This study deals with a tilt control pattern design for a tilting train using air springs. When a railway vehicle travels on a curve, the tilting system tilts the car body by supplying compressed air to the air springs on the outer rail, causing them to expand. However, when the vehicle runs on a railway track with continuous curves, there is a possibility that the vehicle may run out of compressed air. Therefore, in this study, based on the compressed air consumption estimated from the internal pressure of the supply air reservoir, a tilt control pattern that reduces the car body tilt angle was generated. The tilt control pattern for continuous operation of the tilting system was calculated using dynamic programming. To calculate the tilt control pattern, a four degrees of freedom model combining a simplified vehicle model and a supply air reservoir model was used. For simplicity, a condition for continuous operation of the tilting system was that the internal pressure of the supply air reservoir did not fall below the internal pressure of the air spring. Under this constraint, we generated the tilt control patterns for a route with continuous curves with the same curvature. As a result, by selecting curves with shorter circular sections and generating tilt control patterns with reduced tilt angles on those curves, continuous operation was enabled, although ride comfort deteriorated.

This paper presents the results of a validation study assessing the adequacy of a method proposed in a previous study, which continuously measures the lateral contact position between the wheels and rails of a railway vehicle. A series of tests were conducted at speeds of up to 30 km/h using a railway vehicle equipped with an instrumented wheelset specifically designed to measure the contact position. This wheelset had been fabricated as part of the earlier study. Consequently, it was confirmed that the proposed method is capable of continuously measuring the contact position, even during wheel climb events. However, there were instances in which the contact position could not be determined. Periodic fluctuations caused by computational errors were also observed; however, these were effectively mitigated through a moving average processing. The inability to determine the contact position was primarily attributed to high-frequency fluctuations (approximately 300 Hz) in the bridge output and computational errors inherent in the proposed method. The former is considered to have minimal impact when the contact position is measured at approximately 100 Hz. The latter affects the filtered contact position at 100 Hz, but its influence can be reduced through moving average processing. To further verify the adequacy of the proposed method, the authors conducted a direct measurement of the contact position using paint. This was achieved by photographing the areas of the wheel tread where the paint had been removed due to contact with the rail. A comparison with the moving-averaged contact positions revealed a discrepancy of approximately ±2 mm, thereby confirming the sufficient accuracy of the proposed method.

On railway vehicles, when passengers get on or off, their luggage and other objects can get caught in the doors. If the object caught is large, the pinching of the object is detected by the current door pinching detection device (DPDD). In such a case, the vehicle will not be able to move. On the other hand, it is difficult to detect the pinching of narrow inclusions with the current DPDD. As a result, there is a possibility that the vehicle moves with the inclusion pinched in, or that the inclusion will cause the passenger to be dragged. Therefore, in order to detect these events, we have developed a door pinching detection system (DPDS) using a door rubber with a built-in pressure-sensitive sensor (DRBPS). The DRBPS can detect the pinching of inclusions with a diameter of 8 mm or larger, and can detect dragging that occurs outside the vehicle with a load of approximately 150 N or less. The DPDS can easily transmit the detection information obtained by the DRBPS to security equipment using a non-contact power supply, and can be easily installed in existing vehicles. The results of one year of operation with DPDS installed in real vehicles showed that no missed detections or false detections occurred, although some detections were caused by contact with the low-risk rubber end of the door.

It is well known that rubber suspensions, which are used in railway vehicles, change the characteristics in vibration transmission such as stiffness over time. This ageing property affects the vehicle running performance. However, the method for predicting such ageing property of railway rubber suspension is not well established. This paper describes the modeling method to calculate the change in stiffness of rubber suspension in the long-time usage for improving the long-term reliability of the vehicle. In this paper, the thermal oxidative degradation, which is one of the major degradation factors in rubber, is discussed. Firstly, heat accelerated ageing test of the rubber block is carried out to obtain the heat ageing properties of the rubber material used in railway suspension. The ageing test results show that the change in strain energy of rubber is dependent on heating time, distance from the surface of rubber block, and strain amount of rubber. Secondly, these heat ageing properties are modeled as the mathematical equations based on the heat ageing test results. The change in stiffness of rubber block due to thermal oxidative degradation is predicted with FEM simulation using the material constants generated by these mathematical equations. By comparing calculation and test results of increase in stiffness after heat ageing, the calculation results with the proposed method are in good agreement with the heat ageing test results. And finally, rubber stiffness change under the thermal oxidative degradation at the operating ambient temperature is evaluated using a formula for the temperature dependence of reaction rates. The results show that the increase of rubber stiffness is large at high operating temperature. Moreover, the results also show that the amount of stiffness increase is affected by the size and shape of rubber suspension.

The contact characteristic of a tire is fundamental property that significantly influences handling stability, ride comfort, and environmental performance such as rolling resistance and wear. Although it has been experimentally confirmed that the rolling contact pressure distribution of a tire exhibits circumferential asymmetry, a theoretical interpretation of this asymmetry is not self-evident. This study proposes a new tire mechanical model that calculates contact pressure distribution during tire rolling. The proposed model is a tire model that integrates a three-dimensional elastic ring model and brush elements of tread. The brush elements representing the tread exhibit variable stiffness, designed to emulate the hysteresis behavior of tires as confirmed through experimental observations. The validity of the proposed model was verified using an inner-drum tire testing machine equipped with road surface segments embedded with force sensors. In this model validation, the model parameters for sidewall and belt stiffness were theoretically calculated from tire design parameters, while the tread stiffness parameters were identified based on experimental results. The validation showed that the proposed model qualitatively reproduced the measured rolling contact pressure distribution with circumferential asymmetry in the contact plane. The proposed model is expected to be utilized in design studies aimed at achieving the desired tire contact pressure characteristics.

In some slab tracks in cold regions, freeze-thaw cycle causes frost damage to the slab track filling layer. To evaluate this phenomenon, we proposed a weakly coupled analysis method of heat balance calculation on the slab track surface and heat conduction inside the cross-section using the all-sphere visible element. The all-sphere visible element is the element at the end of the line of sight from each part of the surface in all directions, and is represented using a three-dimensional polar coordinate system. Calculations of solar radiation and longwave radiation based on the all-sphere visible element allow detailed modeling of the thermal energy received by the slab track surface from its surroundings, taking into account the shade of the railway structures and other factors. The proposed method was applied to actual slab tracks to numerically reproduce the freeze-thaw cycle in winter. The root mean square error of the analytical results for the measured temperature of the slab track was 1.45 °C for the track slab and 1.38 °C for the filling layer. In addition, the temperature and the number of freeze-thaw cycles were compared for the up and down lines and their left and right sides of the slab track. The results showed that the left side of the up line, which receives the least amount of solar radiation and is farther from the wall, had the lowest nighttime surface temperature and the highest number of freeze-thaw cycles. These results indicate that daytime solar radiation and longwave radiation from the wall mitigate the nighttime temperature drop and freezing, and that the frequency of freeze-thaw can vary depending on the positional relationship between the sun, orbit, and wall.

The maintenance standard values for track irregularity at high-speed type turnouts where trains pass through the main line of turnout at a speed of 120 km/h are managed with stricter values compared to general turnouts. The target track irregularities are longitudinal level irregularity, alignment irregularity, and cross level irregularity. The maintenance standard values for these irregularities of high-speed type turnouts are approximately half of those for general turnouts. This resulted in significant labor and maintenance costs. These values have been empirically determined from running tests conducted in the 1980s. However, since these values were determined empirically, the quantitative validity of these values has not been verified. Therefore, in order to optimize maintenance, it has been necessary to clarify the adequacy of standard maintenance values for track irregularity at high-speed type turnouts on the basis of quantitative technical evidence. This study developed a vehicle running simulation model on turnout using 3D dynamic finite element method (FEM) to quantitatively evaluate the effect of track irregularity on the damage to turnout components. Furthermore, using the developed simulation models, we carried out various studies on track irregularity. As a result, it was found that when alignment irregularity exceeds the current maintenance standard value, it has a significant impact on the damage to track and signal components. Therefore, it is desirable to manage alignment irregularity within the current maintenance standard value. On the other hand, it was found that longitudinal level and cross level irregularity have a small impact on the damage to these components, even when the track irregularities exceed the current maintenance standard value. From these results, it was clarified that the maintenance standard value for longitudinal level and cross level irregularity can be tolerated up to 23 mm, which is the same value as that for general turnouts.

We investigate the deformation behavior of the ballast layer under a grid-type sleeper, using the elastoplastic FEM with the extended subloading surface model. In the elastoplastic FE analysis, we have to utilize the time history of the sleeper reaction as the external force in the FE-based simulation. The time history of the sleeper reaction is evaluated using a wheel-track vibration analysis. Through numerical tests on the jointed track with a suspended joint, the use of the grid-type sleeper leads to the reduction of the ballast settlement.

Prestressed concrete sleepers (PC sleepers) are an important component of railway tracks. The dynamic response of PC sleepers to passing trains is influenced by various factors relating to the vehicles and tracks. However, few studies have quantitatively evaluated the relationship between wheel surface roughness and the bending moment of PC sleepers. In this study, we measured the wheel surface roughness of the target vehicles under normal use conditions and the bending moment of PC sleepers when the vehicles passed over them on the commercial line. Additionally, we quantitatively evaluated the relationship between wheel surface roughness and the bending moment of PC sleepers using numerical analysis, the validity of which was varied through comparison with field measurement results. The results were as follows: 1) A wheel flat with a dip of about 0.5 mm was measured. 2) Compared to the roughness spectrum of a wheel without a wheel flat, the wheel flat increased the roughness level at spatial frequencies of between 10 and 100 m^-1. 3) No significant difference was observed in the measured bending moments between vehicles with and without wheel flats. 4) This is because the influence of the measured wheel surface roughness on the bending moment was smaller than that of the rail roughness. 5) Numerical analysis showed that when wheel flat length is 75 mm or more, the bending moments peak at low vehicle running speeds of around 15 km/h. At a wheel flat length of 75 mm, the bending moments are up to 3.7 times greater than when there is no wheel flat. 6) The rounded wheel flat shifted the speeds at which the bending moment peaks to higher speeds, but had little effect on the maximum value. 7) Of all the track parameters, the spring constant of the rail pad had the greatest influence on the bending moment.

Diesel engines are internal combustion engines with low fuel consumption. However, CO₂ emission such as a greenhouse gas is unavoidable because diesel engines use the hydrocarbon fuels derived from fossil fuels such as diesel fuel and heavy oil. Therefore, diesel engines are required to switch from the utilization of hydrocarbon fuels derived from fossil fuels to the utilization of carbon-neutral fuels such as bio diesel fuel and non-hydrocarbon fuels such as hydrogen and ammonia to prevent global warming. If the mixed-combustion of biodiesel fuel and green hydrogen derived from renewable energy sources is applied to power generation systems using existing diesel engines, it is expected that the power generation sector will become a low-carbonization. If the fuel injection strategy such as fuel injection timing and fuel injection pressure in existing diesel engines are adapted for the mixed-combustion of biodiesel fuel and hydrogen, modification of the ECU control system will be required, which may increase development costs. In this study, the mixed-combustion of biodiesel fuel and hydrogen was applied in the retrofitted diesel engine with hydrogen supply system and without modifying the existing ECU control system. Smoke emission characteristics of the retrofitted diesel engine equipped with a hydrogen supply system were investigated at medium engine speed and light load operating condition (Ne =1640 rpm, BMEP = 0.3 MPa) when the hydrogen supply ratio was varied in the mixed-combustion of biodiesel fuel and hydrogen. As the result, smoke levels in the mixed combustion of biodiesel fuel and hydrogen were lower than the smoke levels in the diesel engine running on BDF only, even though the hydrogen supply ratio increased to 47.4% and the excess air ratio decreased. The reduction of Smoke emission in the mixed combustion of biodiesel fuel and hydrogen is attributed to the fact that as the hydrogen supply ratio increases, the amount of BDF, which contains carbon, supplied decreases.

Fast motion is required for assembly robots. The SCARA type robots are applied for industrial assembly processes. “Standard cycle time” is SCARA robot’s speeding up measure for short-distance motion. Standard cycle time (SCT) has been shortened from about 0.8 s to about 0.3 s over the past 40 years. This shortening is realized by three means. One means is the optimized moving path in the horizontal plane. This study focuses on the moving path and describes a new moving path evaluation method shortening SCT in standard working area (SWA) from a kinematic approach. (1) Evaluation scheme consisting of the partial area evaluation and the whole area evaluation in SWA is explained. Kinematic Time Shortening Measures (KTSMs) (a), (b) and (c) are proposed as an evaluation measure, (a) Summation of horizontal motion angle: δθsum, (b) Manipulability ellipsoid-motion direction intersected line length summation D, (c) Manipulability summation W. (2) As the partial area evaluation, SCT is measured at the center position of SWA (past published measurement) and KTSMs are calculated for the experiment condition. One-to-one correspondence is evaluated between SCT and KTSMs. KTSM (c), which does not have one-to-one correspondence with SCT, is excluded. (3) As the whole area evaluation, optimal moving path and shortened SCT is estimated based on KTSM(a) and (b)’s calculation and step (2) relationship between SCT and KTSMs. Additionally, this result is confirmed that it is in accord with the dynamic model’s estimation. (4) This study describes the estimating method of time shortening moving path by the partial area’s experiment and the whole area’s kinematic calculation without dynamic model.

Recently, wearable leg support systems that can be applied to people with lower limb disabilities have been developed by many researchers. We also have proposed a manual control type leg support system that a user manipulates lever to control a mechanical leg by master-slave control. In the manual control type leg support system, it is important to learn lever manipulation by oneself. Especially, it is a challenge to stabilize standing posture by the lever manipulation. This study aims to clarify a lever manipulation to stabilize the standing posture on the manual control type standing stabilization test system. First, a standing stabilization test system was developed, that a healthy person rides a mechanical system with two mechanical joints to imitate paraplegia person with leg support systems. Second, we found a lever manipulation to reduce undershoot of zero moment point while making rapid posture transitions by using the developed equipment. In the manipulation, the wrist and shoulder started moving in opposite direction with time difference, and the effect to zero moment point from the ankle and hip movements canceled. As a result, the undershoot of zero moment point was prevented.

Herein, a method for evaluating the wheel-flat shape generated during braking in railway vehicles is proposed. Prior studies have not clarified the generation mechanism of wheel-flats, preventing a quantitative estimation of their shape. In this study, we developed a one-way coupled analysis method that integrates vehicle dynamics analysis employing the commercial software SIMPACK and a newly developed wheel–rail frictional heat analysis. In the proposed method, the tangential longitudinal stress was first calculated from the tangential contact force and contact ellipse based on SIMPACK results. Concurrently, the contact surface temperature was calculated via wheel–rail frictional heat analysis. Subsequently, the equilibrium condition of the tangential stress corresponding to the contact surface temperature and tangential yield stress of the wheel steel, obtained via high-temperature tensile tests, was determined by gradually expanding the wheel–rail contact ellipse. Finally, the equilibrium shape was defined as the wheel-flat shape. The validity of the proposed method was verified by comparing the results with measurements obtained for commercial vehicles. Furthermore, a case study using the proposed method demonstrates the generation mechanism of the wheel-flat shape, which is prone to random occurrence.

To reduce the impact of falling, the use of softness by springs and dampers is not sufficient, but the mass of the impacted object has to be reduced. In particular, when an elderly person falls from a bed, even a small impact may cause a bone fracture, despite the large momentum of the person’s body weight. Therefore, the effect of impact reduction has to be high. In this paper, we design a drop impact reduction mechanism that breaks the transfer of the impact force by utilizing the singularity of the mechanism. The kinetic energy of the falling object is converted into kinetic energy of the weight by the mechanism, and the energy is dissipated when the weight collides with a wall. Singularity breaks the impulsive force transfer generated by the collision of the falling object with the mechanism and the collision of the weight with the wall. After demonstrating that the mechanism breaks the impulsive force based on kinematic analysis, the operation of the mechanism is verified using a small prototype. The proposed mechanism is extended to a size that can support a human fall, and the effectiveness of the proposed mechanism is verified through experiments.

As semiconductors become more capacitive and sophisticated, 3D packaging technology is gaining increased attention. Since multiple chips are stacked in such configurations, the wiring structure becomes more complex, leading to stress concentration. In addition to thermal stress, mechanical vibrations may also be applied, raising concerns about potential wiring failure. Aluminum and copper are commonly used as wiring materials. Traditionally, measuring the fracture strength of thin films required preparing a single-layer film specimen. However, because thin films are not self-supporting, special specimens and testing equipment were necessary.To address this, we have developed a multilayer bulge method. In this method, the test specimen is supported by a silicon substrate approximately 1 mm thick, which improves handling and simplifies the testing apparatus. In this study, the multilayer bulge method was applied to evaluate the fracture strain of aluminum films, yielding the following results. The fracture strain of the aluminum film was estimated to be between 3.3% and 4.2%. This value is approximately one-tenth of the fracture strain of high-purity (99.99% or 99.9999%) aluminum with a thickness of 1 mm. This reduction is presumed to be due to the thin film structure and the presence of an underlying layer, which inhibits dislocation growth.

Short fiber reinforced rubber composites (SFRRCs) are crucial, lightweight, and durable materials used across various industries. We've developed a simulator for full rubber belt-pulley friction contact behavior utilizing the large-scale parallel FE structural software FrontISTR. However, accurately integrating SFRRC's complex material behavior into this already large-scale simulation presented a significant challenge: traditional solid element modeling for both rubber and fibers proved impractically expensive. To overcome this, we developed and added an insert element function to FrontISTR. This function represents short fibers as embedded truss elements within the solid rubber matrix and supports distributed-parallel computation based on domain decomposition. The proposed method was verified by comparing the results obtained using the specimen model with actual short fiber orientations to those from commercial software. Our approach significantly reduces the computation time, achieving a speed-up of 400 times compared to conventional analysis with solid elements.

An aliasing type reducer, which fulfils both a high reduction ratio and low vibration in a thin and small body, had been proposed to cope with the further downsizing of DC motors. This reducer consists of two disks with sinusoidal grooves of the same amplitude but different periods, bearing balls rolling in grooves, and a disk with oval holes formed at equal intervals around the circumference through which the bearing balls can move radially. The two grooved disks sandwich the disk with bearing balls in its oval holes, and the bearing balls are held at the intersections of the two types of grooves. The disk with the groove of larger period works as the input plate, the disk with the oval holes as the output plate, and the other grooved disk as the stator, respectively. The reduction mechanism is inspired by the "sampling theorem." As the input plate rotates, the bearing balls engaged with each groove reciprocate radially within the oval holes, decelerating the output plate and rotating it in the same direction as the input plate. It is confirmed that the prototype has extremely small output torque fluctuation during power transmission, and that the idling torque is as small as that of a planetary gear reducer. However, the torque transmission efficiency is only 70%, which is significantly lower than that of a planetary gear reducer. This is thought to be due to the slip friction between the bearing balls and the grooves, and is a forthcoming challenge.

A cerebral aneurysm is a disease in which an artery in the brain expands like a balloon. It has a high probability to be fatal if it ruptures so it is very dangerous. One of the surgical operation techniques is stent placement. Stents are devices used to treat cerebral aneurysms. The shape is cylindrical, and the configuration is braided with multiple metal wires. At present, the deployment technique and selection of the braided stent greatly depend on the experience of the doctor. Therefore, we propose the new deployment technique for braided stents. This is a technique that achieves both blood flow suppression and controllability of a braided stent. We verified these issues by finite element method simulations. The finite element analysis all steps that deployed configuration including braided stent crimping, delivery and expansion. The braided stent is placed in a virtual vessel model. Techniques were compared with multiple patterns of braided stent surface direction. Our proposed technique reduced the porosity of the cerebral aneurysm orifice. It suggests that the proposed technique has the potential to improve blood flow velocity suppression compared to the base technique.

Monitoring wheel-rail contact forces is essential for ensuring railway operational safety. The derailment coefficient, defined as the ratio of lateral force to wheel load, is a critical parameter for assessing the risk of flange climb derailment. The PQ monitoring bogie has been developed to monitor this coefficient, with wheel load estimation currently based on the vertical displacement of the primary suspension. However, this method does not account for factors such as lateral forces on the wheelset and the dynamic geometrical relationship between the wheelset and wheel-rail contact points, leading to estimation inaccuracies. These inaccuracies are particularly pronounced on sharp curves due to stronger lateral force effects. This study proposes an enhanced method for wheel load estimation in PQ monitoring bogies by utilizing the bogie’s measurement capabilities. The proposed method is formulated by solving the quasi-static equation of equilibrium on curved track sections, incorporating the effects of lateral forces and dynamic variations in the lateral distance between the wheelset and the wheel-rail contact points. Since some input variables required for the proposed method cannot be directly measured, estimation techniques using lookup tables referenced by the train’s position along the track are also introduced. The accuracy of both the conventional and proposed methods is evaluated through multi-body dynamics simulations and on-track testing. Overall, simulation and test results demonstrate that the proposed method significantly improves wheel load estimation accuracy, especially on sharp curves, compared to the conventional approach.

This study aims to develop switching and adjustment devices for switch rails, proposing a point of turnout that contributes to reduced maintenance efforts. First, the authors designed and produced a switching device that replaces the electric point machine, enabling monitoring of the switch rail position and switching force. Secondly, we designed and produced adjustment devices that adjust the gap between the switch rail and the stock rail through expansion and contraction after switching. The developed devices were installed on a turnout, and a series of performance tests were conducted. As a result, we confirmed that the devices enable early detection of switching failures and automate the inspection and adjustment of gaps. Additionally, a running test with a vehicle passing over the turnout confirmed that the devices functioned normally both during and after the vehicle's passage.