Journal of the Korean Society for Precision Engineering

Dynamic Characteristic-based Driving Performance Analysis of a Semi-active Suspension Wheel Module for Small Mobile Robots: Seoyeon Park, Sungjae Kim, Juhyun Pyo, Murim Kim, Jin-Ho Suh; J. Korean Soc. Precis. Eng. 2025;42(11):919-926.
Published online November 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.069

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This study details the development of a semi-active suspension wheel module for small mobile robots and assesses its dynamic characteristics under various driving conditions through simulation. The wheel module features a low-degree-of-freedom mechanical design and includes a semi-active damper to improve adaptability to different environments. To validate the simulation model, a prototype robot equipped with the wheel module was created, and obstacle-crossing experiments were conducted to measure vertical acceleration responses. The model was then refined based on these experimental results. By employing design of experiments and optimization techniques, the effective range of damping coefficients was estimated. Additionally, simulations were carried out at different speeds, payloads, and obstacle heights to identify optimal damping values and examine their trends. The results indicate that the proposed module significantly enhances driving stability and can serve as a foundation for future control strategies in robotic mobility systems.

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A Study on Numerical Thermal Design Techniques for High-power Propulsion Motors: Jaehun Choi, Chiwon Park, Heesung Park; J. Korean Soc. Precis. Eng. 2025;42(11):893-900.
Published online November 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.036

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Propulsion motors are vital components in marine propulsion systems and industrial machinery, where high torque and operational reliability are paramount. During operation, high-power propulsion motors generate considerable heat, which can adversely affect efficiency, durability, and stability. Therefore, an effective thermal management system is necessary to maintain optimal performance and ensure long-term reliability. Cooling technologies, such as water jackets, are commonly employed to regulate temperature distribution, prevent localized overheating, and preserve insulation integrity under high-power conditions. This paper examines the cooling performance of water jackets for high-power propulsion motors through numerical analysis. We evaluated the effects of three different cooling pipe locations and varying coolant flow rates on thermal balance and cooling efficiency. Additionally, we analyzed temperature variations in the windings and key heat-generating components to determine if a specific cooling flow rate and pipe configuration can effectively keep the winding insulation (Class H) within its 180^oC limit. The findings of this study highlight the significance of optimized cooling system design and contribute to the development of efficient thermal management technologies, ultimately enhancing motor reliability, operational stability, and energy efficiency.

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Customized Current Control of a Linear Motor Motion Stage: Kyung Ho Yang, Hyeong-Joon Ahn; J. Korean Soc. Precis. Eng. 2024;41(11):875-880.
Published online November 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.085

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In the 4^th Industrial Revolution, advancements in semiconductor technology demand high performance, efficiency, and precision, highlighting the importance of high-speed and ultra-precise motion stages. To improve positioning performance of a motion stage, robust torque generation by current controllers alongside position control is crucial. This paper explored a custom current control for linear motor motion stages. We built a linear motor motion stage with a 560 mm stroke, 5 m/s speed, and 280 N continuous thrust supported by air bearings and equipped with a passive reaction force compensation. Custom user code for position and current controls of PowerPMAC motion controller was developed for the motion stage. The position control code included frequency domain system identification, disturbance observer, and repetitive learning control while the current control code featured vector or d/q-axis current controllers and disturbance observer. We developed a current control tuning GUI to adjust the current control gain by injecting an excitation signal into the motion controller and measuring the frequency response of the open-loop transfer function. Experimental results confirmed the effectiveness of the custom current controller for evaluating static and dynamic performance.

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Development of a Compound Planetary Gearbox for Robot and Performance Evaluation Using Dynamometer: Jae Hong Lee, Jun Ki Hong, Soo Ho Woo, Soon Geul Lee; J. Korean Soc. Precis. Eng. 2024;41(3):163-168.
Published online March 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.100

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Gearboxes used in the drivetrain of intelligent robots are key mechanical components that play a significant role in determining the performance of modern robotic systems. Gearboxes employing the planetary gear mechanism, known to achieve a wide range of reduction ratios while remaining relatively cost-effective, have recently been adopted in robot drivetrains. In this paper, we utilize domestic technology to fabricate a gearbox using a compound planetary gear mechanism and conduct an evaluation of eight performance aspects of the developed gearbox through the fabrication of a dynamometer and a jig. The dynamometer comprised of the gearbox, input motor, input-output torque sensors, and a powder brake. By driving the input motor and applying braking force with the powder brake, we compare input torque sensor values with output torque sensor values to derive results. A test jig is created, consisting of an input motor, gearbox, and encoder sensor, for the measurement of inverse operation characteristics and backlash. By conducting a performance evaluation of the developed high-strength, high-reduction-ratio compact planetary gearbox, we validate the potential of the testing system and extend the scope of domestic gearbox technology development.

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Three-dimensional reconstruction of gearbox from multi-view point clouds with surface feature parfameter measurement method
Jian Chen, Zhijia Zhang, Guanghui Liu, Dejian Li, Qiushuang Li
Engineering Research Express.2025; 7(4): 045253. CrossRef

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Multi-criteria Decision Making of the Optimal Micromachining Process Using Fuzzy AHP-TOPSIS: Seong-Gu Kang, Jihong Hwang; J. Korean Soc. Precis. Eng. 2023;40(8):617-624.
Published online August 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.021

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There are various micromachining processes available for manufacturing highly integrated and precise parts, each having its own characteristics and limitations. The degree to which micromachining processes meet the requirements depends on characteristics of parts that are different, making it difficult to determine the most appropriate process. In this context, the present study presents an algorithm for determining the optimal micromachining process by applying the Fuzzy AHP-TOPSIS technique frequently used for multi-criteria decision-making. Fuzzy AHP was employed for calculating weights of requirements for a given part. Fuzzy TOPSIS was employed for determining ranks of candidate processes based on weights of requirements and evaluation of processes. Fuzzy logic was applied to handle ambiguous and inaccurate information encountered in evaluating the relative importance of requirements and performances of processes. The case study in which the optimal process for micro-hole drilling of a fuel injection nozzle was determined showed that the proposed method was effective. It could be extended to micromachining of various shapes.

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Cutting of Chemically Strengthened Glass Using the Combination of Electrochemical Discharge and Grinding Processes
Jonghwan Kim, Jihong Hwang
Journal of the Korean Society for Precision Engineering.2024; 41(12): 957. CrossRef

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A Study on the Smart Design and Cooling Performance of Electric Vehicle Motor Using Metal-Hybrid Materials: Sung-Hwan Bang, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(8):595-603.
Published online August 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.039

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The aim of this study is to numerically investigate the cooling performance of the electric vehicle motor depending on the attachment of the heat sink and materials to the cooling channel. The research focused on the numerical comparison of forced convective heat transfer coefficients with case 1 (Heat Sink-None, Cooling Channel-Al), case 2 (Heat Sink-None, Cooling Channel-Metal Hybrid Material), case 3 (Heat Sink-4EA, Cooling Channel-Al), and case 4 (Heat Sink-6EA, Cooling Channel-Al). To compare the cooling performance for novel design of the smart cooling system, selected local positions for various temperature distributions were marked on the coil surface. Normalized local Nusselt number of the cooling area at the normalized width position indicated that cooling performance of case 1 was on an average 8.05, 0.57, and 5.85% lower than that of cases 2, 3, and 4, respectively.

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Vehicle-motion-based Front Wheel Steer Angle Estimation for Steer-by-Wire System Fault Tolerance
Seungyong Choi, Wanki Cho, Seung-Han You
Journal of the Korean Society for Precision Engineering.2024; 41(5): 347. CrossRef

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Weld Strength of Longitudinal and Longitudinal-Torsional Mode Horns in Ultrasonic Metal Welding: Dong Sam Park, Jin Bom Kim, Ji Won Seo; J. Korean Soc. Precis. Eng. 2021;38(8):619-626.
Published online August 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.030

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The ultrasonic metal welding technique has been widely used because of the need to weld different materials for meeting high quality performance requirements. The key part in this type of welding is the horn, which plays an important role in the weld quality. Longitudinal vibration has so far been the most popular vibration mode for ultrasonic horns, but the longitudinal mode coupled with torsional mode is gaining a lot of attention these days owing to its better performance compared to the pure longitudinal mode. Although there are many studies on the performance of these two mode horns, comparative studies based on the performance of these two modes, particularly in ultrasonic metal welding, are very rare. This study focuses on the welding performance comparison of these two horns with 20 kHz resonant frequency. Experimental results show that the performance of the longitudinal-torsional horn is better than that of the longitudinal horn in terms of welding strength.

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Trade-off between dynamic recrystallization and material ejection during ultrasonic welding of cylindrical cell current collector plate and positive terminal
Mounarik Mondal, Savyasachi Nellikode, Seong-Beom Park, Jun Mitsuyuki, Soomin Lee, Do-Hyeong Kim, Yeong-Do Park
The International Journal of Advanced Manufacturing Technology.2025; 137(11-12): 5837. CrossRef
The application of ultrasound in Joining: Principles, processes and properties
Zongkai Fan, Keran Bai, Chao Chen
Journal of Manufacturing Processes.2023; 101: 269. CrossRef

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Performance Analysis of the Solid Rocket Propulsion System Using Solid Modeling and Level Set Method: Kyung Moo Kim, Doo Hee Han, Min Kyum Kim; J. Korean Soc. Precis. Eng. 2021;38(7):501-511.
Published online July 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.033

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The performance prediction and grain burn-back analysis of rocket motor are important steps in the designing of a solid propellant rocket motor. The grain burn-back analysis of the solid grain identifies the burning surface area at each burning step in order to predict pressure-time history of the rocket motor. In this study, the shape of propellant grains was conveniently designed based on a solid modeling program of conventional purpose and the internal ballistics analysis was performed using a Matlab code which was developed to analyze the grain burn-back for this shape model. Upon carrying several analyses for rocket motors, it was confirmed that the developed code is suitable and useful.

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Smart Cooling System Design for Augmentation of Cooling Performance of Electric Vehicle Driving Motor Utilizing Cooling Channel Fin: Si-Mok Park, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(6):427-439.
Published online June 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.020

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This research is to investigate the cooling performance of the motor in the electric vehicle depending on the cooling channel fin. The research focused on numerical study of the temperature of coil and cooling channel and the heat transfer coefficients to find a optimum design shape with high cooling performance at three different cases. To compare the convective cooling performance of the three cooling channels, local position (R) are displayed on the surface of the coils with a large temperature deviation. This research was performed on forced convection and was numerically analyzed by FLUENT V20.2. Owing to forced convection by the same mass flow, the average cooling channel velocity in Case 3 was 17.4% faster than Case 1 and 8.6% faster than Case 2. Out of the three cases, the highest heat transfer coefficient was found in the cooling channel and coil of Case 3, which had two cooling fins. The coil maximum temperature of Case 3 with 2 cooling fins was 4.7% lower than Case 1 without cooling fins and 1.7% lower than Case 2 with 1 cooling fin. Ultimately, Case 3 with two cooling fins provided the best cooling performance and improved driving motor performance for motor durability.

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Thermal management strategies and power ratings of electric vehicle motors
Jaya Antony Perinba Selvin Raj, Lazarus Godson Asirvatham, Appadurai Anitha Angeline, Stephen Manova, Bairi Levi Rakshith, Jefferson Raja Bose, Omid Mahian, Somchai Wongwises
Renewable and Sustainable Energy Reviews.2024; 189: 113874. CrossRef

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A Study on Cooling Performance of Electric Vehicle Motor for Different Cooling Channel Shapes: Si-Mok Park, Seong-Hwan Bang, Min-Gi Chu, Ji-Hun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(6):417-425.
Published online June 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.019

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This research investigated the cooling performance of the motor in electric vehicle depending on the shape of the cooling channel. The research, conducted numerically by FLUENT V20.1, focused on the numerical study of heat transfer coefficients to find an optimum design shape with high cooling performance. To compare the cooling performance, the temperatures in the coil and cooling channel were analyzed. As a result of forced convection, the average cooling channel velocity of Case 2 was 38% faster than Model N and 34% faster than Case 1. The maximum temperature of the cooling channel of Case 2 was 8.7% lower than Model N and 5.6% lower than Case 1. The minimum temperature of the coil of Case 2 was 2.7% lower than Model N and 4.3% lower than Case 1. The maximum temperature of the coil of Case 2 was 4.6% lower than Model N and 2.9% lower than Case 1. Ultimately, cooling channel of Case 2 showed the best cooling performance and improved driving performance for motor durability.

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Development of a novel electro-mechanical brake motor thermal management system for nonuniform heating under extreme thermal conditions
Piljun Park, Hongseok Choi, Sangwook Lee, Sunoh Jeong, Hoseong Lee
Energy Conversion and Management.2025; 325: 119406. CrossRef

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Numerical Investigation on the Cooling Performance of Energy Storage System according to Type of HVAC: Hwabhin Kwon, Heesung Park; J. Korean Soc. Precis. Eng. 2020;37(9):685-690.
Published online September 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.027

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In this paper, we analyze the cooling performance according to the HVAC types installed in the energy storage system (ESS). Batteries in ESS have the disadvantages of decomposition and catching fire at high temperatures, so it is important to control the temperature. For the purpose of cooling the batteries in ESS, we designed the cooling systems with stand and ceiling type HVAC. Both the cooling systems for ESS are analyzed numerically for the comparison of cooling performance. The heat dissipation of the battery is 1979.3 W/m3 on 1 C-Rate discharge, and the cooling flow rate and temperature are 6.375 kg/s and 17℃, respectively. The maximum temperature of batteries with stand and ceiling type cooling systems are calculated to be 65.85 and 60.5℃, respectively. In conclusion, cooling systems with ceiling type HVAC are more efficient than cooling systems with stand type HVAC.

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Design of a 7-DOF Upper-Limb Exoskeleton Robot based on Performance Index: Byeong Kyu Lee, Chang Soo Han; J. Korean Soc. Precis. Eng. 2020;37(9):653-658.
Published online September 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.022

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For the teleoperation of dual-arm robots with various tasks, the existence of a controller with a high degree of freedom is indispensable. Especially when precise work is required, additional information such as force feedback is very helpful for the operator. In transmitting such force information, a control device of exoskeleton-type with many points of contact with the human body can be one of the solutions. This paper proposes an optimal design method for the 7 degrees of freedom (DOF) exoskeleton systems. The proposed method optimizes the kinematic parameters by using kinematic performance indices related to the dexterity of the human and exoskeleton system. The manipulability ellipsoid is a representative index that can confirm the dexterity of the robot. In this study, we derived the objective function considering the human body model and then optimized it using a genetic algorithm. Unlike other HRI (Human-Robot Interaction) systems, exoskeleton robots share the end-effector as well as the base of the robot with the wearer. Therefore, it is hypothesized that the proposed performance index will be highly suitable for exoskeleton systems.

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Development of a Realistic Simulator for Driving Education of a Disaster-Responding Special Purpose Machinery
Hyo-Gon Kim, Jung-Woo Park, Hyo-Jun Lee, Sung-Ho Park, Young-Ho Choi, Byeong-Kyu Lee, Jin-Ho Suh
Journal of Power System Engineering.2021; 25(2): 86. CrossRef

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Characteristic Evaluation of the Measurement Temperature in a Semi-Opened Furnace for Performance Evaluation of Medium/Low Temperature Ceramic Fuel Cells: Sanghoon Ji; J. Korean Soc. Precis. Eng. 2020;37(2):157-161.
Published online February 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.143

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The measurement temperature characteristics in a semi-opened furnace used for performance evaluation of medium/low temperature ceramic fuel cells were experimentally examined. Temperature measurement positions were classified into two cases with the attached condition (A thermocouple is in contact with fuel cell surface) and the floated condition (A thermocouple is apart from the fuel cell surface). Compared to the floated condition, the attached condition exhibits the characteristics of higher measurement temperature and better temperature stability. When the measurement temperature of the attached and floated conditions based on calibrated temperatures were controlled to 250°C, the peak power density of ceramic fuel cells with yttrium-doped barium zirconate thin-film electrolyte was measured at approximately 50% smaller for the attached condition comparison with the floated condition. Comparison of the ohmic area specific resistance for ceramic fuel cells with yttria-stabilized zirconate substrate electrolyte showed that, for the performance evaluation reliability, the attached condition is more appropriate than the floated condition.

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Automation Control System for Servo Prep Column of High-Performance Liquid Chromatography Based on Fuzzy Inference Control: Oyoung Kwon, Hyung Suk Park, Seok Geun Oh, Daehie Hong; J. Korean Soc. Precis. Eng. 2019;36(12):1135-1140.
Published online December 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.12.1135

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This paper describes a control system for the servo prep column of High-Performance Liquid Chromatography (HPLC) based on fuzzy inference control. The key technology in pharmaceutical and biotechnology industries is refining performance and efforts to reduce costs by purifying target compounds with high purity at high yield while maintaining target compounds, is the major focus of new product development. Among the many refinement techniques, the most popular chromatographic methods require a column that can charge the resin with excellent performance and reproducibility. However, the present HPLC prep column has a hydraulic for control moving stopper and compressed chemical compound. It always causes irregular performances of the column. This paper presents automation control with a servo motor that prevents slurry issues and improves efficiency of the prep column reproducibility and provides easy automation. As an automation method, cortex-m4 as an embedded processor and operating system with LabVIEW, are used to control the HPLC system. To generate the heuristic data for the fuzzy inference control, experiments are conducted to identify correlation between data such as pressure sensor and motor speed. The result will improve performance of the servo prep column of HPLC for automation control based on fuzzy inference control.

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A Study on the Mechanical Characteristic of Elastomeric O-ring Compressed and Highly Pressurized: Jun bok Ko, Seong Su Kim, Young Soo Park, So Dam Yi, Ki Bong Baek, Suhk hoon Suh; J. Korean Soc. Precis. Eng. 2019;36(8):721-728.
Published online August 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.8.721

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Elastomeric O-ring seals are widely used in static and dynamic applications due to their excellent sealing capacity, and availability in various costs and sizes. One of the critical applications of O-ring seals is solid rocket motor joint seal. In this, the operating hot gas must be sealed during the combustion time. In this study, we analyzed the behavior of O-ring compressed and highly pressurized by using the finite element method. The numerical analysis technique was verified through the comparison of analytical model and FE results. By using the verified FE method, the contact stress profiles at the sealing surfaces were investigated. It was found out that the contact stress profiles and deformation behaviors of the Oring are affected by friction coefficient, extrusion gap and stress relaxation considerably.

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Experimental and numerical evaluation of a rubber seal in a vacuum suction pad for an automatic mooring system
Yeonhong Son, Taehyun Lee, Jung Yup Kim, Hwasup Jang, Jongjik Lee, Youngki Kim, Songkil Kim, Yongjin Kim
Marine Structures.2024; 94: 103573. CrossRef
A Study on Sealing Performance Analysis for Electric Vehicle Coolant Control Hub Modules System
Kim Gisu, Jeongsun Lee, Dongchul Kim, Myeongeui Song, Cho Wooyeon
Transaction of the Korean Society of Automotive Engineers.2023; 31(3): 227. CrossRef
Structural Analysis and Experimental Study on the Spherical Seal of a Subsea Connector Based on a Non-Standard O-Ring Seal
Dong Liu, Feihong Yun, Kefeng Jiao, Liquan Wang, Zheping Yan, Peng Jia, Xiangyu Wang, Weifeng Liu, Xiaoquan Hao, Xiujun Xu
Journal of Marine Science and Engineering.2022; 10(3): 404. CrossRef