This paper proposes the fluorescence response-based optical probing (FROP) method for the 3-dimensional measurement of precise products. Several 3-dimensional measurement methods exist, such as micro-coordinate measuring machines, confocal microscopy, and point autofocus microscopy. However, measuring precise products with small, smooth, and steep (3S) structures—such as die molds and optical lenses—remains challenging. In this study, we propose a new surface detection scheme that utilizes autofluorescence from the sample surface. Unlike reflected light, fluorescence is emitted over a wide angle. Therefore, the optical response from the surfaces of 3S structures can be obtained by exciting fluorescence at the measured surfaces. This paper first explained the principle of FROP. Next, the fundamental FROP signal was examined on surfaces tilted at different angles. The FROP successfully detected vertical and even overhanging surfaces, demonstrating its strong potential for 3-dimensional measurement. The principle of surface position determination was then verified through comparisons with conventional confocal microscopy for 2.5D measurements, and thickness measurement results were compared with micrometer results. These results revealed that the peak position of the differentiation signal in FROP coincided with the sample surface. Finally, a 3-dimensional 3S structure was measured. The results confirmed that vertical surfaces could be successfully measured using the FROP method, whereas conventional confocal microscopy could not measure them. Consequently, the performance of FROP for 3-dimensional measurement of precise products was validated.

In recent years, the proportion of elderly individuals in Japan has been increasing, accompanied by a rise in the number of patients with osteoarthritis. In particular, artificial joints, which are effective in treating knee osteoarthritis, commonly use Co-Cr-Mo alloys (CCM alloys) for their sliding surfaces due to their ability to suppress uneven wear. However, conventional CCM alloys pose a problem during sliding use, as they generate biotoxic metallic wear debris. To address this, high-carbon Co-Cr-Mo alloys (HC-CCM alloys) with improved wear resistance have been developed. Nevertheless, there have been few studies on the machining of HC-CCM alloy with end mills. This study investigates the high-speed machining of HC-CCM alloy using radius end mills, focusing on the influence of tool material and cutting speed on cutting performance. The results showed that both carbide and CBN tools reached their tool life limit within a short cutting length. In contrast, the binderless nano-polycrystalline cubic boron nitride (RcBN) tool exhibited excellent wear resistance, achieving a machining length of up to 7.0 km. These findings indicate that the RcBN tool is highly effective for machining HC-CCM alloy. Furthermore, excessive tool damage was observed at cutting speeds exceeding 15 m/s, suggesting that an optimal cutting speed is approximately 10 m/s.

In the present study, we investigated the influence of the magnetization angle of cubic magnetic particles on the internal structure of aggregates by means of Monte Carlo and Brownian dynamics simulations. Monte Carlo method was used to examine the internal structure of aggregates at equilibrium, while Brownian dynamics method was employed to analyze the time evolution of the internal structure during the approach to equilibrium. Monte Carlo simulations showed that face-oriented magnetic moments promote the formation of chain-like clusters, whereas edge- and diagonal-oriented moments lead to closely-packed clusters. Brownian dynamics simulations revealed that the growth rate of aggregates depends on the magnetization direction. As the magnetization angle approached the face direction from the diagonal direction, the internal structure of the aggregates tended to transform from closely-packed clusters to chain-like and ring-like clusters. In particular, a distinct structural transition was observed when the magnetization angle was in the range of approximately 15° to 20° from the diagonal direction. In contrast, changing the magnetization angle from the diagonal direction to the edge direction had little effect on the internal structure of the aggregates, and closely-packed clusters were still observed. These findings suggested that a magnetization direction tilted by approximately 12° from the diagonal direction, as experimentally predicted, was close to the critical angle where a structural transition occurred. As a result, although closely-packed clusters remained the dominant structure, ring-like and chain-like clusters also formed simultaneously within the system.

To reduce carbon dioxide emissions, carbon-free ammonia is being investigated as an alternative fuel for internal combustion engines. When injected into a low-pressure environment, liquid ammonia undergoes rapid vaporization (flash boiling) due to its low boiling point. In this study, the effects of ambient pressure and fuel temperature on spray morphology and tip dynamics of ammonia from a multi-hole injector were investigated under an injection pressure representative of port fuel injection. Visualization was performed in a constant volume chamber. Mie scattering was used to visualize the liquid phase distribution, while schlieren imaging was used to visualize the gas-liquid distribution. The results showed that, as the ambient pressure decreased and the superheat degree increased, the spray plumes from individual holes collapsed and merged into a single spray structure. The spatial distributions of liquid and gas phases remained similar, and the spray remained in the liquid phase up to the tip, regardless of ambient pressure and fuel temperature conditions. With increasing superheat degree, the spray region expanded near the nozzle and narrowed downstream. In addition, the penetration length increased. This increase was quantitatively correlated with the volume expansion caused by flash boiling.

A novel force distribution adjustment mechanism for force sensors is proposed to implement variable admittance control in robotic systems. While admittance control is widely utilized in physical human–robot interactions (pHRI), existing approaches face significant limitations: software-based variable admittance control is constrained by the bandwidth of the robot controller, which can potentially cause instability in high-rigidity environments. Meanwhile, hardware solutions that utilize low-compliance mechanisms lack adaptability to varying operational conditions. This paper developed a novel force sensor-based mechanism that enables variable admittance control through mechanical adjustment of the force distribution between the detection and non-detection interfaces of a force sensor. The proposed mechanism, which is approximately 50% smaller than the force sensor, employs distributed load theory to adjust the gain by varying the contact surface interfaces between the detection and non-detection, enabling stable gain adjustment even in high-rigidity structures. In contrast to conventional beam-based approaches where the range of gain adjustment decreases with increased rigidity, the proposed method maintains variable characteristics regardless of the structural rigidity. Experimental validation through experiments for evaluating the gain adjustment characteristics and spiral groove tracing with Peg-in-Hole tasks experiments demonstrated the gain adjustment capability of the proposed mechanism and verified its implementation of variable admittance control through a simple hardware installation.

This paper presents the development and evaluation of a Mechanical Positioned Guided Vehicle (MPGV), a sensorless and mechanical-control mobile robot designed to achieve high-precision positioning of less than ±5 mm. AGVs and AMRs have traditionally required high-tech sensors and control systems for accurate positioning, however these technologies increase costs and require specialized knowledge for implementation and maintenance. The MPGV utilizes mechanical components and mechanisms to achieve accurate positioning without relying on electronic control and sensors. It features two driving modes: a normal mode, which uses common guidance methods like magnetic tapes, and a guide-rail mode, which mechanically ensures precise positioning. In guide-rail mode, the MPGV is constrained by a guide rail, allowing for straightforward, high-precision positioning using mechanical stops and a wheel lift-off mechanism to decouple power. The paper describes the design and functional principle of key mechanical systems, including transmission and wheel lift-off mechanisms, and conducts experiments to verify the MPGV’s functionality and precision. Experimental results show that the MPGV can switch between driving modes and achieve high-precision positioning within ±5 mm, confirming the feasibility of using mechanical solutions for industrial positioning applications without costly electronic control systems.

In this study, we investigate the accuracy of four-node tetrahedral elements with drilling and strain degrees of freedom (GNTet4) for nearly incompressible materials. GNTet4 is a one of the generalized finite element method approximation. Three types of GNTet4 are introduced by applying approximation polynomials of the Taylor expansion. First, we reveal the extra degrees of freedom constraints without the zero-energy modes of each GNTet4 through eigenvalue analysis. Next, the displacement accuracy of each GNTet4 is evaluated by analyzing a cantilever beam. The results shows that GNTet4, which approximates the third-order Taylor expansion (GNTet4-3rd), is almost identical to a 20-node tetrahedral element. Furthermore, a plane-strain compression test is performed to investigate the analytical accuracy of each GNTet4 for nearly incompressible materials. To analyze nearly incompressible materials with high accuracy, selective reduced integration (SRI) and third-order Taylor expansion must be applied to GNTet4 (GNTet4-3rd with SRI). Incidentally, the analysis accuracy of GNTet4-3rd with SRI is the same as or higher than that of the 10-node tetrahedral element (FEM-Tet10). Furthermore, the GNT4-3rd with SRI, which possess the nodal point at the element vertex only, suppressed the nodal oscillation. Thus, in nearly incompressible materials, to obtain the same analysis accuracy as that of FEM-Tet10, the four-node tetrahedral element must apply the displacement function of the fourth order and the SRI.

With the further expansion of the Shinkansen network to northern region, sufficient low-temperature fluidity is required for axle-box oil of Shinkansen trains. Axle-box oil with excellent low-temperature performance has been developed in the past, however, it has not been put into practical use because of the maintenance problem caused by reddening when it is exposed to ultraviolet rays. Therefore, we have newly developed axle-box oils that are less prone to reddening and exhibit improved low-temperature performance compared with the current oil. The properties and performance of the prototype oils were evaluated in laboratory tests. The prototype oils exhibited improved low-temperature fluidity and did not redden under ultraviolet irradiation. The thermal stability and lubricating performance of the prototype oils was no less than those of the current oil. In addition, the durability tests using actual-size axle-box bearings were conducted for the more promising candidate of the prototypes. According to the test results, the durability of the prototype oil for 800,000 km use was confirmed because no abnormality was found from the results of the inspection of oils and bearings in between and after the test.

With new services provided by railway companies and changes in lifestyles, passengers doing tasks while traveling on Shinkansen and other trains are increasing. However, the conventional method of providing information to passengers is through voice announcements and LCD monitors in the train, and when working remotely while participating in an online meeting in a train, vision and hearing are used at the same time. Passengers performing such tasks must temporarily stop their visual or auditory tasks in order to obtain such information. Therefore, in this research, the purpose is to obtain information sent to passengers within the railway vehicle without interrupting visual tasks such as using a laptop, which passengers are performing inside the railway vehicle by utilizing the characteristics of human visual perception, especially the characteristics of the effective field of view. Subjective evaluation, eye movement, task performance, and other indicators were measured for 15 experiment participants when information was presented using the HMI proposed in this study. From the analysis results of experimental conditions, subjective evaluation values, and behavioral evaluation values, we found that experiment participants recognize a pictogram with little psychological effect, and 61% of them do not have a movement of gaze point.

Single-link used in rolling stock are an important component that connects the bogie to the car body. They trail and brake the car body according to the acceleration and deceleration of the bogie. The single-link buffer rubber used at both ends of the single-link is subjected to the high impact loads during bogie acceleration and deceleration, For this reason, the single-link buffer rubber is suitable for vibration isolation in railway vehicles, as it can withstand the high loads frequently applied to the vibration isolating rubber for rolling stock. The single-link buffer rubbers need to be replaced more frequently than normal vibration isolating rubbers and are required to have a longer service life. On the other hand, in order to extend the service life of single-link buffer rubber, it is necessary to understand the deterioration state of single-link buffer rubber used in actual vehicles and to develop a reproduction method that can reproduce the state of new products. However, such a method has not yet been established. Therefore, at first, we investigated the deterioration of single-link buffer rubber used in actual vehicles. As a result, it found that, while the overall tendency of single-link buffer rubber is to harden, it tends to soften in certain directions. Based on the results of this investigation, we conducted a combined test of heat aging test to harden the rubber material and fatigue test to soften the rubber material on a new single-link rubber buffer. The results showed that it was possible to reproduce the softening tendency in certain directions observed in used products.