qualitatively with the experimental results, the impact analysis was done based on the FEM results. The FEM solution shows the shock stress propagation in a hollow sphere has two steps; the ‘first period’ is the stress propagation in a solid thickness part similar in a solid sphere and the following period is that to the hollow part of sphere. The frequency response of the impact force shows ‘notch’ frequencies correspond to the natural frequencies of the hollow sphere of free-free boundary condition. This is the key point to analyze the impact characteristics of dropped hollow spheres. We investigated the relations between durations, natural frequencies of free-free boundary condition and notch frequencies of impact in relation to the thickness ratio of hollow sphere. We have presented a simple model to estimate the duration and the peak impact of dropped hollow sphere for an actual design.
This paper considers wave analysis and control of two-dimensionally connected damped mass-spring systems, focusing on the properties of the secondary constants as an analytic function of the Laplace transform variable s. Mass motion in the longitudinal direction is considered. The system can be viewed as a cascade connection of layers comprising the lateral direction elements. The dynamics can be described by a first order recurrence formula in the Laplace transform domain. We show that the characteristic polynomial of the coefficient matrix can be decomposed into second order polynomials, which reveals analyticity of the secondary constants in the open right-half plane, as well as the separation property of the propagation constants and the positive real property of the characteristic admittances. These properties justify the harmonic analysis in the wave analysis and guarantee the closed loop stability of the impedance matching controller. Numerical examples illustrate the derived results and show effectiveness for vibration control.
For lower limb amputees, trans-femoral prostheses play an important role not only in regaining the gait ability of amputees, but also daily life activities. In recent years, the use of robotic technology has led to the development of robotic prostheses that provide better safety and comfortness in practicing normal walking. However, since daily activities other than walking rely heavily on the function of the sound leg, it is important not to put excessive burden on the sound leg in a mid-back posture and sit-to-stand motion. Therefore, in this study, in order to reduce the burden on the sound leg while using a prosthesis, we developed a new robotic prosthesis that maintains flexion posture at arbitrary knee angle in circumstances where the burden on the sound leg increases during daily life. Moreover, we proposed a model of daily activities based on finite state machine that represents not only walking, but also all daily activities such as sit-to-stand motion. Finally, we conducted experiments by a user of trans-femoral prosthesis and showed the effectiveness of maintaining flexion posture.
In logistics warehouses, Goods-to-Person systems (i.e., kitting transport systems) and workers work together in order to improve the efficiency of kitting (also called “picking”) tasks. On the other hand, in assembly factories that also require kitting tasks, Goods-to-Person systems have not yet been implemented. We propose a novel robot co-worker called Kitting Parts Delivery system (i.e., KitPaDY) to expedite work processes at assembly factories. Unlike existing Goods-to-Person systems that are designed to use a mobile robot to transfer a single shelf at a time, KitPaDY adopts a novel mechanism that enables a single mobile robot to transfer multiple shelves simultaneously. The mechanism is mounted on every shelf and does not need any power. Rather, it uses the drive of a mobile robot to group shelves together; this also simplifies the control of the mobile robot. Here, we describe the mechanism behind KitPaDY and the mobile robot’s motion. Furthermore, we conducted an experiment to gauge KitPaDY’s ability to simultaneously transport multiple shelves. Additionally, by comparing KitPaDY with existing transport systems for current kitting processes, we demonstrated our system’s efficacy in the simulations. The simulation results show that KitPaDY can reduce the required number of mobile robots by 75% compared to existing transport systems.
Ultrasonic abrasive machining is a machining method in which an ultrasonically-vibrated tool presses the workpiece via free abrasive grains and induces hammering motion of free abrasives. This machining technique is especially applicable to hard-and-brittle materials such as ceramic matrix composites and sufficient machining speed is practically achieved by performing micro-brittle fractures tens of thousands of times per second. Nevertheless, there are few studies that quantitatively evaluate the parameters of this machining method and their interactions. The problem is that this machining process is conducted manually and the machining conditions are determined by the experience of an operator. Hence, derivation of conditions to improve machining efficiency is required. In this study, the factor effects and their interactions among machining pressure, oscillator power and slurry flow, which are the typical parameters of ultrasonic abrasive machining, were evaluated by analysis of variance and the related experiments in monolithic SiC. As a result of analysis of variance and the related experiments, it was shown that the combination of machining pressure of 135 g/mm2, oscillator power of 100 W and slurry flow of 2500 mL/min remarkably improves the machining efficiency in monolithic SiC. It was also clarified that there are significant interactions between the machining pressure and the oscillator power and between the machining pressure and the slurry flow, respectively.
A single, straight-tube pulsating heat pipe (SST-PHP) with an open end that was proposed by the authors’ research group provides a high heat transport rate of 75 W with an effective thermal conductivity of 40 kW/(m・K) due to a self-excited, large amplitude, periodical oscillation of a single vapor plug. Liquid film surrounding the vapor plug is pushed back to the heating section to spread over the wick for each shrinkage of the plug, which maintains the heating section near the saturation temperature of the working liquid. In the present paper, first, the variation of the amount of liquid contained in the heating section during the oscillation is examined through the measurement of the vapor volume in the parts of the pipe. The dynamic inflow/outflow of the liquid film to/from the heating section and its relation to the occurrence of the dry-out are discussed. Secondly, the temperature variation across the liquid film that flows out along with the vapor plug into the heat transport tube is estimated with reference to the analytical solution of the temperature distribution in a liquid column oscillating with the same amplitude as that of the vapor plug. The effect of the heat transfer from the tube (temperature drop) reaches the location of the liquid film surface with a time delay around a quarter of the oscillation period. It would imply that the condensation of vapor on the film surface begins at around the maximum growth of the vapor plug, as a result, leading to the large-amplitude oscillation.
Recently in the field of design, it is becoming more important to generate innovative ideas of "what to create" at early design stage than ideas of "how well to make". Ideation informatics to enhance idea generation by adding systematicity and exhaustiveness of information technology to human intuition should be a prospective approach to the problem. In this research, a ten sentence pattern model is proposed as a computable description of function and user experience (UX) at early design stage as a fundamental technology for ideation informatics by extending the English basic five sentence patterns. An XML format is designed to add semantic information to words, phrases, and sentences described in the ten sentence pattern model by using concept dictionary, i.e., concept identifiers of EDR electronic dictionary and synsets of Japanese WordNet, and software to calculate their semantic similarity is implemented in Python. Then, based on the knowledge of cognitive neuroscience that "human creation does not create something out of nothing, but the memory of the past is the basis of creation", a database of functions and UXs of existing products and services is prepared as an extension of human memory. Using the database, experiments to coming up ideas for solving problems related to the new coronavirus. From the obtained results, the effectiveness and possibility of the proposed method are confirmed.
We developed a new H-type climber for infrastructure inspection by applying the manufacturing technology for climbers used in space elevator experiments, which have been researched for many years. This inspection climber ascends and descends two belt tethers stretched in parallel, thereby reducing the degrees of freedom around each belt and making the climber more resistant to external disturbances such as wind and to twisting than when ascending and descending a single belt. The climber could move not only vertically but also horizontally and on inclines such as slopes. In addition, multiple climbers could be connected to each other by an aluminum frame, which has the advantage that various inspection units can be installed for versatile inspection. In this development work, we first conducted an experiment to investigate a drive system suitable for transporting heavy objects, and then developed the new climber for infrastructure inspection based on the results obtained. In addition, an optimal synchronous control system for position and velocity was developed as an alternative to the conventional optimal synchronous control system for position alone in order to keep the tilt of the inspection climber horizontal and to control its speed. The climber and control system were verified through simulations as well as actual experiments.
A hobbed gear has pitch, profile, and helix deviations caused by various factors. However it is hard for even experts to specify which factors cause individual deviations from the measured ones. Therefore, a hobbing-machine-diagnosis system could play a key role in identifying the factors from hobbed-gear deviations. Artificial intelligence for image recognition, which is comparatively easy to use, could be appropriate for the system. Generally, a larger number of training data for artificial intelligence could improve the system accuracy, however, it must take a longer time for learning. Besides, efficient learning requires small image data. Typical gear-deviation diagrams are large images that include unnecessary information for the diagnosis system. Therefore, the image data for training have only information on the correlation coefficients between the deviations of two teeth selected at a time. The present paper describes a method for providing image data for learning. The image is the arrangement of correlation coefficients in rows and columns as a grayscale. This paper also describes the relationship between the image and the hobbing problems; e.g., radial or face runouts. As a result, the image data showed clear characteristics for the difference in the periodicity of the hobbing problem, however, did not show clear characteristics for the difference in the directionality.
Lean premixed combustion is one of the most promising techniques to reduce nitrogen oxide (NOx) emissions. However, lean premixed combustors have a narrow stable combustion range compared with diffusion combustors and have a risk of flashback. The combustor does not usually have a constant cross-sectional shape due to production restrictions. It is important to analyze the propagation behavior of the lean premixed flame in the swirl flow in the tapered glass tube where the cross-sectional shape changes and the acceleration or deceleration flow exists. In this study, we presented a visualization of the propagation behavior of lean premixed flame in two tapered tubes. One of the quartz glass tubes expanded toward the tube outlet (Tube A) and the other one narrowed toward the tube outlet (Tube B). The inclined angle of both tubes was 1.6°. We visualized the unburned flow and flame behaviors with swirl flow whose swirl vane angles were 15.0° and 22.5°. The reverse flows in the unburned condition were appeared along the center axis in tube A with 22.5° of vane angle. On the other hand, the reverse flows in the unburned condition did not appear in tube B with 22.5° of vane angle, and the flow was accelerated. The flame propagated along low-velocity flow caused in the center axis in tube A. The flashback in tube B with 22.5° of vane angle was occurred in an extremely lean condition as compared with 15.0° of vane angle. In tube B, a reverse flow field was not observed in the unburned conditions, but a reverse flow region occurred upstream of the flame tip in the swirling flow with 22.5° of vane angle.
In this paper, a simple simulation strategy for sintering ceramics is proposed by referring to the experimental results of the deformation profile obtained from a thermomechanical analysis (TMA) under uniaxial compression loads. Assuming that mechanical and thermal deformations are independent, the total deformations are decomposed into mechanical and thermal components, and each deformation component is divided into reversible and irreversible deformations. The thermal and mechanical reversible deformations are represented by the commonly accepted models, namely thermal expansion and linear elasticity. For the thermal irreversible strain (sintering strain), the Master Sintering Curve (MSC), which considers microscopic thermodynamics from a macroscopic perspective, is employed. This facilitates the prediction of any densification evolution without stress and decreases the number of experiments required for parameter fittings. The viscoplasticity model is used for the mechanical irreversible strain to represent the creep deformation in sintering ceramics under stress. In this model, the temperature dependence of the viscosity parameter and density dependence of the yield stress are introduced. The sintering simulation was performed by installing a model with a User Programmable Feature (UPF) into ANSYS thermal–structural analysis. The simulations were validated by comparing the simulation deformation profiles with other sintering experiments under uniaxial compression loads that were not used for the modeling.
Titanium dioxides (TiO2) nano-rods array were fabricated on a fluorine-doped tin oxide (FTO) substrate leaving an array of star-like photoresist patterns array with regular spacing. The patterns were fabricated with a lithography, and the photoresist masked the hydrothermal process, in which chemical reactions proceeds in a sealed container at elevated temperature and pressure to produce regular structure of specific materials. Synthesized TiO2 rods became single crystal rods and aligned perpendicular to the substrate because its lattice constant is similar with that of the substrate. Typical height was 3.4 μm after 4 hours synthesis. Using the superhydrophilicity of TiO2 after irradiation with ultraviolet light, the hydrophobic star-like areas were surrounded by hydrophilic TiO2 area. On the tapered area of each star, the spread oil is ideally gathered at the center of the star due to the imbalance of interfacial tensions in water, which helps the oil droplet repellency. The functionality was evaluated with two experiments. One is the floating test in which the substrate was dipped into water with an oil droplet. The best case showed the droplet float in water. Another is the sliding angles measurement of oil droplet in water. It was found that both of the samples with/without pattern showed small sliding angle as approximately 10 °. The patterned sample showed longer functional life than that without pattern after one week. It was also found that the water trapped between the TiO2 rods assists in repelling the oil droplet.
In this paper, the simple dynamic model for calculation of the axle-box acceleration (ABA) is established for conveniently detecting rail breakage on trains. Track circuit based signaling system, whose functions are detection of vehicles and rail breakage, is tend to be replaced by Communication Based Train Control system because it is expected to reduce the cost for maintaining equipment along railways. In order to maximize the advantage of reduction in costs, the way to detect rail breakage on the vehicles should also be established. The running tests on the rupture part of rails on a ballasted track and a ballasted ladder track are conducted, and the ABAs obtained in each test are analyzed. The dynamic models corresponding to two types of tracks consist of beams on elastic foundation are established. Subsequently, simple vibrating models are derived from beams so as to consider the frequency characteristics of coupled vibration with tracks and vehicles. The results show that the difference of boundary conditions on rails changes the masses and springs contributing to vibration of the systems, changing the eigenvalues of vibration. These changes are reflected to the ABAs in such a way that a peak of resonant frequency of them gets lower when a vehicle running through broken rails. It is assumed that the rail breakage can be detected without wayside infrastructures by acquiring the ABAs and monitoring the change of them in the frequency domain.
To predict the wheel/rail profile wear theoretically with dynamic model of the vehicle-track systems, the wear coefficient is necessary and these parameters are generally derived from laboratory tests, such as twin disk test or a pin-on-disk test. Experimental studies are very useful because the parameters that affect wear development are controlled and also the effects of the parameters on wear development could be evaluated with physical meanings. However, it is not sure that the obtained wear coefficient is applicable to the practical systems or not, because the environmental conditions in the indoor laboratory differ from the actual ones. In this study, a novel method for deriving a macroscopic wear coefficient that takes into account various conditions in the field is proposed and analyzed its effectiveness. In the case of a railway system with vehicles of the same type run on the dedicated track with the same operation pattern such as the Tokaido-Shinkansen, it considers that the rail wear at a specific position is a result of reflecting almost the same contact conditions. Therefore, the method proposed in this study is considered to be effective. The wear coefficient derived from this method are compared to those of the previous studies.
Since axle journal roller bearings of the bogie of rolling stock are important components for the running of the vehicles, early detection of damage to axle bearings is required. Therefore, we developed an autonomous damage detection system "ADDS" as one of the detection devices. The ADDS uses energy harvesting technology that utilizes the power generation function of the piezoelectric element “PZT”. The ADDS can detect axle bearing damage and transmit obtained data to receiver that will be installed under floor of the vehicle without a power supply and cable connection from the vehicle body. In the ADDS, the anti-vibration rubber for axle springs, which is installed on the axle box is replaced by an autonomous damage detection anti-vibration rubber "ADDAR". The ADDAR contains the PZT as a power generation module “PGM” and a transmitter that transmits the detected data to receiver. The transmitter in the ADDAR can be driven by electric power from the PGM. The rotational test to evaluate the performance of the ADDAR was carried out using an axle journal bearing performance rig. The test results show that the power generation performance of the PGM of the ADDAR installed on the damaged axle bearing is higher than that of the ADDAR installed on the normal axle bearing. It is confirmed that the transmitter in the ADDAR installed on the damaged axle bearing can transmit the obtained data to the receiver. Additionally, the power generation performance of the ADDAR is improved when the PGM is installed directly above the damaged location of the axle bearing. In this case, the ADDAR can secure the power to drive the transmitter even at low rotational speeds.
In order to minimize the fuel cost for heating steel ingots in hot rolling process, it is important to plan (1) batch formation to increase filling rate in furnaces and (2) work schedule to reduce stagnation of ingots in furnaces. A low filling rate increases fuel cost per ingot, and stagnation causes additional fuel cost to keep ingot’s temperature. However, the conventional divide-and-conquer methods cannot realize both high filling rate and small stagnation because of planning batch formation and work schedule sequentially. Therefore, we developed a new scheduling method that plans batch formation and work schedule simultaneously by creating multiple candidates of batch. As a result of the computational experiment, the development method reduced 12.3% fuel cost per production compared to the conventional method. The developed method has been applied to actual hot rolling line and reduced the fuel cost by 8%.
Inspection using magnetic sensors based on the magnetic flux leakage testing method as soundness evaluation of wire ropes is being performed. Recently, it has been studied as detailed soundness evaluation method of the wire rope by analyzing the measurement data of multi magnetic sensors as an image grayscale. However, this is the position detection of breakages only rope axis direction. For this reason, if it is not the position detection of breakages on the rope circumferential direction, it is difficult to determine soundness evaluation of wire ropes. It served as the axis of the feature classification plane of the adjacent magnetic sensors extracted by signal-to-noise ratio(SNR) from the measurement results of the detection test of the strand out using rope tester in this study. It was shown to be useful for quantitative evaluation of breakages in the rope circumferential direction by using the information between magnetic sensors. In addition, a single magnetic sensor which is a conventional method compared to the method for determining breakages seeking extracted threshold characteristic quantity by SNR, showed that this method is useful. Finally, it showed that by combining evaluation methods of breakages in the rope axis direction which focuses on the sum of the output values of multi magnetic sensors and the research methods are useful as wire ropes soundness evaluation.
In order to investigate the vibration characteristics of railway vehicle carbodies, some sorts of analytical models have been proposed, such as simple beam, box-type, and finite element models. These models are constructed based on the equations of motions for some assumed or approximated structures. In this study, the authors utilize another modeling technique, without such assumptions or approximations. The model is based on the mass, damping, and stiffness matrices (spatial matrices) of the objective structure, which are identified with use of the frequency response functions (FRF) obtained in the stationary excitation tests. The method is firstly evaluated with a 4-degree-of-freedom system, and then applied to an actual railway vehicle carbody. It is confirmed that the identified spatial matrices properly represent the relation between the excitation force and response vibration even if the degree-of-freedom of the actual system is unknown. And also, the authors try to utilize the spatial matrices to estimate the effects of certain vibration reduction devices such as dynamic vibration absorbers attached to the carbody.
Water spray is used for cooling intake air of gas turbine in thermal power plant. It is necessary to reduce the amount of residual droplets by optimizing the spray amount to keep the plant in good condition. In the actual thermal power plants, a phase Doppler anemometry (PDA), which can provide droplet velocity and diameter of spray, is difficult to apply because it requires precision setting. In this study, a new method for determining the residual droplet flow rate using the laser transmittance for the cooling water spray which can be used at thermal power plants is proposed. A laser transmission method system was applied to a scale-down model of an inlet duct at a laboratory in order to confirm the system reliability. The same types of weather louvers, eliminators, and nozzles installed in the actual thermal power plants were used in the experiment. The effects of optical path length, spatial distribution of spray, flow on conditions, etc. to the measurement accuracy were evaluated at the model case experiment in the laboratory. The residual droplet flow rate calculated by the laser transmission method and that of the PDA measurement are compared. The error of the residual droplet flow rate calculated by the proposed method was about 12.8%. The proposed system was applied to an actual thermal power plant. At the thermal power plant, the residual droplet flow rate was reduced to about 35% by the eliminator compared to the case without the eliminator. Since the residual droplet flow rate can be measured by the laser transmission method, it can be used for optimizing the spray amount in actual thermal power plants. Compared to other methods, the proposed method allows the experimental equipment to be also constructed relatively easily. It is easy to install in an actual thermal power plant. The experimental results demonstrate the effectiveness of the present apparatus as a relative evaluation method.
The crash safety structure of the railway vehicles is important as one of the safety measures against the train crews and the passengers in the event of a collision accident. It is impractical to perform collision testing many times using the actual train unit to design the crash safety structure, whereby the numerical simulation is effective and it is important to validate the analytical accuracy. However, there are few studies of collision tests and numerical simulations using actual size carbody structures according to Japanese design standards, and even fundamental data have not been sufficiently obtained. Therefore, firstly, the authors performed the collision test of an actual-size partial stainless-steel carbody structure of a railway leading vehicle against a rigid wall and finite element analysis under the same condition as the test for the purpose of validating and improving the analytical accuracy of numerical simulation. Secondly, we carried out the collision test of the same carbody structure of a railway leading vehicle against a typical large dump truck in Japan and obtained the fundamental data such as the time histories of the impact compression load and the acceleration of the carbody structure as well as the deformational and fractural behavior of them. We also performed FE analysis under the same condition as the experimental test and compared the numerical result to the experimental one. As a result, the numerical result was consistent with the experimental result. Finally, we expanded the partial carbody structure model to a single carbody model and carried out the collision analysis of it against a large dump truck. Thereby, the impact deformation and fracture behavior of the railway carbody under the actual level-crossing accident were estimated.
Wheel cleaving is one of the dividing methods of glass substrates, and is widely used in industrial scenes like manufacturing of flat panel displays. However, the crack generation mechanisms are not fully understood and therefore, the processing conditions are determined empirically. In this study, we observed crack generation behaviors during loading/unloading processes of toothed wheels by using highspeed imaging system. Finite element method (FEM) analysis of stress distribution in glass substrates were also carried out. As a result, two types of vertical cracks (circular and half-penny cracks) were observed just below the scribing wheel. Depending on the wheel shapes and applied load, the generation behavior of these cracks varied. Numerical results suggested that the crack generation behavior was determined by whether the tensile stress field was distributed up to the glass surface where some defects existed formed by wheel contact. This means low-height tooth and high applied load conditions produce a compressive stress field at the vicinity of glass surface, and the vertical crack generation is suppressed. To obtain a smooth cleaved surface, the half-penny crack generation during loading process is essential. For this purpose, precise control of indentation depth by optimizing wheel shape (tooth length, height and span) and applied load is necessary.
Lure fishing is a special fishing method that using artificial fishing lures as fish baits and has become more and more popular all over the world. Vibration lures are a regular item among fishing lures that perform vibration action in the water for baiting fish. In the present work, to enhance the vibration behavior of vibration lures with a real analytical condition, we propose a free-form optimization method for fundamental frequency maximization design problem of solid structures considering initial stress and apply it in shape optimization of vibration lures. We use the fundamental frequency (i.e., the 1st order) eigenvalue as the objective function and maximize it subject to a weight constraint. As the optimal results, the fundamental frequency eigenvalue of a vibration lure made of Zinc could be enhanced to 2.20 times as much as its initial value under initial stress conditions induced by water pressure and tractive force of fishing line, while the mass of the optimal shape satisfied the mass constraint during the optimal design process. As a comparison, we also perform a design optimization of the vibration lure without considering any external loading, whose fundamental frequency can be also enhanced over 2 times as much as its initial value.
Automation is currently delayed in garment factory. In order to automate the work in a garment factory, a method of single sheet separation from piled fabric is required. In this study, we developed a method of single sheet separation from piled fabrics by a roller hand mechanism with a rotating mechanism added to the tip of a robot hand. We designed a rigid body dynamics model for separating a sheet of fabric by this mechanism, and conducted experiments on the separation of a sheet of fabric. As a result, we succeeded in separating only single sheet of fabrics with a high probability. It is necessary to eliminate failures for practical use. However, it is difficult to eliminate failure completely due to the characteristics of fabrics. First, in order to improve the reliability of the separation process, we devised a method to determine the success of separation by the thickness of fabrics, created a mechanism and actually verified. We have succeeded in improving the reliability of single sheet separation process from piled fabrics. However, there was a failure pattern that cannot be addressed by this method. Therefore, we devised a method to determine the success of separation by the weight of fabrics, created a mechanism and actually verified. As a result, the reliability was further improved.
A micro-machined thermal flow sensor called “Flow Vector Sensor (FVS)” can measure an airflow speed and its direction simultaneously. The FVS is extremely small, and hence it does not disturb flowfields around the sensor. In addition, since a response time of the FVS is very short, the FVS can measure unsteady flows. Therefore, the FVS is expected to be applied to flowfields over various objects such as automobiles. However, when the airflow speed is high, the sensitivity of the prototype of the FVS tends to be lower. In this study, we numerically examine heat transfer from the FVS to the airflow, in order to improve the sensitivity of the FVS in a high-speed airflow. First, we investigate the heat balance between the FVS and surroundings, in order to identify the cause of the lower sensitivity of the FVS. The heat transfer between the FVS and airflows is found to affect the sensitivity of the FVS, especially in the high-speed airflow. Second, we examine the effect of the size of the FVS, in order to discuss the design philosophy of the FVS. The heat transfer from the FVS to airflows is found to decrease with decreasing the size. Consequently, the small size of the FVS can improve the sensitivity of the FVS. These results should provide new insights into the design philosophy of a high performance FVS.
When a rigid and small subsystem is rigidly coupled to a main system of a design target, it would be helpful if the multiple resonance frequencies moved by this coupling could be properly assigned so that they do not coincide with the peak of excitation frequencies to avoid resonance. In this paper, a rigid and small subsystem is regarded as a rigid body, and a visualization design method to optimize the assignment of multiple resonance frequencies is developed through the design of the mass matrix of the rigid and small subsystem. In this method, the mass matrix is diagonalized by using the principal axis of inertia of the rigid body, and then the frequency band that satisfies the resonance formation condition is predicted by the kernel Compliance Analysis. Furthermore, by combining this method with Weyl's inequality theorem, we made it possible to design the assignment of multiple resonance frequencies while looking at a single figure.
This paper presents a method for reducing vertical vibrations in a railway vehicle carbody by supporting underfloor equipment using high-damping elastic mounts. This is a kind of dynamic vibration absorber utilizing underfloor equipment as a mass element which has been introduced based on the inspiration of the damping effect of passengers. Numerical studies were firstly carried out to check the feasibility of the idea using simple two degree of freedom model representing carbody and underfloor equipment. Then a prototype of the elastic supporting member was built as a simple rubber mount and two type of excitation tests were conducted using a Shinkansen type test vehicle. The authors conducted excitation tests in the rolling stock testing plant to examine the carbody vibration reduction effect due to track irregularity. As a result, two dominant peaks in the acceleration power spectrum densities of floor corresponding to different elastic vibration modes were reduced simultaneously when the proposed method was applied. The vibration reduction effect became large as the elastically supported mass of underfloor increased. Then, to examine the vibration isolation performance of the developed rubber mount, excitation tests were conducted by a vibration exciter installed on the underfloor equipment. From the random wave excitation, the authors confirmed that the vertical vibration of carbody floor is reduced over a wide frequency band.
After the Mid Niigata Prefecture Earthquake in 2004, research and development of earthquake countermeasures has started for Shinkansen trains. Some technologies for improving running safety of the Shinkansen trains during an earthquake have been applied to commercial lines and vehicles. Regarding conventional lines, earthquake countermeasures are also taken a growing interest, especially in metropolitan areas. At first, conventional guard angles which are usually placed on sharp curves are considered as the earthquake countermeasures due to cost restrictions. For the trains which have yaw dampers, this paper proposes to change the layout of the yaw dampers to longitudinally symmetrical position in bogie as another countermeasure against an earthquake. This paper also numerically clarifies that the proposed layout of yaw dampers improves running safety against sinusoidal oscillation. In addition, the actual bogie oscillation test is performed to valid the numerical results. From probabilistic perspective the authors show that the conventional guard angle and the proposed layout of yaw dampers have almost the same effects on improving running safety for seismic vibration of track.
This paper starts with describing a method of deriving the resonance mode of a pendulum utilizing its equation of motion. Its resonance mode is that the particle accelerates toward the equilibrium position in the vertical plane including its fixed point. Therefore, a resonance mode can be derived by finding its equilibrium position and something to accelerate from its equation of motion. To derive the yaw resonance mode, the former paper transformed the equation of motion of vehicles into a structure that matches the equation of motion of the pendulum by assuming a special vehicle speed. This paper derives the yaw resonance mode at general velocities by modifying the variables that satisfy the configuration of the equation of motion derived in the former paper. As a result, this paper found that the yaw resonance equilibrium position is on the vehicle speed vector at the position where the side slip angle of the vehicle body is 0 in a steady state turning. This paper also found that something that accelerates towards equilibrium is the rear wheel. This acceleration of the rear wheels toward this extension is the restoration of yaw resonance.