Journal of the Korean Society for Precision Engineering

Aerodynamic Flow Characteristics Inducing Centrifugal Compressor Noise Generation in High-speed Turbomachinery: Jihun Song, Chang Ho Son, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2025;42(9):763-770.
Published online September 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.088

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Centrifugal compressor is a device that converts kinetic energy to increase the air pressure. It rotates at a high speed of up to 200,000 RPM and directly affects aerodynamic noise. Various studies have already been conducted, but the direct calculation method of acoustics based on the unsteady solution is inefficient because it requires a lot of resources and time. Therefore, flow characteristics and numerical comparison according to various aerodynamic factors predicted as a cause of noise generation were analyzed in this study based on the steady solution. High-frequency noise was calculated locally near the asymmetric flow properties. Vortex and turbulent kinetic energy were generated at similar locations. Among static components, a large-sized vortex of 3.48×10⁷ s^-1 was distributed at the location where the rotational flow around the compressor wheel combined with the inlet suction flow. In addition, a locally high vortex of 8.16×10⁵ s^-1 was distributed around the balancing cutting configurations that cause asymmetric flow characteristics. Analysis of these factors and causes that directly affect noise can be efficiently improved in the pre-design stage. Therefore, the efficient design methodology for centrifugal compressors that considers both performance and noise is expected based on the results of this study.

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A Highway Secondary Accident Prevention System based on FFT Analysis of Vehicle Collision Sounds: Minki Jung, Young Shin Cho, Yongsik Ham, Joong Bae Kim; J. Korean Soc. Precis. Eng. 2025;42(9):749-756.
Published online September 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.037

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This study introduces a highway secondary accident prevention system that employs Fast Fourier Transform (FFT) analysis of vehicle collision sounds. The system is designed to identify abnormal acoustic patterns produced during collisions and skidding events, enabling faster and more accurate accident detection than traditional methods. When a crash is detected, visual warning signals are instantly sent to nearby vehicles using LED devices powered by a photovoltaic panel and an energy storage system (ESS). Experimental results showed 100% detection accuracy during independent playback of collision, skidding, and driving sounds, and 80% accuracy during simultaneous playback. These results confirm the system's ability to effectively differentiate accident-related sounds and deliver timely alerts. This research offers an innovative and environmentally sustainable approach to enhancing highway safety and reducing the societal and economic consequences of secondary accidents.

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Spectral Shaping for Pulse Quality Improvement in GHz-repetition-rate Electro-optic Comb Lasers: Junyeong Sung, Yeong Gyu Kim, Byungjoo Kim, Jiyeon Choi, Sanghoon Ahn, Geon Lim, Hyonkee Sohn, Dohyun Kim; J. Korean Soc. Precis. Eng. 2025;42(7):513-519.
Published online July 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.060

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Lasers are widely used in precision metrology, defense, and micromachining. The rise of GHz burst processing has increased interest in high-repetition-rate laser sources. Electro-optic (EO) frequency combs are promising due to their excellent controllability and GHz-range tunability. However, the modulation process that generates EO combs produces M-shaped spectra with pronounced side peaks containing high-order chirped components. These can degrade amplification efficiency and limit pulse distribution quality due to incomplete temporal compression. In this study, we implemented a 24-W EO comb-based picosecond laser system and applied programmable spectral shaping with a 0.7-nm Gaussian-filter to suppress spectral side peaks. As a result, temporal energy confinement of compressed pulse was significantly improved from 53.1 to 92.8% while maintaining comparable output power and pulse duration. These findings demonstrate that spectral shaping can effectively enhance the temporal quality of EO comb pulses, supporting their application in high-precision GHz-burst micromachining.

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Enhancing Chatter Vibration Analysis in Turning Processes through Advanced Multiple-denoising Wavelet Techniques: Chanikan Pomusa, Bandit Suksawat; J. Korean Soc. Precis. Eng. 2025;42(4):273-284.
Published online April 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.128

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This study investigated the natural frequency of a self-excited vibrating workpiece and cutting tool using a hammer impact test to acquire vibration data. Time-domain cutting vibration data were converted to the frequency domain using FFT. The workpiece signal exhibited a high amplitude, peaking at 392 Hz, while the cutting tool signal presented a peak at 930 Hz. Stability Lobe Diagrams were constructed to assess dynamic stability. Cutting experiments revealed an obvious relationship between spindle speed and signal amplitude, with higher speeds leading to larger amplitudes. Frequency analysis revealed a peak near the cutting tool's 900 Hz natural frequency. Smoother surface finishes were observed at 0.15 mm cutting depth, while 0.2 mm resulted in a wavy surface, indicating chatter. To investigate chatter frequency and reduce noise, a multiple-denoising method combined Bior 3.7 and DB10 wavelets to reduce amplitude and improve signal representation, especially for non-smooth features. The proposed method aimed to reduce the 900 Hz cutting tool’s natural frequency. Results showed a clear chatter frequency at 450-480 Hz for 0.2 mm depth cuts at spindle speeds of 500, 1,000, and 1,400 rpm. The proposed method exhibited high efficiency, achieving the higher signal-to-noise ratio and lower mean-square error than Bior 3.7 and DB10 wavelet denoising techniques.

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A Review of Intelligent Machining Process in CNC Machine Tool Systems
Joo Sung Yoon, Il-ha Park, Dong Yoon Lee
International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2243. CrossRef

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Remote Detection Technique of Trace Leak Gas based on Frequency Modulation Absorption Spectroscopy: Jungjae Park, Jae Yong Lee, Jae Heun Woo, Jonghan Jin; J. Korean Soc. Precis. Eng. 2024;41(10):741-746.
Published online October 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.087

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The LIDAR principle is used in a variety of fields, including large-scale pipeline facility management, industrial disaster safety control, and atmospheric environmental monitoring, to employ the remote gas detection technique. In this study, we designed and implemented a remote detection method for N2O gas leaks using absorption spectroscopy based on frequency modulation of a Mid-IR quantum cascade laser (QCL) with a wavelength of 4.5 μm. We direct the frequency-modulated beam, locked to a single absorption line of N2O, to a leak hole on a target surface within a range of approximately 50 m. For area scanning around the leak point, we use a galvano scanner to deflect the probe beam. The back-scattered beam from the diffuse target surface is then collected by a Cassegrain telescope with a diameter of 300 mm and detected by an InSb photo-detector with high photon sensitivity. To process the detected signal, we utilize fundamental and second harmonic detection with a lock-in amplifier, resulting in a relative gas concentration expressed as the second harmonic signal normalized by the fundamental signal. Our test results demonstrate that this proposed method can detect gas leaks as small as 0.005 sccm at a distance of 50 m.

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Model-based Motion Control Design of a Linear Motor Stage in Frequency Domain: Hee Won Jeon, Hyeong-Joon Ahn; J. Korean Soc. Precis. Eng. 2024;41(1):55-60.
Published online January 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.107

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The fourth industrial revolution led to advanced servo systems, enhancing productivity across industries. However, designing these systems remains challenging due to the performance-stability trade-off. This paper presents a model-based motion control of a linear motor motion stage in frequency domain. A user-code for the PowerPMAC commercial controller was developed to excite motion control system so that we could get a frequency response. The theoretical frequency response of the servo algorithm was compared with the experimental frequency response. Based on this, a tuning graphical user interface (GUI) was developed to predict performance when the servo loop gain is changed. Especially, to compensate for residual vibrations caused by high acceleration and deceleration and to improve tracking error, DOB (Disturbance Observer) and ILC (Iterative Learning Control) control techniques were applied in the frequency domain. Through the design of the frequency domain motion controller, the control performance of the linear motor motion stage could be predicted with over 96% accuracy, resulting in a 54.32% improvement in tracking error and a 93.56% improvement in settling time, 85.29% in RMS error.

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Fuzzy Neural Network Control for a Reaction Force Compensation Linear Motor Motion Stage
Kyung Ho Yang, Hyeong-Joon Ahn
International Journal of Precision Engineering and Manufacturing-Smart Technology.2024; 2(2): 109. CrossRef
Customized Current Control of a Linear Motor Motion Stage
Kyung Ho Yang, Hyeong-Joon Ahn
Journal of the Korean Society for Precision Engineering.2024; 41(11): 875. CrossRef

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Study on Automated Heat Treatment for Car-body Mold Using an Articulated Robot System: Kee Jin Park, Sung Ho Yoon; J. Korean Soc. Precis. Eng. 2023;40(12):1011-1018.
Published online December 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.111

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The quality and quantity of heat treatment in mold processing can vary depending on the skill level of the equipment operator. Therefore, study on ways to overcome these disadvantages are essential. This study aimed to increase the antiwear properties of molds through high-frequency induction heat treatment and laser heat treatment processes. The heat treatment was applied to the surfaces of molds used in car body production using an articulated robot, to achieve long-term use and quality maintenance. Additionally, an articulated robot system based on redundant degrees of freedom suitable for mold heat treatment processes was designed, and its operational efficiency was verified through virtual environment simulations. Furthermore, heat treatment was validated through on-site testing of the robot system. Its effects were analyzed according to mold materials and shape conditions, ultimately deriving the optimal robot heat treatment conditions. Finally, off-line programming (OLP) in virtual processes was proposed to minimize robot setup time and maximize production efficiency. The conditions for articulated robot automated heat treatment obtained in this study can be preapplied in simulation environments when generating heat treatment robot programs based on OLP. They can be utilized for optimizing the quality of mold heat treatment in car body production.

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Design and Dynamic Characteristics Analysis of Rotating Welding Torch with Ball Joint Type Mechanical Seal structure: Dong Jun Lee, Jung Min Kim, Chul Soo Jeong, Sangrok Jin; J. Korean Soc. Precis. Eng. 2023;40(11):881-889.
Published online November 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.063

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This paper proposes a new rotary welding torch with a ball-jointed mechanical seal structure that simultaneously realizes the enclosure of CO₂ gas, the energization of welding current, and the insulation for system protection. In order to effectively compare the operation mechanism of the proposed device with the conventional rotary welding torch, a schematic technique is introduced to clearly visualize the operation and connection structure of the model. The kinematic state and constraint degrees of freedom of the tool are clearly shown, and it is easy to distinguish between the two designs that use different component parts and connection structures but result in the same final motion. In addition, the four dynamic characteristics of a rotary torch operating at 20 Hz (driving torque, vibration reaction force, natural frequency, and inertial mismatch) were analyzed to demonstrate superior performance to conventional products. The welding test showed that the tool normally operated even in a harsh welding environment, verifying its applicability in the field.

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Analysis of Electromagnetic Field and Temperature Distribution around Narrow Gap in High-frequency Resistance Welding of Steel Pipe: Young Soo Yang, Kang Yul Bae; J. Korean Soc. Precis. Eng. 2023;40(10):829-837.
Published online October 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.053

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When a narrow gap was formed under appropriate welding conditions in the steel pipe manufacturing process using highfrequency resistance welding, temperature distribution was analyzed to predict the length of the gap. Assuming the length of the gap from the apex point to the welding point at an applied voltage, and calculating the temperature distribution around the gap, the length of the gap with an appropriate fusion width at the welding point could be estimated. Along with this, the current density and magnetic flux density distributions that appeared in the narrow gap were obtained according to the change in the applied voltage, and the distribution shape and size of the electromagnetic force acting on the gap were also predicted. The current density, magnetic flux density, and electromagnetic force gradually increased along the narrow gap, showing the maximum value at the welding point. In the temperature distribution in the narrow gap, the surface of the front end began to melt at an appropriate applied voltage, and the melting width was the largest at the welding point. As the applied voltage increased, the narrow gap became longer, and the appropriate gap length appeared in proportion to the applied voltage.

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Analysis of Stress Distribution around the Weld Zone in High Frequency Resistance Welding of Steel Pipe
Young-Soo Yang, Kang-Yul Bae
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(6): 21. CrossRef

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Optimization Design of Student KSAE BAJA Knuckle Using SLM 3D Printer: Young Woo Im, Geon Taek Kim, Hyeon Sang Shin, Kang Min Kim, Bu Hyun Shin, Jong Won Lee, Jinsung Rho; J. Korean Soc. Precis. Eng. 2023;40(9):719-724.
Published online September 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.028

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With advancements in the 3D printing technology, many industrial sectors are transitioning from traditional production methods, such as cutting processing, and casting, to utilizing 3D printers for manufacturing. For instance, in the automotive industry, the production of vehicle upright knuckle parts typically involves casting followed by machining processes, such as turning and milling, to achieve dimensional accuracy. However, this approach is associated with high processing costs and longer lead times. This study focuses on the production of vehicle upright knuckle parts using a selective laser melting (SLM)-type 3D printer, with SUS 630 as the material. To evaluate the feasibility of utilizing this method in industrial vehicles, this study conducts static and modal analyses, along with topology optimization. Additionally, experimental test drives are performed with the parts installed in KSAE BAJA vehicles, and modal frequency experiments are conducted. The objective of these analyses and experiments is to assess the performance, reliability, and applicability of utilizing SLM-based 3D printing for manufacturing vehicle upright knuckle parts by optimizing the design through topology optimization and evaluating the results through experiments and analysis.

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High-frequency Heat Treatment Simulation of Park Gear considering Coil Current Calculation and AISI 1552 Phase Transformation: Jin Kyu Choi, Seok Soon Lee; J. Korean Soc. Precis. Eng. 2023;40(5):399-407.
Published online May 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.136

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This study performed high-frequency heat treatment experiments and simulations of the park gear of an automobile transmission. The heating temperature and hardening depth were measured during high-frequency heat treatment. Moreover, by applying the resonance RCL circuit, the current value of the coil during high-frequency heat treatment, the electromagnetic and heat transfer material properties dependent on the temperature, and the phase transformation function were all applied to the simulation. In the high-frequency heat treatment experiment, the heating temperature was 977.4℃ and the 1st direction hardening depth was 1.5 mm, the 2nd direction hardening depth was 3 mm, and the 3rd direction hardening depth was 2.5 mm, and the reliability was verified by comparing the simulation heating temperature of 1,097℃ and the 1st direction predicted hardening depth of 1.6 mm, the 2nd direction predicted hardening depth of 2.8 mm, and the 3rd direction predicted hardening depth of 2.7 mm. The error rate of the heating temperature results was 12.2% whereas that of the hardening depth results was 7.1%.

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Frequency Domain Identification and Model-based Disturbance Observer for a Mini Drone: Kyu-Hwan Chung, Hyeong-Joon Ahn; J. Korean Soc. Precis. Eng. 2023;40(5):383-388.
Published online May 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.134

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Drone is an innovative industry that can combine the application of various technologies in the fourth industrial era, such as big data, artificial intelligence, and ICT. Although the synergy effects of these technologies will be great in various industrial ecosystems, drones are vulnerable to gusts such as "building wind" or "valley wind". Herein, the frequency domain of a mini drone was identified and a model-based disturbance observer (DOBs) was applied to implement the drone robust resistance against gusts. The frequency response of the Parrot Mambo or mini drone was measured with multi-sine excitation and the system dynamic parameters were identified. Based on the identified model, DOBs were designed and applied to the drone’s altitude, position, and yaw control. The effectiveness of the DOBs was verified with a sinusoidal disturbance. With the model-based DOB, 84.5% of the drone altitude responses, 50.7% of x responses, 52.1% of y responses, and 79.7% of yaw responses against sinusoidal disturbances were reduced. Flight responses were measured against wind disturbances with changing speed and direction. With the model-based DOBs, the drone"s altitude decreased by 87.7%, the x position by 53.0%, the y position by 60.6%, and the yaw angle by 56.2%.

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Optimal Design of Microwave Shielding Door by Using of Design of Experiments: Ka Hee Lee, Kwang Kim; J. Korean Soc. Precis. Eng. 2023;40(1):13-19.
Published online January 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.104

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In the heating and drying system using microwaves, an optimal design method was presented to effectively shield microwaves leakage between the door and the cylindrical applicator. In order to protect the human body from leaking microwaves, it is necessary to keep the intensity of microwaves below 5 mW/cm². The door part adopts a choke structure and includes a number of design factors, such as, fin shape, slit shape, and a gap between the applicator and the door. The geometry was optimized by design of experiments, applying full factorial design and response surface method in a 4-factor, 2-level design. The results obtained by ANSYS HFSS analysis were applied to the intensity of microwave leakage according to the change of the design factors. The shape of the choke structure was optimized using Minitab, a statistical program. The microwave heating and drying system was manufactured based on optimal design value and the leakage of microwaves between the door and the applicator was measured. We confirmed that the experimental values were consistent with the simulation values.

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Numerical Analysis of High Frequency Electric Resistance Welding Process of Steel Pipe: Young Soo Yang, Kang Yul Bae; J. Korean Soc. Precis. Eng. 2022;39(12):931-938.
Published online December 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.093

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The high-frequency electric resistance welding (HF-ERW) process is widely used in the steel pipes production because it can weld at a high speed, has excellent weldability, and attains clean and precise shapes. However, for process improvement, analytic studies on electromagnetic field and temperature distributions, and selection of appropriate process variables are required. In this study, finite element analysis models that can analyze the electromagnetic field distribution and temperature distribution in the HF-ERW of a steel pipe were proposed, in consideration of the characteristics of the process, including electromagnetic phenomena localized to the workpiece surface and fast welding speed. By applying the proposed analysis models, changes in current density, magnetic flux density, generated heat density, and fused width in the pipe could be predicted according to changes in process variables such as the V angle of the strip, the electrode position, and the source voltage. Through comparison with the analysis and the limited-case experiment, the analysis result predicted the actual fused width fairly well, and the validity of the proposed model could be verified.

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Characterization of an electric resistance welded steel plate
K. K. Patel, R. Nagar, D. Chauhan
Practical Metallography.2025; 62(5): 331. CrossRef
Analysis of Stress Distribution around the Weld Zone in High Frequency Resistance Welding of Steel Pipe
Young-Soo Yang, Kang-Yul Bae
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(6): 21. CrossRef
Analysis of Electromagnetic Field and Temperature Distribution around Narrow Gap in High-frequency Resistance Welding of Steel Pipe
Young Soo Yang, Kang Yul Bae
Journal of the Korean Society for Precision Engineering.2023; 40(10): 829. CrossRef

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Assessment of Muscle Fatigue Using EMG under Long Duration and High Intensity Fatigue Condition: Dahyun Nam, Kiwon Park; J. Korean Soc. Precis. Eng. 2022;39(6):433-441.
Published online June 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.020

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Evaluation of local muscle fatigue has been conducted over past decades to investigate the process of fatigue accumulation and to reduce effect of fatigue in EMG field. The purpose of this study was to investigate fatigue in isotonic contractions, which can inflict the same fatigue on the subject during dynamic contractions. Local muscle fatigue was measured by changing the load level and exercise time in dumbbell curl comprising isotonic contractions through power spectrum changes. Five healthy males and five healthy females performed dumbbell curls with 1 kg load for two minutes, and on other days when no fatigue occurred due to the previous exercise, performed for one minute with a 2 kg load. The muscle fatigue was estimated by median frequency before and after fatigue, the decrease was greater than in the trial wherein a load of 2 ㎏ was applied for one minute than in the trial where a load of 1 kg was applied for two minutes for the females. The decrease in the median frequency is quantitative data indicated by the slowing of the motor unit actional potential (MUAP), suggesting exercise intensity is more sensitive to the slowing of the MUAP than the exercise duration.