Journal of the Korean Society for Precision Engineering

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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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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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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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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A Study on the Excitation Force Identification of a Multi-Input System Using Inverse Stiffness Method: Jun-heon Lee, Kwanju Kim; J. Korean Soc. Precis. Eng. 2022;39(2):115-122.
Published online February 1, 2022; DOI: https://doi.org/10.7736/JKSPE.021.106

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The purpose of this study was to investigate the excitation force that generates the vibration of the reduction gear case for railroad vehicles. This excitation force is difficult to measure directly. The inverse stiffness method was used using the acceleration response measured in the experiment and the vibration response function derived from the finite element analysis. It was assumed that the excitation force acting on the reduction gear operates in the X, Y, and Z directions for each bearing, and a total of 12 excitation forces were investigated. When deriving the excitation force, singular value decomposition was applied to the vibration response function to increase the accuracy of the result. The results of the excitation force according to the number of degrees of freedom of the response were compared. Additionally, the magnitude of the estimated excitation force according to the singular value category used was compared, and it was confirmed that a too low singular value indicates a different excitation force.

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Recent Trends on a Precision Dimensional Sensor Using Optical Modulation Techniques: Yoon-Soo Jang, Jungjae Park, Jonghan Jin; J. Korean Soc. Precis. Eng. 2021;38(12):889-896.
Published online December 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.083

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Optical dimensional metrology has playing a long-term key role from high-precision engineering to large-scale industrial manufacturing. Various methods of optical dimensional metrology have been proposed and demonstrated to respond to the ever-growing industrial demands as well as fundamental science demands for the measurement precision and range. However, most of them demonstrated under laboratory conditions have a long way to go outside the laboratory. Here, we present a progress review on optical modulation technique-based dimensional metrology, which has already been used in real applications and has been commercialized. Amplitude modulation (AM) and frequency modulation (FM) based dimensional measurement techniques are described with their operating principles, and recent progresses and applications in 3D imaging are presented in this review.

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Frequency Analysis of the Servo System with Three-Stage Reducer considering the Backlash Ratios and Motor Input Voltage: Joo Hyun Baek, Tae Young Chun, Jong Geun Jeon, Young Hwan Jo; J. Korean Soc. Precis. Eng. 2021;38(9):691-699.
Published online September 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.064

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This paper proposed the simulation model of the servo system with three-stage reducer and presented the result of frequency analysis of the servo system considering backlash ratios and motor input voltage. By virtue of this work, we realized that if the motor input voltage of the system was large, the influence of each stage backlash ratio could be minimized or removed. Besides, we also found that if the motor input voltage was small, this created an optimal backlash ratio combination which could maximize the anti-resonance and resonance frequency of the servo system. This paper could be useful for determining each stage backlash ratio in designing a three-stage geared servo system with fast response.

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Vibration Analysis for Developing Ultrasonic Kitchen Knife for Cutting Foods: Do Hwan Kang, Ji Won Seo, Dong Sam Park; J. Korean Soc. Precis. Eng. 2021;38(6):447-454.
Published online June 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.018

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Ultrasonic cutting is used not only for cutting various materials such as metals and non-metals, but also for bone cutting of the human body or for various surgical operations. In recent, ultrasonic cutting technology is being applied for cutting various food products such as cakes, pizza, and cheese. It is shown that ultrasonic vibrations for cutting food products enables high-precision and high-quality cutting, and the quality of the cutting surface is affected by the shape of food products and cutting conditions. However, most of the studies have been on industrial cutting horns that can be used in large-scale grocery factories, but these cutting horns are very different from the shape of knives used in the households. Accordingly, research or technology development for ultrasonic cutting knives that can be used in household has not been studied. Therefore, this study developed a knife that can cut or process food by applying ultrasonic vibration while having a shape similar to the existing knife as possible so that it can be used in general. To develop such a knife, a modal analysis was performed using the finite element method for knife models of various shapes, and a suitable model for a kitchen knife was proposed.

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Development and Performance Verification of an Ultrasonic Food Cutter
Byung-Soo Yang, Ji-Chan Suk, Jeong-Suk Seo, Dong-Sam Park
Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(5): 54. CrossRef

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Developed an In-Line System of Measuring MTF for Automating the Assembly Process of Lens-Module in a Smartphone Camera: Sangseon Lee, Hojae Lee; J. Korean Soc. Precis. Eng. 2021;38(5):359-363.
Published online May 1, 2021; DOI: https://doi.org/10.7736/JKSPE.020.111

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In this paper, we would like to introduce an in-line MTF (Modulation Transfer Function) measuring system which is compatible with the automated assembly process line of lens-modules in smartphone cameras. This in-line optical inspection system consists of a resolution chart module, Dual Cono-Scope Telecentric Lenses, imaging lenses, and a single detector. Unlike conventional measuring devices with many cameras that are more commonly used in the industry, this device can evaluate the MTF performance without reversing the lens module in an upside down position by applying a reverse projection method. So, it is possible to measure MTF for the full-fields of the lens module from any arbitrary desired positions, as well as the designated positions by using a single camera. This makes it compatible with the equipment of the automated production process line for lens modules. We will expect that the lens module production line will be diversified and fully automated through the application of this in-line optical inspection system.

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Fabrication and Characterization of Automotive Aspheric Camera Lens Mold based on Ultra-precision Diamond Turning Process
Ji-Young Jeong, Hwan-Jin Choi, Jong Sung Park, Jong-Keun Sim, Young-Jae Kim, Eun-Ji Gwak, Doo-Sun Choi, Tae-Jin Je, Jun Sae Han
Journal of the Korean Society for Precision Engineering.2024; 41(2): 101. CrossRef
SEM Image Quality Improvement and MTF Measurement Technique for Image Quality Evaluation Using Convolutional Neural Network
Chan Ki Kim, Eung Chang Lee, Joong Bae Kim, Jinsung Rho
Journal of the Korean Society for Precision Engineering.2023; 40(4): 275. CrossRef

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Effects of Bearing Locations on the Characteristics of a Spindle System Supported by Tapered Roller Bearings: Van-Canh Tong, Jooho Hwang, Seong-Wook Hong; J. Korean Soc. Precis. Eng. 2020;37(8):615-624.
Published online August 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.018

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This paper presents the effects of bearing locations on the mechanical characteristics of a multi-stepped spindle system related to bearing fatigue life, natural frequency, and static stiffness. The multi-stepped spindle is supported by a pair of tapered roller bearings (TRBs) and subjected to radial loading. To solve the equilibrium equation of the spindle system which is inherently statically-indeterminate, this study adopts an integrated shaft-bearing model, where the spindle is modelled by the finite shaft elements and the supporting TRBs are modelled by the five degrees-of-freedom TRB model developed by the authors. An iterative computational method is used to estimate the spindle deflection coupled with bearing deflections, and afterwards the bearing stiffness and internal contact loads of rolling elements are computed. The bearing fatigue life based on the ISO standard and the first natural frequency of the spindle system are evaluated with the spindle-bearing model. The influences of bearing locations on the static stiffness and natural frequency of the spindle, and the fatigue life of TRBs are rigorously investigated. The numerical results show the noticeable effects of bearing locations on the spindle system characteristics. The presented results provide a comprehensive assessment to aid for design optimization of spindle-TRB system.

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Compliance Analysis and Design Optimization of a 2-DOF Precision Positioning Stage based on Serial Mechanism for Enhanced Resonance Frequency Isotropy: Hyun-Pyo Shin; J. Korean Soc. Precis. Eng. 2020;37(6):465-472.
Published online June 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.008

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Precision positioning stages are devices for precisely positioning objects according to required degrees of freedom and performance. Precision positioning stages are classified into serial and parallel mechanisms. Except for specific applications, the parallel mechanism is preferred. In serial mechanism, dynamic characteristics such as resonant frequency are clearly different from axis to axis and the first resonance frequency is distinctly low compared to the second. These make the control performance different for each axis and incurs limitation in control. In this study, the first and second resonant frequencies in a serial 2-DOF precision positioning stage were increased while maintaining their approximal value. Compliance analysis for the stage was performed by applying the matrix based method. A new concept of resonant frequency isotropy (RFI) was introduced and design optimization was performed in which first and second resonant frequencies almost coincided. This optimization allowed for the design of a serial 2-DOF precision positioning stage with enhanced first resonance frequency by 50.8% and RFI by 80.2% compared to the initial design. This paper is expected to increase the use of precision positioning stages based on serial mechanism and apply the concept of RFI to the positioning stages with more than 2-DOF.

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Comparison of PSD Analysis Methods in Frequency Domain Fatigue Analysis: Joon Jang, Jae Myung Cho, Kwang Hee Lee, Won Woong Lee, Woo Chun Choi; J. Korean Soc. Precis. Eng. 2019;36(8):737-743.
Published online August 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.8.737

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If fatigue failure occurs during aircraft operation, it can cause catastrophic injuries. So, it is necessary to study fatigue failure at the design stage. Frequency domain fatigue analysis is used to predict fatigue failure. During frequency domain fatigue analysis, results can be calibrated by PSD analysis. In this study, fatigue failure is predicted by the Dirlik method, Lalanne method and Steinberg method. Regarding results, life determined by the Dirlik method, Lalanne method and Steinberg method were 8.737, 8.314, and 7.901 times the standard life, respectively. The Steinberg method is the most conservative but the difference with other methods was approximately 10%. In the cycle histogram, the Dirlik method had more counts than the Lalanne method in lower stress range. However, it does not affect the life of material used in this study. However, if material has a lower fatigue limit or stronger PSD data is used, life difference will occur.

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Analysis of Acoustic Load Fatigue Life of Skin of POD for Aircraft considering Aspect Ratio
Wonwoong Lee, Jaemyung Cho, Jongin Bae, Hoonhyuk Park
Journal of the Korea Institute of Military Science and Technology.2025; 28(2): 126. CrossRef
A Study of Vibration Analysis of 100 MPa Class Fitting Thread for Mobile Hydrogen Charging Station
JUNYEONG KWON, SEUNGJUN OH, JUNGHWAN YOON, JEONGJU CHOI
Transactions of the Korean Hydrogen and New Energy Society.2024; 35(1): 83. CrossRef
Very high cycle fatigue on gas metal arc butt-welded AA6061-T6 plates
Iksu Kim, Moon G. Lee, Martin Byung-Guk Jun, Jungho Cho, Yongho Jeon
Journal of Mechanical Science and Technology.2023; 37(12): 6649. CrossRef
Vibration-Based Fatigue Analysis of Octet-Truss Lattice Infill Blades for Utilization in Turbine Rotors
Sajjad Hussain, Wan Aizon W. Ghopa, S. S. K. Singh, Abdul Hadi Azman, Shahrum Abdullah, Zambri Harun, Hawa Hishamuddin
Materials.2022; 15(14): 4888. CrossRef
Experimental Verification of Dirlik Fatigue Evaluation in Frequency Domain Using Beam Structure under Random Vibration
Eunho Lee, Siyoung Kwak
Transaction of the Korean Society of Automotive Engineers.2021; 29(2): 157. CrossRef

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High-Stable RF-Frequency Generation Using a Microcontroller for Amplitude Modulation Based Absolute Distance Measurement: Yeongjin Yu, Joohyung Lee; J. Korean Soc. Precis. Eng. 2019;36(7):605-609.
Published online July 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.7.605

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In this paper, we describe high-stable RF-frequency generation using a low-cost 8-bit microcontroller for amplitudemodulation based distance measurement, which is one of the indispensable technologies for cost-effective Lidar application. The RF frequency generator using the microcontroller was implemented by externally referencing to an atomic clock and 8- bit timer/pulse width modulation (PWM) functions, which are embedded in a microcontroller. The microcontroller we used was ATmega128 of Microchip with 16 MHz clock and 8-bit timer, which generates the maximum frequency of up to 62.5 kHz, enabling 2.4-kilometer ranging without phase ambiguity. The stability of RF-frequency generated from the implemented system was evaluated in terms of Allan deviation using a commercial frequency counter. The stability indicated 10^-11 at 1-s averaging time and 10^-12 at 100 s averaging time, which represents a 1/10 degradation compared to the stability of the commercial function generator. Along with the stability evaluation, we interrogated frequency tunability, which extends a measurable range without phase ambiguity.