In this research, a precise on-machine line-profile measuring system that compensates for the motion-error from the linear-guide, which can influence the accuracy of the measurement of the profile was developed. For this purpose, the principle of measuring the system model was used to analyze the compensating motion error component for line-profile and 3 types of MPES method (Integration-Method, the Fourier-Model-Method, and the Sequential-Method). The multi-probe-error-separation-method (MPES) was applied to calculate the motion-error, which in turn was used to compensate for the measured linear-profile of the specimen. Lastly, the simulation conditions involving a multi-probe measurement system consisting of a reference-artifact, capacitive-sensor, and three displacement-sensors were designed and Monte-Carlo simulation was implemented for the evaluation of the 3 types of MPES method. Also, the simulation results obtained from the conventional measuring system and the proposed system were compared for the verification of the performance of the latter. Consequently, efficient compensation of the motion error appeared as possible and the applicability of the multi-probe measurement system was confirmed.
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
To monitor the stirring state by on-line estimation of liquid viscosity instead of stopping the stirring process and measuring the viscosity using viscometer, a basic study clarifying the effect of stirring conditions was carried out. For this purpose, the relationship between liquid viscosity and the stirring conditions, such as stirring torque, stirring speed, the duty ratio of PWM, impeller and beaker type, and the blade position in the beaker was analyzed. The second-order relationship between the stirring speed and torque, the linear relationship between viscosity and torque, and the linear relationship between duty ratio of PWM and stirring speed were observed, thereby indicating that the liquid viscosity could be estimated by an experimental formula based on the duty ratio and the stirring speed. In addition, the type of impeller and beaker was identified using the magnetic field inside impeller and RFID technology. For reducing the error in calculating the liquid viscosity, the employment of an impeller blade with a large rotational resistance and stirring with the blade at the center zone of the beaker were found to be necessary.
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A Study on Contactless Identification of Impellers Using a Digital Hall Sensor Ho-Cheol Lee Journal of the Korean Society of Manufacturing Process Engineers.2021; 20(12): 71. CrossRef
In this paper, an integrated ankle torque sensor and mechanism (Foot Link) of a Tendon driven-type wearing walking aid robot were designed. The foot link consists of an ankle torque sensor and a mechanism connected to the footrest. The size of the sensing part of the ankle torque sensor was designed through structural analysis and assembled by attaching a strain gauge. As a result, the reproducibility error and the nonlinearity error were within 0.04%, respectively. And the calibration result of the ankle torque sensor, reproducibility error, and non-linearity error were identified to be within 1%, respectively. Therefore, it is proposed that the ankle torque sensor presented in this paper can be used to measure the torque acting on the tendon-driven walking aid robot.
Incremental sheet metal forming can be used to manufacture various products without the punch and die set. However, it is difficult to manufacture the desired shape due to section deflection and springback of the sheet. Section deflection is caused by the force of the blank holder for fixing the sheet and the tool for forming the sheet. In this study, we analyzed the characteristics of the section deflection according to the geometries of the circular cup shapes in the sheet incremental forming process. The section deflection increased with an increase in the entering radius and forming angle in the section deflection region. However, section deflection was constant according to the exit radius. In addition, the secondary forming process for reducing the shape error was introduced. The secondary incremental forming process was conducted in the opposite direction. Characteristics of the shape error according to the entering depth of the tool among the forming parameters for reducing the shape error of the cup shape were analyzed. The springback in the cup-shape was reduced by the additional forming process with an optimum entering depth of the tool.
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Study on the Incremental sheet metal forming process using a metal foam as a die Jae-Hyeong Yu, Kyu-Seok Jung, Mohanraj Murugesan, Wan-Jin Chung, Chang-Whan Lee International Journal of Material Forming.2022;[Epub] CrossRef
Study on the Incremental Sheet Forming Process with the Ball Type Tool Jun-Hyun Kyeong, Byeong-Hyeop Lee, Sun-Jae Lee, Kyeong-Hoon Cho, Hyung-Won Youn, Chang-Whan Lee Journal of the Korean Society for Precision Engineering.2022; 39(5): 371. CrossRef
Tool Path Design of the Counter Single Point Incremental Forming Process to Decrease Shape Error Kyu-Seok Jung, Jae-Hyeong Yu, Wan-Jin Chung, Chang-Whan Lee Materials.2020; 13(21): 4719. CrossRef
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.
By patterning finely with a laser with a thickness of 100 μm or less such as ABS and forming an electronic circuit through plating, a high-density flexible PCB applicable to wearable and mobile devices can be realized. ABS films with a thickness of 60, 90, and 120 μm were prepared, and a crater measuring 100 μm or less was formed by irradiating a fiber laser with a wavelength of 1064 nm with a single pulse. The size of the craters is affected by the intensity of laser irradiation and the thickness of the film, and the heat dissipation layer reduces the change in size caused by the difference in the thickness of the film. For films with a thickness of 60 μm, it has been found that small craters of more than 10% can be obtained due to the heat dissipation layer. Thermal analysis showed in the ABS film without the heat dissipation layer, the maximum temperature increased to 373oC, but decreased to 261℃ in the ABS film with the heat dissipation layer. With a decrease in the thickness of the film, the heat dissipation layer further reduces the pattern by laser irradiation.
In the framework of the 4th industrial revolution, modern machine-building rapidly converges with IOT technology. This requires very high precision machining of the parts and assemblies, such as electronics, vehicle and components, agricultural and construction machines, optical instruments, and machine tools. However, high precision machinery is quite expensive, and there exists a general need for low-cost equipment. While many researchers are working on this, their major focus is on cutting tools. This study aimed to compensate for errors and enhance machinery precision by adding a servo controller to the processing unit. Consequently, the study is on servo control and processing precision for processing utilizing ECTS (Error Compensation Tool Servo) to compensate for errors.
In this study, blades manufactured by 3D printing technology were experimentally tested to be used for a scaled wind turbine in a wind tunnel. The scaled model was originally designed and manufactured by researchers at the Technical University of Munich. The model has been slightly modified to adopt the 3D printed blades for this study. Also, control algorithms for the power maximization in the low wind speed regions were constructed and applied to a commercial programmable logic controller for wind tunnel tests of the scaled model. For comparison, the scaled model was also modeled in MATLAB/Simulink and dynamic simulations were performed with the measured wind speed as an input. The simulation results seemed to overpredict the experimental results initially, but by considering the unexpected extra generator torque due to friction of the shaft, the errors were reduced to be less than 5%. Based on this study, the application of 3D printed blades to the wind turbine scaled models of a similar rotor diameter was found to be an efficient and effective way of blade manufacturing and scaled model testing.
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Performance Validation of Control Algorithm Considering Independent Generator Torque Control in PCS Dongmyoung Kim, Min-Woo Ham, Insu Paek, Wirachai Roynarin, Amphol Aphathanakorn Applied Sciences.2024; 14(24): 11598. CrossRef
The Suitability of Substructures of the Offshore Wind Power Complex Dae Kyung Kim, Dong Soon Kang, Jong Hak Lim, Young Il Byun, Chul Ki Song Journal of the Korean Society for Precision Engineering.2022; 39(4): 299. CrossRef
CFD Analysis of the Mechanical Power and the Wake of a Scaled Wind Turbine and Its Experimental Validation Yechan Hwang, Insu Paek Journal of the Korean Society for Precision Engineering.2021; 38(3): 223. CrossRef
Design and Validation of Demanded Power Point Tracking Control Algorithm for MIMO Controllers in Wind Turbines Taesu Jeon, Dongmyoung Kim, Yuan Song, Insu Paek Energies.2021; 14(18): 5818. CrossRef
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