Environmentally friendly design is becoming one of the major concerns in product design due to the growing impact of global warming and the pursuit of carbon neutrality. The ‘Tsugite’, observed in historical buildings in Japan, is a traditional joinery technique designed to enable the replacement of worn parts to extend the life of temples and pagodas. It is an inherently sustainable technique. In this paper, a new joint design method, based on the concepts of the ‘Tsugite’, is proposed. This method aims to enable the replacement of parts for frame-structured automobiles. Weighted spectral clustering is selected to design the joint, as a characteristic of the minimum-cut of spectral clustering is suitable for guiding and designing matching surfaces of the ‘Tsugite’ joinery. To apply this method to more complexly shaped mechanical joints, a coordinate transformation based on the principal axes of the stress tensor is introduced. By selecting the shear stress in the plane defined by the two maximum principal axes of the stress tensor as weights for clustering, appropriate clustering results can be obtained. The boundaries of clusters provide good guidance for designers to design mechanical joints for frame structures.

This paper advocates promoting not only for material recycling through destructive dismantling but also for encouraging part and component reuse by disassembly to establish an environmentally friendly circular economy. Addressing the challenge of high disassembly costs impeding economic efficiency, an evaluation method considering economic feasibility is proposed. The concept of “Disassembly” Design Structure Matrix (DSM) is introduced as an integration of Product Architecture DSM and Process Architecture DSM. This approach aims to maximize the disassembly profits by subtracting the process costs from the removed value of parts while satisfying the constraints of the disassembly sequence. Through a case study of a coffee maker, the cost-effectiveness of reusing parts and components is examined, and a feasible disassembly order beneficial to a company is presented. Additionally, areas requiring essential design changes are identified to achieve an easy disassembly design. The Disassembly DSM framework not only provides insights into sustainable structure alternations but also serves as a guide to identify violations of the desired disassembly order that require design modifications. In this study, the cost-effectiveness of disassembly work is derived by using the proposed Disassembly DSM framework for a simplified coffee maker. It is also confirmed that this method is effective for engineering designers as it can highlight design modification points for the early removal of high value parts.

A method for both quality improvement and design efficiency is required to meet diversifying customer requirements and human resource development. Especially in the case of production approach with customization, such as in industrial equipment, a design method that can appropriately develop product architecture and evaluate the diversity of modules in advance is necessary to suppress customization. Currently, such evaluation is implicit, and technical transferability is also a challenge. This paper proposes a method that combines a bottom-up approach and a top-down approach. In the bottom-up approach, modularization is implemented through the clustering of the Design Structure Matrix (DSM) to restructure the modular structure of existing products. The top-down approach considers variation design strategy by incorporating the diversity of customer requirements into the diversity of modules. A case study of servo motors is demonstrated. It is confirmed that the bottom-up approach is useful for organizing design considerations and generating ideas during new development because the module structure can be visualized. Furthermore, it is confirmed that the variation design strategy derived from the top-down approach is similar to the empirical view in current models. These results show that the proposed method is promising for formalizing tacit knowledge and supporting standardization of the design process to achieve both quality improvement and design efficiency.

The aim of this study was to investigate the effects of visual and auditory warnings on mental workload (MWL) during driving to induce drivers’ attention to safe driving. Twelve students (6 males and 6 females) who had Japanese driver’s licenses participated in this study. A total of four types of warnings, two each of visual and auditory, were presented during driving with a driving simulator. The N-back task was taken as a secondary task simultaneously with the driving task to control the MWL. Four eye movement parameters (i.e., standard deviation of eye rotation angle, standard deviation of gaze angle, head movement sharing ratio, and blink frequency) were used to estimate MWL. The Mahalanobis distance of four eye movement parameters between the four warning conditions and reference condition (i.e., without warning and N-back task) was calculated to estimate the MWL and investigate the effect of waring. The results showed that estimated MWL after warning tended to decrease when estimated MWL at warning presentation was high. Conversely, estimated MWL after warning tended to increase when estimated MWL at warning presentation was low. Therefore, it is suggested that warning presentation when MWL is high can be expected to be effective in inducing attention to safe driving.

Novelty is essential to product design, and novel colors enhance product appeal. With regard to novelty in product design, Loewy proposed the MAYA principle, which states that acceptable novelty is a condition for attractive design. This principle is qualitative, based on empirical rules. Based on Berlyne’s arousal potential formulated in information-theoretic free energy, we propose a mathematical model of acceptability to novel colors. In this model, the Bayesian prior was approximated by a normal distribution of the color frequency of the real case of interest, and the Bayesian likelihood function was quantified from the probability density of the frequency of the presence of color names. Our analysis of the mathematical model led to two hypotheses: first, the tolerance for novelty expands as the variance of the Bayesian likelihood function in the model increases, and second, as the variance increases, the colors that reach the optimal arousal level are more novel. We tested these two hypotheses in subject experiments to validate the mathematical model. We obtained significant results supporting hypotheses under conditions where the effect of visibility degradation was small. Applying the model, we developed a suggestion system for novel colors. In the system, contour lines of the same arousal potential levels are drawn on the color coordinate space. By utilizing this system, it is expected to suggest attractive colors with acceptable novelty levels.

By appropriately determining each layer's refractive index and film thickness, optical multilayer films can control the light spectrum using the interference effect of light. Combining solar and thermal power generation is possible using a heliostat with an optical multi-layer film attached to a solar cell panel in a tower-concentrated solar power generation facility. This research aims to design a super multilayer film that can control wide-angle and wide-band wavelengths based on the spectral sensitivity characteristics of solar cells. It is formulated as an optimization problem that seeks the optimum values of parameters such as the reflection center wavelength of one structural unit, the number of layers, and the incident angle. Design results for the case where the super multilayer film is attached to the back surface of the cover glass of the solar cell are reported.

This study investigated the remanufacturing process of automotive air conditioning compressors, starters, and alternators in Japan, and modeled the remanufacturing process using a functional modeling approach. By studying and observing the inputs and outputs of each remanufacturing process, we collected the data necessary for life cycle assessment and calculated the amount of greenhouse gas (GHG) emissions generated by each process and the associated costs. In addition, by estimating the GHG emissions generated during the manufacture of new parts and subtracting the emissions from the manufacture of remanufactured parts, it was determined that the use of remanufactured parts would reduce the expected GHG emissions by approximately 42-85%. In addition, by identifying the processes that account for a high percentage of the remanufacturing process, it was found that the process of manufacturing repair parts to replace worn parts accounted for the largest percentage. In terms of costs, it was found that in addition to the manufacturing of replacement parts, the processes associated with cleaning are a high percentage of the remanufacturing process. To enhance the GHG reduction effect using remanufactured parts, it was clarified that it would be effective to reduce both the number of replacement parts and cleaning by having the original manufacturer and the remanufacturer cooperate, share information on parts to be improved in terms of durability, and review the design of the parts. It was also found that efficient use of the equipment used in the cleaning, testing and drying processes would be effective in enhancing the GHG reduction effect.

This study proposes a method to support product architecture design considering the supply chain. Previous studies on product architecture design include methods to realize modularization and product family design based on the relationships among components. From the supply chain perspective, mathematical models and simulation models have been proposed to improve the supply chain of modularized products. However, there has been little research on design support that simultaneously considers product architecture and supply chain. In particular, there is little consideration given to the impact on the supply chain caused by the connection between components. To address this issue, this study proposes a design methodology for the simultaneous design of both product architecture and supply chain from the perspectives of economy, environment, quality, and transportation. This paper newly proposes an evaluation model that incorporates the production capacity of each supplier, the delivery capacity of each transportation mode, and the on-time delivery rate with consideration of above component connections. The proposed method supports the selection of an architecture and its supply chain by visualizing the characteristics, such as the trade-off between evaluation indicators depending on the degree of modularization. As a result of applying the proposed method to the architectural design of a laptop computer, we confirmed that the proposed method can suggest to the designer an appropriate architecture and its supply chain according to the number of products to be manufactured and their means of transportation.

Wire arc additive manufacturing has been receiving considerable attention as a cost-effective technology for its capability of producing near-net-shape parts directly from feedstock materials, and application to high cost and difficult-to-machine materials, such as titanium, is highly expected. On the other hand, titanium has high reactivity with oxygen or nitrogen at high temperature and this can be detrimental to its mechanical properties. In this study, commercially pure titanium was applied to wire arc additive manufacturing process by robotic metal inert gas welding, and some fundamental experiments with a newly proposed cylindrical type shielding gas nozzle were conducted. From such experimental results, it was shown that equipping the proposed gas shielding nozzle to welding robot could be effective to avoid contamination and characteristic degradation of additively manufactured titanium parts with complex geometry, even though the process is carried out under atmospheric condition.

For high-precision and high-speed control of robots, control systems are needed to be designed based on their dynamics models. The dynamics model requires identification of the dynamics parameters. However, due to un-modeled dynamics and noises, the conventional parameter identification methods such as LS (least square) method obtain only approximations whose optimality strongly depends on the control objectives. This paper proposes a method to identify values of the dynamics parameters suitable for use in control system design. In this method, the dynamics parameters are considered to be stochastic variables, and identified so that their variance is made small for large influence on control performance shaping its covariance to follow the desired one. By considering feedforward and feedback control system design with Linear quadratic regulator, the desired covariance matrix is introduced. Experiments using a planar 3-link manipulator show that the proposed method identifies the appropriate parameters, and the designed controller achieves highly accurate positioning of the end-effector.

Personal care robots are assumed to be frequent contact with humans. Thus, the limitation of mechanical inputs should be clarified for the development of safety standards on human-personal care robot interactions. In our previous studies, in vivo impact tests has been conducted using anesthetized pigs in order to obtain the injury resistance threshold caused by human-robot interactions. The impact points in this tests were selected the porcine chest and extremities. As a result, the bleeding threshold value of the porcine extremities was lower than that of the chest. However, the bleeding threshold of the porcine extremities has not been clarified yet. In this study, to investigate the threshold value for bleeding of the porcine extremities, we performed in vivo impact tests under the low impact energy conditions. Moreover, in vivo impact tests were simulated using a finite element model at the part of porcine thigh based on CT images to identify the tissue-level injury resistance evaluation index and the threshold value for bleeding. As a result, when the maximum stress based on the maximum impact force and contact area was used as the injury resistance evaluation index, the injury resistance threshold value for bleeding was 1.16 MPa in the in vivo impact test. The part of first principal stress concentration in the finite element analysis was in good agreement with the bleeding point obtained from in vivo impact tests. Moreover, when the first principal stress was used as the tissue-level injury resistance evaluation index, the threshold value for bleeding was 0.74～0.80 MPa.

In a long freight train, if some freight wagons derail away from the locomotive, there may be a delay in noticing the derailment. In such cases, there is a concern that the wagons may continue to run while derailed, causing significant damage to track components. Therefore, early detection of derailment is strongly required. On the other hand, it is difficult to apply the conventional derailment detection method with vibration acceleration sensors for passenger cars to freight wagons due to the specific characteristics of freight wagons. This is because freight wagons run in various conditions and on various tracks. Therefore, a derailment detection method with mechanical contact sensors has been investigated. The advantage of contact sensors is that derailment detection is easy to determine. Previous studies and findings have also indicated that specific parts of the bogies of freight wagons come in contact with other parts or rails during derailment. In this study, based on simulation results considering the results of previous studies, two suitable locations on the bogie were selected for the installation of the contact sensors. Furthermore, derailment tests were carried out on a real track by actually derailing a bogie with contact sensors installed and the detection performance was evaluated. The results showed that the contact sensors could detect the derailment immediately after it occurred.

Railway vehicles are required to reduce environmental impact with acceptable riding comfort. For this purpose, it is necessary to satisfy the conflicting issues of weight reduction and maintaining proper stiffness. However, in order to find out acceptable structure, repetitive calculation with finite element analysis is required because of its large and complex structure with thousands of parts. Here, it is required to accelerate analysis and establish a method for solution space. In this report, we propose a method to find out solution space between weight and stiffness on a "double-skin structure" composed of aluminum hollow extrusions for railway. We focused on the first vertical bending modes of the structure as an index of riding comfort and evaluated the equivalent bending stiffness of the structure based on the maximum amount of deflection obtained by static finite element analysis. In order to find out the solution space, we took three steps in the report. First, based on factors that would contribute to considerable bending stiffness extracted based on past research cases and experience, the magnitude of the contribution was quantitatively obtained and extracted using the experimental design method. Next, for the extracted factors, the relationship between the structure mass and the equivalent bending stiffness was formulated. Finally, solution space was obtained by inputting numerical values into the design factors within a practical range using the Monte Carlo method. As a result, it is concluded that proposed method brings solution spaces.

The moving block system provided by CBTC increases train operation frequency and improves facilities management efficiency compared to the fixed block system. Trains controlled by CBTC need to have onboard functions to estimate their locations. One method for location estimation involves integrating the measured translational velocity of the trains based on the angular velocity of the wheelset. However, this method may introduce errors in measuring the traveling distance because the angular velocity of the wheelset can be changed on curved tracks due to shifting contact points, longitudinal creepages, and other factors. To observe the phenomenon of angular velocity changes on curved tracks, experiments and simulations were conducted. The results of both experiments and simulations are similar, showing that the angular velocity of wheelsets changes on the curved track and the relative changes differ between the front and rear axles of the bogie. The mechanisms of the angular velocity changing is clarified, identifying three factors: arc length differences between high and low rails, changes in rolling radius on wheels, and longitudinal creepages. Additionally, the impacts of these factors are formulated, indicating that the relative change in angular velocity on curved tracks can be estimated by the sum of the formulated impact factors. Moreover, the visualization method for the mechanism determinating the wheelsets’ angular velocity is developed. This method helps to clarify the reasons for the different relative change observed between the front and rear axles in the bogie during experiments. Specifically, it suggests that the different directions of longitudinal creepages cause the different relative change in the wheelsets’ angular velocity.