This study introduces a wire-spring based planar gravity compensation mechanism and evaluates its performance through both analysis and experiments. The mechanism features three pulleys, one spring, and one wire, all arranged in a planar configuration for compact installation within a robotic arm. A linear approximation of the target gravitational torque was derived using the least-squares method, allowing for the determination of spring stiffness and initial tension. Experimental results indicated that the proposed mechanism reduced the maximum torque by approximately 63%. However, the measured slope was gentler than the theoretical model due to friction losses. Additional tests that varied spring stiffness (k) and initial wire tension (A) confirmed that k primarily influences the slope of the compensation torque, while A affects its intercept. This finding suggests that compensation performance can be tailored to specific requirements by adjusting these parameters. The study successfully demonstrates a compact and lightweight mechanism and experimentally validates its tunability through design adjustments. Future research will focus on reducing friction, extending the mechanism to multi-degree-of-freedom systems, and validating performance under dynamic conditions for applications in collaborative and medical robots.

The semiconductor industry is experiencing significant growth in production scale and investment, driven by rising demand for generative AI, high-performance computing (HPC), high-bandwidth memory (HBM), and high-performance/high-density chips. As a result, precision inspection and yield management at the wafer stage have become critical challenges. Probe cards, essential for verifying a chip's electrical performance, play a vital role in yield management. However, during repetitive inspection processes, probe cards absorb heat from the underlying chuck, leading to probe tip-pad alignment errors that degrade contact reliability and measurement accuracy. This situation necessitates a quantitative evaluation system based on thermo-structural coupled analysis. Additionally, the modeling process for multiple interposers and interposer housings, along with the preprocessing of contact conditions, adds complexity due to the increasing number of contact surfaces. This complexity can result in convergence issues and reduced accuracy. To address these challenges, this study employs Ansys Parametric Design Language (APDL) to enhance interposer and housing modeling, as well as contact problem resolution. It introduces a novel meshing method that positions nodes at target coordinates using point clouds, providing an effective analysis approach applicable to large, high-density probe cards and thermo-structural problems involving numerous contacts.

With rapid growth of the global electric vehicle market, interest in the development of secondary batteries such as lithium batteries is also increasing. Core functional parts of secondary batteries are known to determine the performance of these batteries. Micro cracks, scratches, and markings that may occur during the manufacturing process must be checked in advance. As part of developing an automated inspection system based on machine vision, this study optimized the design of a linear feeder exposed to an environment with a specific operating frequency continuously to transfer parts at a constant supply speed. Resonance can occur when the natural frequency and the operating frequency of the linear feeder are within a similar range. It can negatively affect stable supply and the process of finding good or defective products during subsequent vision tests. In this study, vibration characteristics of the linear feeder were analyzed using mode analysis, frequency response analysis, and finite element analysis. An optimal design plan was derived based on this. After evaluating effects on vibration characteristics for structures in which vibrations or periodic loads such as mass and rails were continuously applied, the shape of the optimal linear feeder was presented using RSM.

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.

This study focuses on preventing folding defects in the forging process of parachute harness parts. Through three- dimensional finite element analysis, it was determined that folding defects arise from uneven metal flow and timing differences in the filling of various regions. To address these issues, a preform die was designed and evaluated using multi-stage forging simulations. The results indicated that the preform die facilitated uniform metal flow, preventing folding defects and ensuring consistent filling across all key areas. To verify the simulation results, surface and cross-sectional metal flow analyses were conducted. Additionally, the preform die reduced the maximum die load, which is expected to extend die lifespan and improve overall process efficiency. These findings demonstrate that precise control of metal flow and the application of a preform die can significantly enhance the quality and durability of forged components, providing valuable insights for improving forging processes across various industries

This study aims to optimize the process conditions for high-density polyethylene (HDPE) additive manufacturing through a systematic analysis of key variables, including material selection, layer height, feed rate, melting temperature, and bed temperature. By exercising precise control over these variables, optimal conditions were established, which included a melting temperature of 240oC, a welding speed of 150 cm/min, and a material throughput of 5.66 kg/h. Furthermore, the process was refined by implementing a zig-zag layering method, which significantly improved the stability, bonding strength, and overall mechanical properties of the final HDPE products. The effects of these optimized process conditions were assessed through a series of mechanical tests, such as tensile tests, impact tests, and heat deflection temperature (HDT) tests. As a result, the defined process conditions yielded excellent mechanical performance, achieving a tensile strength of 21.15 MPa, an impact strength of 320 J/m, and an HDT of 93oC. Overall, this study illustrates the enhancement of HDPE additive manufacturing quality through the optimization of process conditions. The strategic implementation of these optimized variables, along with advanced extrusion module design, demonstrates the potential for producing high-quality and cost-effective HDPE products, thereby underscoring their enhanced marketability and performance potential.

Safety accidents related to falls and collisions involving strollers occur every year. To address this issue, an automatic brake system has been developed and tested for strollers. Previous systems were only functionally verified and did not confirm structural safety until the brakes were activated and came to a stop. Given that this system is a safety-critical device, a prototype was manufactured and tested to ensure the device's safety during brake operation. Additionally, structural analysis was conducted using the collected data to identify potential vulnerabilities.

In the field of construction automation, significant research efforts continue to focus on replacing human labor; however, the varied and dynamic nature of construction sites still requires human intervention. The high task intensity in construction sites, particularly in lifting heavy materials, frequently results in musculoskeletal disorders among workers. To address this issue, this paper proposes a lifting device to replace manual material transportation through an opening between floors. The lift is designed with a gear-constrained double parallelogram mechanism to enable straight vertical movement. Moreover, a crank-rocker mechanism is incorporated to improve efficiency in repetitive tasks, reduce the required driving torque, and simplify control complexity. Additionally, this study introduces a passive gravity compensation mechanism that employs springs and cables, tailored to the lifting process, to enhance payload capacity and stabilize actuation. Through the integration of these mechanisms, the necessary motor capacity and control costs are significantly reduced. The effectiveness of the device is validated by actuation experiments with a fabricated prototype.

This study proposed a method for simultaneously reducing mass imbalance and vibration in gimbal systems utilizing a tuned mass damper (TMD) as a balancing weight. Finite element analysis (FEA) and experiments were used for testing the method. Mass imbalance in gimbal systems generally causes external disturbance torque. To reduce this, a balancing weight can be used. However, weight increase due to balancing weight causes resonance in the gimbal system, which generates bias error in the gyroscope sensor. This study demonstrated that both mass imbalance reduction and vibration reduction effects could be achieved by utilizing a TMD as a balancing weight. FEA results showed that the mass imbalance reduction effect of the gimbal was not affected by TMD. The magnitude of vibration response at the resonance point was reduced by about 98% with TMD. When a TMD was applied, the magnitude of the vibration response at the resonance point was reduced by 98% to the same level as that of the gimbal. Bias error of the gyroscope sensor was reduced by about 95% or more. These results show that a TMD is useful for effectively reducing mass imbalance and vibration in gimbal systems while improving gyroscope sensor performance.

In this study, polyacetal plates were machined with an indexable drill (Ø18mm) to measure the dimensional error of holes according to the cutting conditions and investigate the influencing factors to obtain precision holes. Cutting velocity, feed, and depth of cut were selected as experimental variables, analyzed using design of experiment, and optimal cutting conditions were investigated. Cutting velocity and feed were significant factors affecting hole accuracy, whereas depth of cut had little effect. The factor with the greatest influence on hole accuracy was cutting velocity, and the dimensional error of the holes tended to increase as the cutting velocity increased. Dimensional error tended to decrease as feed increased. In addition, the interaction effect between cutting velocity and feed and cutting velocity and depth of cut were significant. In this experiment, the optimal cutting velocity, feed, and depth of cut needed to minimize the dimensional error of holes were 100 m/min, 0.15 mm/rev, and 2 mm, respectively.

As advanced driver-assistance systems become more common in commercial vehicles, there is a growing need for evaluating safety of vehicles. Low platform target robot systems play a crucial role in this evaluation process as they can assess safety performances of autonomous vehicles. Driving stability of a target robot during real vehicle tests depends significantly on its suspension system. Therefore, developing an appropriate suspension device for the target robot is of utmost importance. This study aimed to improve driving stability by comparing two different suspension configurations: a single rocker and a double rocker, both incorporating a crank rocker mechanism. Initially, a two-dimensional model that met constraints of the suspension device was developed, followed by an analysis of reaction forces. Subsequently, an optimal design was determined using design of experiments principles based on parameters of a 2D model. The manufactured suspension system model based on the optimal design underwent multi-body dynamics simulation to evaluate driving stability. Comparative analysis of driving stability for both configurations was performed using MBD simulation, offering insights into the superior suspension design for the target robot.

This paper presents the development of a design optimization module for achieving the best performance of hydrostatic bearings. The design optimization module consists of two components: a bearing performance analysis module and an optimization module that utilizes optimization algorithms. Widely recognized global search methods, genetic algorithm (GA), and particle swarm optimization (PSO) algorithm, were employed as the optimization algorithms. The design optimization problem was defined for hydrostatic bearings. Optimization design processes were carried out to improve load capacity, stiffness, and flow rate. Subsequent experimental validation was conducted through the fabrication of a practical experimental setup. The design optimization model demonstrated superior performance compared to the initial model while satisfying design conditions and constraints. This confirms the practical applicability of the design optimization module developed in this study.

Urban air mobility (UAM) is rapidly growing as a new means of transportation. As a result, noise pollution is emerging as a new technical challenge. Therefore, the sawtooth-shaped biomimetic designs were incorporated on the trailing edge of the blade to reduce flow-induced noise. The biomimetic virtual design was analyzed using the CFD software, ANSYS FLUENT V20.2. Based on the steady-state RANS flow solution, the acoustic power was calculated using the broadband noise source model to evaluate acoustic radiation. Four different cases with cutting lengths of 3.1 mm, 3.7 mm, 4.3 mm, and 4.9 mm of blades were compared with the base model at the rotational blade speed of 6,000 RPM. The maximum acoustic power level of the biomimetic blades ranged from 37.24 dB to 39.88 dB, resulting in a 10% reduction compared to the original blade (42.02 dB). The novel design affected the blade area, which inevitably reduced the slight thrust performance. However, the thrust was reduced to approximately less than 5% compared with the base blade in case 1. The biomimetic blade reduced the thrust due to its aerodynamic characteristics. However, the design of a blade with an appropriate cutting length has a greater effect in reducing noise rather than thrust.