The ionomer content in the catalyst layer is a crucial design factor that affects the performance of polymer electrolyte membrane fuel cells (PEMFCs). However, the optimal ionomer content can vary based on the surrounding humidity levels. This study systematically evaluated the influence of the ionomer-to-carbon (I/C) ratio (0.00, 0.55, and 0.91) on PEMFC performance under fully humidified (RH 100%) and low-humidity (RH 25%) conditions. Membrane-electrode assemblies (MEAs) were fabricated using a spray coating technique, and their electrochemical properties were analyzed through polarization curves and electrochemical impedance spectroscopy (EIS). Under RH 100%, the MEA with an I/C ratio of 0.55 achieved the highest peak power density of 519.8 mW/cm², indicating a successful balance between proton conductivity and gas transport. Conversely, under RH 25%, the best performance of 203.9 mW/cm² was observed at an I/C ratio of 0.91. This shift is attributed to improved water retention at higher ionomer content, which reduced membrane dehydration and lowered both ohmic and Faradaic resistances. These findings highlight the dual role of the ionomer in facilitating proton transport and managing water balance, emphasizing the necessity of optimizing the I/C ratio according to operating conditions for stable and high-performing PEMFC operation.

This paper addresses the issue of over-constrained assembly in mechanical designs using hole-pin patterns. When two hole-pin pairs are used, they can cause interference between components, leading to assembly failures. To mitigate this, designers often enlarge holes relative to pins to have a large float. However, when functional requirements do not permit significant float, field design engineers tend to add more assembly features, hoping them to mutually limit the float allowed by others. This numerical study employed two commercial tolerance analysis programs to demonstrate that these design changes could not sufficiently reduce float to justify added costs. Instead, this paper proposed an exactly-constrained design by replacing one of the holes with an elongated hole. Numerical analysis showed that this approach significantly reduced float compared to current design practices. This paper logically explains why this must be the case. It is hoped that this study contributes to the advancement of mechanical assembly design practices by adopting the exact constraint concep.

In this paper, we introduce a recently built screwing robotic system for the bolt assembly of elastic steel plates. The screwing robotic system consists of two vision cameras (having narrow and wide fields of view), a collaborative robot with a 10 kg payload, and a motorized screw drill with a pneumatic bolt supplier. Due to the elasticity of the steel plates, they tend to statically deform and dynamically vibrate during tasks under the conventional setting of automatic screwing, often resulting in screw failures. Thus, we designed a compliant connector device to be attached between the robot end-effector and screw drill that can absorb vibration and shock during the bolt assembly to improve the screwing quality and success rate of the bolt assembly. Upon adopting this screwing robotic system with the compliant connector, the success rate of the bolt assembly was improved from 56% to 100%.

In this study, the effects of repetition of assembly and disassembly of polymer electrolyte membrane fuel cells on electrochemical performance were systematically investigated. Additionally, the effects of additional activation on polymer electrolyte membrane fuel cells were evaluated. All fuel cells were measured every three days. For the disassembled polymer electrolyte membrane fuel cells, membrane electrode assemblies were stored in a vacuum desiccator. For the maintained assembly, fuel cells were stored at room temperature. The performance and electrochemical characteristics of the fuel cell were analyzed by electrochemical impedance spectroscopy. As a result, the addition of activation to maintained assembly fuel cells showed the best performance among fuel cells with other assembly and activation conditions. Repetition of assembly and disassembly, as well as insufficient activation, caused degradation of the performance of fuel cells.

In this study, the electrochemical characteristics of fuel cell were evaluated after applying a compressive load to the activation area of membrane electrode assembly (MEA) in polymer electrolyte membrane fuel cells. The effects of the pressed area under the compressive load were systematically investigated using polarization curves and electrochemical impedance spectroscopies (EIS) of the fuel cell. Interestingly, the performance of the fuel cell was improved as the pressed area of the MEA was increased from 25.2% to 100% of the active area. In addition, the increased pressed area led to a decrease in the ohmic resistance and the activation resistance of fuel cells.

The manufacturing industry is increasingly demanding flexible manufacturing and existing manufacturing methods with fixed equipment do not meet this requirement. The free spot assembly system is an ultra-flexible method that responds to this demand, enabling spatiotemporal free assembly by conveying all necessary resources with automated guided vehicles (AGVs). Although some studies have proposed free spot assembly, free spot assembly feasibility for assembling heavy objects, such as machine tools, by aligning them at high precision has not been verified. Work hour shifts, differences in worker skill levels, and cooperative work with robots have also not been considered in free spot assembly scheduling. This paper presents elemental technologies for realizing a free spot assembly system, with a scheduling method where a genetic algorithm is supported by dispatching rules with six genes. The computational results reveal the effectiveness of the proposed algorithm.

In the scheduling of assembly lines with human-robot collaboration, variations in workload caused by differences in the available working hours of workers and robots must be minimized. A scheduling method that considers buffers shared by automated guided vehicles and cooperative assembly by multiple workers is proposed herein. In particular, cooperative work requires an assembly schedule that minimizes the make span and satisfies the delivery date, while accounting for the possibility of work partitioning, the number of workers, as well as their available time slots and skills. Hence, it is difficult to obtain an exact optimal solution within a reasonable computation time using existing methods such as mathematical programming. Heuristic or metaheuristic approaches are effective for solving this problem. However, these approaches are not suitable for cooperative assembly by multiple workers. Therefore, a genetic algorithm supported by dispatching rules with four genes is proposed. Computational experiments are conducted based on multiple worker skills. The results showed that when the worker skills are the same, the genetic representation of the job name and part processing order is effective, whereas when the worker skills are different, the genetic representation of the cooperative process with the worker for each operation is effective.

In this paper, a multi-material non-assemble 3-DOF Force-Sensor was proposed and developed to improve the efficiency in the manufacturing. The PLA-Filament was used to produce the frame-structure and the elastic-deformation, and the conductive-PLA-filament, to produce a transducer. A dual-nozzle 3D-Printer was applied to produce the monolithic-structuretype force-sensor with the multi-materials simultaneously in single-manufacturing-process. The sensor was designed in a tripod-structure to detect the 3-DOF force-components in an external-force and a mechanical-interpretation was conducted on the elastic-deformation, which acts as a load-cell. The output model of a Wheatstone-bridge circuit-based transducer serving as a strain-gauge was also produced. A calibration-testing device, comprising a rotating stage, which turns with 2- DOF (θ, ϕ), was also developed to apply force in every direction. By conducting the calibration test, the relations between the input and output were computed in as a matrix and the resolution of the sensor was determined through the evaluation of linearity and stability deviations.

The assembly misalignment of a high maneuver precision guidance missile such as anti-air interceptor could have poor influence on the performance of the system and lead to fatal mission failure. Thus, several methods to minimize the assembly misalignment of missiles have been suggested, including assembly guiding tools and measuring devices. However, previously suggested solutions have disadvantages in versatility and cost. In this study, the low cost and universally applicable solution based on inclinometers for measuring assembly misalignment of a missile is introduced. The comparison between measurement data of the suggested system and a three-dimensional laser tracker for a missile assembly misalignment was conducted. The results show the suggested system can quantify a missile assembly misalignment with comparable precision and accuracy.

Automation of electronic connectors has been in demand, based on automation of assembly of electronic products. In this study, we propose a new classification of electronic connector, for grasping and assembling. We analyze characteristics of electrical connectors often used at actual industrial sites, from the perspective of the robot, not a person. As a result, it is appropriate to classify the grasp, according to the shape of the electric connector. For the assembly, we suggested that classification should be based on directions are different, because of interference of the electric wire and peripheral parts. We hope that this research will become a new basis, for electrical connector assembly.

This paper proposes a new improved methodology to assess reconfiguration manufacturing system (RMS) adaptability in small and medium manufacturing industries. The evaluation of scenarios and alternatives for a reconfigurable design in manufacturing systems requires efficient and convenient methodologies to confirm the comparative evaluation metrics of the assigned KPI. Customizable factors are extracted and mapped for the design structure matrix and the analytic hierarchy processes. Reconfiguration event information is visualized as bill of resource. Evaluation format of KPI choice is then suggested. The reconfiguration control manager is designed to extract and combine the objects and the resource library of the reconfigurable assembly module and line. This paper first proposes the improved evaluation modeling frame and format with the newly refined KPI for the assessment of reconfiguration adaptability. Second, it shows the applicable suitability through a partly designed domain at the real automotive components manufacturing and assembly factory. Finally, it discusses the issues related with the customization and case results by the suggested evaluation methods.