• Journal of Biosystems Engineering
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• v.32 no.2 s.121
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• pp.91-96
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• 2007

In this study, a prototype remote controlled weeder using solar module was developed and the evaluations of weeding, side walking and weeding performance were conducted to see if actual application was feasible in the paddy field. When traveling, the loss electric current was 8 to 15 A depending on operating and soil conditions. The average traveling speed was 0.25 m/s and the average slippage was 18%. When it side walked row by row, electric current consumption was 7 A on the average. When wheel rotors line went initially up and last down, electric current consumption was 12 to 15 A due to soil resistance. Electric current consumption when shifting wheel rotors line was less than 5 A due to no resistance. Field efficiency was 105 min/10a based on the test field. Operation was able to be done for 4.16 hours continually by 52 AH battery based on 300 W average maximum power consumption and 4.6 hours under sunny day considering solar module.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.140-148
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• 2017

Accidents involving wheelchair accessible vehicles have been frequently occurring since the introduction of these vehicles in the Korean market. However, detailed regulations, which are required to ensure the safety of the wheel-chair occupants, are unavailable. In this study, both domestic and international vehicle safety regulations are analyzed in order to select the regulations that are similar to the transportation environment of Korea. Sled tests with an actual wheel-chair accessible vehicle were carried out based on the analyzed regulation requirements, as well as the values of the HIC, belt loads, dummy movements, and wheelchair movements. The test results showed that the movements of the dummy and the wheelchair did not meet the criteria of the regulation due to the improper positioning of the restraint systems.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.2
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• pp.84-88
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• 2016

This study evaluated the structural safety of a heavy-duty integrated machine for grinding wheel forming. Structural analysis was performed to evaluate the structural safety of the base. The base was designed by dividing the single base and detachable base. The analysis conditions were applied to the own weight and the load of component parts. From the structural analysis results, although the stress of the detachable base was decreased, the amount of deformation was increased. If the deformation of the detachable base decreases, it is expected to be safer than the single base.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.2
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• pp.184-191
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• 2009

The common requirements of rough terrain mobile robots are long-term operation and high mobility in rough terrain to perform difficult tasks. In rough terrain, excessive wheel slip could cause an increase in the amount of dissipated energy at the contact point between the wheel and ground or, even more seriously, the robot could lose all mobility and become trapped. This paper proposes a traction control algorithm that can be independently implemented to each wheel without requiring extra sensors and devices compared with standard velocity control methods. The proposed traction algorithm is analogous to the stick-slip friction mechanism. The algorithm estimates the slippage of wheels by angular acceleration change, and controls the increase or decrease state of torque applied to wheels Simulations are performed to validate the algorithm. The proposed traction control algorithm yielded a 65.4% reduction of total slip distance and 70.6% reduction of power consumption compared with the standard velocity control method.

• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.231-243
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• 2021

In this paper, a dynamic response mapping model of the wheel-rail system is established by using the support vector regression (SVR) method, and the hierarchical safety thresholds of the subgrade void are proposed based on the reliability theory. Firstly, the vehicle-track coupling dynamic model considering the subgrade void is constructed. Secondly, the subgrade void area, the subgrade compaction index K30 and the fastener stiffness are selected as random variables, and the mapping model between these three random parameters and the dynamic response of the wheel-rail system is built by using the orthogonal test and the SVR. The sensitivity analysis is carried out by the range analysis method. Finally, the hierarchical safety thresholds for the subgrade void are proposed. The results show that the subgrade void has the most significant influence on the carbody vertical acceleration, the rail vertical displacement, the vertical displacement and the slab tensile stress. From the range analysis, the subgrade void area has the largest effect on the dynamic response of the wheel-rail system, followed by the fastener stiffness and the subgrade compaction index K30. The recommended safety thresholds for the subgrade void of level I, II and III are 4.01㎡, 6.81㎡ and 9.79㎡, respectively.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.2
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• pp.53-59
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• 2022

In this paper, a mobile robot capable of remote control is designed in consideration of the user's various work environments. Specifically, a mobile remote work robot that moves in a predetermined direction and can perform a series of tasks in synchronization with the user's hand movements, and a control system and control method for controlling the robot were proposed. It was implemented using a robot hand and a wheel for movement to assist in tasks such as transporting dangerous goods or heavy goods. In order to evaluate the performance of the developed robot, the maximum weight that can be carried by the robot hand and the movable inclination of the robot were tested, and the test evaluation results satisfied most of the targeted design specifications.

• The Journal of Korea Robotics Society
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• v.18 no.2
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• pp.143-154
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• 2023

In this study, a fast motion planning method for the swing motion of a 6x6 wheel-legged robot to traverse large obstacles and gaps is proposed. The motion planning method presented in the previous paper, which was based on trajectory optimization, took up to tens of seconds and was limited to two-dimensional, structured vertical obstacles and trenches. A deep neural network based on one-dimensional Convolutional Neural Network (CNN) is introduced to generate keyframes, which are then used to represent smooth reference commands for the six leg angles along the robot's path. The network is initially trained using the behavioral cloning method with a dataset gathered from previous simulation results of the trajectory optimization. Its performance is then improved through reinforcement learning, using a one-step REINFORCE algorithm. The trained model has increased the speed of motion planning by up to 820 times and improved the success rates of obstacle crossing under harsh conditions, such as low friction and high roughness.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.84-91
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• 2012

This study evaluated three forces (lifting, pushing and twisting) required to maneuver the single-wheel barrows according to handle height, width, horizontal angle and vertical angle. The four independent variables were varied in two levels. Handle height was varies in two levels : 'knuckle height (KH)' and 'KH + 0.1 ${\times}$ stature'. The two handle widths were '1.5 ${\times}$ shoulder width (SW)' and '1.75 ${\times}$ SW'. Two angles of $0^{\circ}$ and $15^{\circ}$ were used for horizontal and vertical angles. The 24 factorial design was used in the experiment. Twelve healthy male students (undergraduate and graduate) participated in the experiment. Subjects exerted three forces (pushing, lifting, and twisting clockwise) in each experimental condition. The order of 16 treatment conditions was determined randomly. Results showed that the effects of the four factors were different according to three forces. While lifting and twisting forces were higher in 'knuckle height', the pushing force was higher in 'KH + 0.1 ${\times}$ stature' (p < 0.05). Lifting and pushing forces showed higher values in the horizontal angle $0^{\circ}$ than in $15^{\circ}$. Handle width and vertical angle showed no statistically significant main effects on three forces (p > 0.05). Results of this study could be used as basic data for the ergonomic design of handle variables of one- or two-wheel barrows.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.19-28
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• 2007

In this study, a nonlinear 2 degree of freedom mathematical model has been developed for impact analysis of the nose landing gear of a light aircraft which is composed of an wheel & tire, an Oleo-pneumatic shock strut and the castering wheel fork for the differential braking steering, and then the response of impact is computed using a numerical method. The mathematical model of a nose landing gear contains nonlinear characteristics which are an impact load - deflection property of a tire and internally frictional forces between an inner surface of an upper cylinder and a bearing of a lower rod due to side forces like the declined angle of strut, the moment due to an wheel fork, the side drag due to a steering and it is computed using the 4th-order Runge-Kutta method. The comparison process between analytical results and experimental results of the other proven nose landing gear is carried out to verify the mathematical model.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.134-141
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• 2014

Mobile robots use various sensors for navigation such as wheel encoder, vision sensor, sonar, and laser sensors. Dead reckoning is used with wheel encoder, resulting in the accumulation of positioning errors. For that reason wheel encoder can not be used alone. Too much information of vision sensors leads to an increase in the number of features and complexity of perception scheme. Also Sonar sensor is not suitable for positioning because of its poor accuracy. On the other hand, laser sensor provides accurate distance information relatively. In this paper we propose to extract the angular information from the distance information of laser range finder and use the Kalman filter that match the heading and distance of the laser range finder and those of wheel encoder. For laser scanner with one feature point error may increase much when the feature point is variant or jumping to a new feature point. To solve the problem, we propose to use two feature points and show that the positioning error can be reduced much.