The purpose of this paper was to develop a simulation model for a 40 kW electric tractor using a powertrain based on dual motors and a planetary gear. To select motor capacity and reduction gear ratio based on the power flow for agricultural work, load data for various gear conditions were acquired and analyzed using a 42 kW engine tractor of similar capacity. Modeling was conducted using MATLAB/Simulink/Simscape. Load data acquired through actual field tests were applied as load conditions for the simulation. Simulation results confirmed that the power was transmitted through the planetary gear as the clutch and brake operated according to the work mode. The developed simulation model is expected to be used for electric tractor development.
A feasibility study of electrically assisted solid-state spot joining (EASSJ) of dissimilar aluminum alloys for automobile structures was conducted. EASSJ of dissimilar automotive aluminum alloys (AA6451 and AA6014) was conducted by simultaneously applying step-by-step current and compressive load to the faying interface (lap spot joining), while the temperature was controlled to be lower than melting points of joining alloys. To evaluate the soundness of the joint, a nugget pull-out fracture mode under shear tensile test was set as a criterion. Microstructure analysis was also conducted to evaluate characteristics of the joint. Experimental results suggest that the EASSJ is clearly feasible in joining dissimilar aluminum alloys for automobile structures.
Zinc sulfide (ZnS) is a widely used material in far-infrared and near-infrared imaging systems due to its exceptional optical transmittance properties. Through a hot isostatic compression process, during manufacturing, ZnS undergoes crystal structure modifications, resulting in increased transmittance across the visible and infrared spectra. However, ZnS exhibits low fracture toughness and irregular crystal orientations, making it prone to brittle fracture during the conventional cutting processes. Such brittleness often leads to surface defects that scatter light, diminishing optical transmittance. Therefore, understanding the conditions conducive to ductile processing is critical and necessitates a thorough brittle fracture analysis. This study introduces a novel quantitative analysis method to determine the occurrence of ductile processing and brittle fracture in ZnS materials after the turning process. To validate the efficacy of this approach, experimental machining was conducted through diamond turning and magnetorheological fluid polishing processes. Subsequently, a comprehensive quantitative assessment of brittle fracture was performed. Additionally, the relationship between brittle fracture and optical transmittance was explored using the proposed analysis method.
In this study, the structural integrity of an engine-generator support structure of hybrid drone is verified through finite element (FE) analysis and experimental investigation. From preliminary experiments, critical failures in four columns of the support structure were observed. Due to the repeated cyclic loads induced by the engine-generator operation, the results of the FE simulation pointed out that fatigue failure is the main cause. To improve the structural integrity, the geometric shape and the material of the structural members are modified and changed, and the safety factor is also reviewed using static structural analysis. The possibility of critical resonance is evaluated through FEM-associated modal analysis and a series of vibration tests. As result, it is confirmed that the re-designed support structure was structurally improved with enough safety margin through FE analysis and experimental investigation, and fatigue life by comparing the predicted value and S-N curve of the material used to the support structure was improved.
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A Study on Structural Integrity Improvement of Cargo Drone through FE Simulation and Topology Optimization Jong Seop Seong, Ha-Young Shi, Beom-Soo Kang, Tae-Wan Ku Journal of the Korean Society for Precision Engineering.2023; 40(9): 685. CrossRef
Actuators for exoskeleton robots comprise various types such as electric, hydraulic, and pneumatic and it is necessary to apply the correct actuator according to the purpose. Most exoskeleton robots mainly use electric actuators, and some special-purpose robots, such as for heavy-load transport requiring large force, use hydraulic actuators. In this paper, friction of the actuation module consisting of a harmonic drive and a brushless DC motor is measured through experiments. And the friction characteristics of the actuation module are analyzed. The harmonic drive transmission system has various advantages, but it also has hysteresis and nonlinear friction characteristics. The friction compensation control of the actuation module enables precise control of the exoskeleton robot, and improves the robot’s performance. Appropriate friction model selection and design affects friction compensation performance. In this study, static and dynamic friction models are designed and analyzed based on the friction data of the actuation module.
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Method for Radial Stiffness Measurement of Strain Wave Gear Flexspline Sangwoong Lee, Daegwon Koh, Jong-Geol Kim, Murim Kim Journal of the Korean Society for Precision Engineering.2024; 41(12): 923. CrossRef
A Recurrent Neural Network for 3D Joint Angle Estimation based on Six-axis IMUs but without a Magnetometer Chang June Lee, Woo Jae Kim, Jung Keun Lee Journal of the Korean Society for Precision Engineering.2023; 40(4): 301. CrossRef
Friction Compensation of Electric-Motor Driven Revolute Joint with Harmonic Gear Seong-Hee Cho, Young-Seog Kim, Jung-Yup Kim Journal of the Korean Society of Manufacturing Technology Engineers.2020; 29(3): 259. CrossRef
Printed electronics is a technology which is used for manufacturing flexible electronic devices dubbed as next-generation electronics such as wearable applications. To commercialize them, it is important to guarantee their electrical performance under various environmental conditions such as temperature and humidity. Moreover, flexible electronic devices usually undergo mechanical deformations such as bending and twisting, hence, it is necessary to observe the electrical performance of flexible devices under mechanical deformation considering both temperature and humidity. The effects of temperature and humidity on flexible printed electrodes, as an example of the simplest flexible electronics, under static deformation of bending and twisting are studied. Electrodes that do not deform are also strongly affected by temperature and humidity, and the increase in resistances of the electrodes with deformation is highest when twisting. The magnitude of static deformation does not affect the conductivity. The effect of line width is important for the twisting deformation. To commercialize printed electronics devices, the effects of temperature and humidity should be considered, with further consideration of the effects of mechanical deformation on the design of the devices.
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Enhancements of Humidity and Gap-Sensing Properties of Coil-Shaped SnO2 Based on Layered Sputtering Method Yang Yang, Luheng Wang IEEE Transactions on Instrumentation and Measurement.2024; 73: 1. CrossRef
This study shows the 4 - Bar linkage design process and static/dynamic stability analysis of a foldable electric wheelchair that can be loaded into a vehicle for long-distance trips. Conventional foldable electric wheelchairs have been developed for indoor use because the safety of the disabled is not secure enough for outdoor use. However, the disabled have generally used foldable electric wheelchairs for outdoor use, potentially putting themselves in a dangerous situation. The body of a foldable electric wheelchair consists of a double 4 - Bar linkage system that shares one link. The architecture of the wheelchair’s four-bar linkage frame was synthesized using four finitely separated design positions. This simple method can design a planar four-bar mechanism through the use of four finitely separated poses (orientation and position). The power driving module includes a battery and controller, and can be separated to load into a car easily. An analysis of the tip-over measurement was performed using ADAMS and LifeMOD during a maneuver on the ground. by force-moment stability metric. Several elements, including the center of gravity position, rotational radius, and acceleration, were evaluated how to affect stability metric.
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A study on the formative usability testing for modular powered wheelchair Jin Hong Kim, Yu Ri Kim, Mi Hyang Han, Soul Han, Eun hye Jeon, Eun Young Hwang, Jae Won Yang, Seon Yeong Lee, Gangpyo Lee Disability and Rehabilitation: Assistive Technology.2025; 20(2): 452. CrossRef
Finite element analyses were carried out to investigate the effect of ultrasonic vibration on drawing force in large diameter tube drawing. Ultrasonic vibration was imposed to a drawing die using ultrasonic vibration horns. The horn was designed to have desired amplification ratio and natural frequency using a wave equation. The drawing forces obtained with and without ultrasonic vibration were compared. The effect of vibration amplitude and phase delay of two horns located in opposite side on drawing force was investigated. Results showed that the drawing force could be reduced about 11% by using ultrasonic vibration of 20 μm amplitude and that the phase shift of two opposite horns had a great effect on the drawing force.
Printed electronics devices are made of several sets of printed patterns. The quality or printability of the printed patterns determines the electrical performance of such devices. Moreover, control of the printability determines the reliability of such devices. Despite its importance, few studies have been reported for the measurement of the printed patterns to evaluate their printability. In this study, a measurement method is proposed for printed patterns, including the definition of the properties to be measured, and the related software is described. The proposed method measures the width, pinholes, and edge waviness and evaluates the printability of the patterns quantitatively. The proposed measurement method could be an efficient tool to evaluate and enhance the printability of printed patterns in printed electronics.
Register control of roll-to-roll printing system for printed electronics requires accurate measurement of register errors. The register marks used for the recognition of patterns position between layers have inherently defects due to low printability of register marks themselves, which brings out inaccurate register accuracy and consequently low performance of printed electronics devices. In this study, the compensation methods for the unrecognized or missing register data are proposed to improve the recognition and consequently the control performance of register accuracy in roll-to-roll printing equipment. The compensation methods using the prior data and the linear interpolation are proposed and compared with the case without compensation for the simulation as well as experiment. Only the linear interpolation method could successfully compensate the missing data and consequently improve the register control performance. We should apply the compensation process of the register errors to improve the register control accuracy in the roll-to-roll printing equipment.
This paper introduces a robot platform which can do weeding while traveling between rice seedlings stably against irregular land surface of a paddy field. Also, an autonomous navigation technique that can track on stable state without any damage of the seedlings in the working area is proposed. Detection of the rice seedlings and avoidance knocking down by the robot platform is achieved by the sensor fusion of a laser range finder (LRF) and an inertial measurement unit (IMU). These sensors are also used to control navigating direction of the robot to keep going along the column of rice seedling consistently. Deviation of the robot direction from the rice column that is sensed by the LRF is fed back to a proportional and derivative controller to obtain stable adjustment of navigating direction and get proper returning speed of the robot to the rice column.
The recent power add-on drive wheelchairs (PADWs) provide greater physical activity and easier transportability and may be an excellent alternative for the typical manual and powered wheelchairs. The driving system consists of a motor and a motor driver is the most important component of the PADW. In this paper, design, implementation, and testing of a driving system for a PADW are presented. To design the output power and torque for the driving system, the equation of motion has been investigated. The motor and driver were fabricated with precise machining and assembled to implement our prototype driving system. The dynamometer test has been carried out using the prototype in order to examine the torque of the system. The experimental results demonstrates that the designed driving system can provide enough output power and efficiency for utilization in a PADW.
In this paper, effects of major design parameters of cold forging dies on die mechanics are quantitatively investigated with emphasis on shrink fit using a thermoelastic finite element method. A ball-stud cold forging process found in a cold forging company is selected as a test process and the effects of die insert material, magnitude of shrink fit, dimension of shrink ring, number of shrink rings, partition of die insert and clamping force on effective stress and circumferential stress are analyzed. It has shown that the number of shrink rings, magnitude of shrink fit, and Young’s modulus of die insert material have strong influence on compressive circumferential stress in die insert but that the influence of the other design parameters is relatively weak.
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