• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.771-782
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• 2017

This paper describes the development of a wearable robot to assist ankle power for the elderly. Previously developed wearable robots have generally used motors and gears to assist muscle power during walking. However, the combination of motor and reduction gear is heavy and has limitations on the simultaneous control of stiffness and torque due to the friction of the gear reducer unlike human muscles. Therefore, in this study, Mckibben pneumatic muscle, which is lighter, safer, and more powerful than an electric motor with gear, was used to assist ankle joint. Antagonistic actuation using a pair of pneumatic muscles assisted the power of the soleus muscles and tibialis anterior muscles used for the pitching motion of the ankle joint, and the model parameters of the antagonistic actuator were experimentally derived using a muscle test platform. To recognize the wearer's walking intention, foot load and ankle torque were calculated by measuring the pressure and the center of pressure of the foot using force and linear displacement sensors, and the stiffness and the torque of the pneumatic muscle joint were then controlled by the calculated ankle torque and foot load. Finally, the performance of the developed ankle power assistive robot was experimentally verified by measuring EMG signals during walking experiments on a treadmill.

• Journal of Internet of Things and Convergence
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• v.8 no.2
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• pp.35-40
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• 2022

In the agricultural environment, pesticide control requires a high risk of work and a high labor force for farmers. The effectiveness of pesticide control using unmanned aerial vehicles varies according to climate, land type, and characteristics of unmanned aerial vehicles. Therefore, an effective method for pesticide control by unmanned aerial vehicles considering the spraying conditions and environmental conditions is required. In this paper, we propose an efficient pesticide control system based on agricultural unmanned aerial vehicles considering the application conditions and environmental information for each crop. The effectiveness of the proposed model was demonstrated by measuring the drop uniformity of pesticides according to the change in altitude and speed after attaching the sensory paper and measuring the penetration rate of the drug inside the canopy according to the change in crop growth conditions. Experiment result, the closer the height of the UAV is to the ground, the more evenly the crops are sprayed, but for safety reasons, 2m more is suitable, and on average a speed of 2m/s is most suitable for control. The proposed control system is expected to help develop intelligent services based on the use of various unmanned aerial vehicles in agricultural environments.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.11
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• pp.445-452
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• 2017

Electric pole is a supporting beam used for power transmission/distribution which accelerometer are used for measuring a external force. The meteorological condition has various effects on the external forces of electric pole. One of them is the elasticity change of the aerial wire. It is very important to perform modelling. The acceleration sensor is converted into a pitch and a roll angle. The meteorological condition has a high correlation between variables, and selecting significant explanatory variables for modeling may result in the problem of over-fitting. We constructed high deviance explained model considering multicollinearity using the Generalized Additive Model which is one of the machine learning methods. As a result of the Variation Inflation Factor Test, we selected and fitted the significant variable as temperature, precipitation, wind speed, wind direction, air pressure, dewpoint, hours of daylight and cloud cover. It was noted that the Hours of daylight, cloud cover and air pressure has high explained value in explonatory variable. The average coefficient of determination (R-Squared) of the Generalized Additive Model was 0.69. The constructed model can help to predict the influence on the external forces of electric pole, and contribute to the purpose of securing safety on utility pole.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.1
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• pp.25-31
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• 2018

In this study, the differences of holding power according to the shape and weight distribution of concrete weight used in shellfish shell fishery were investigated through the experiments. To investigate the differences in shape, five bar-shaped concrete weights with the same length and different cross-sectional shapes were produced. The sectional shape of each weight was square, triangle, circle, small cross, and large cross (SQ, TR, CI, CR-S, CR-L). Ten rectangular parallelepiped weights with different bottom area and cross-sectional area were produced. To investigate the differences by the weight distribution, the holding power on the square model (SQ) with six 50 g weights at different positions was investigated. All the holding power was obtained by measuring the tensile force generated when the concrete weight was pulled at a constant speed on the sand. As a result, there were no differences in holding power between the ten rectangular weights. However, the experiment on weights with different cross-sectional shapes showed differences in holding power. The holding power was higher in the order of CR-L > CR-S > CI > TR > SQ. In the weight distribution test, the holding power was higher as the front side of the weight was heavier. Generally, the frictional force is the same even if the shape is different, when two objects have the same value in the weight and the roughness. On the other hand, it seems to have a large impact when the shape of the bottom is deformed in the course of pulling the object. Particularly, the larger the degree of protrusion like cruciform weights, the more the holding power increased while deeply digging the bottom. It is also likely that the holding power increases as the front weight increases.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.1-11
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• 2001

The geological characteristics of Korea are that we can encounter the rock layer only after 10m of excavation, methods to presume the rock pressure distribution of the rock layer is urgently needed. When using the existing empiric science of Terzaghi-Peck, Tschebotarioff to measure the rock pressure of the rock layer, underestimate the real strength because of the cohesion is ignored. Therefore calculating the horizontal sliding force of wedge block, which includes the dips and shear strength of discontinuities and surcharge load etc., think to be to getting a closer rock stress of the real rock pressure acting upon the earth structure in rock mass. This research use Coulomb soil pressure theory assuming that the backfill soil will yield wedge failure when it has cohesion, applying Prakash-Saran(l963), and then it uses equilibrium of force and shear strength $\tau$=c+$\sigma$tan $\Phi$ of the cliscontinuities. Analyzing shear strength and dips of cliscontinuities using calculated theory according to the status of discontinuities aperture, we were able to find out that because the cohesion and friction angle of the rock layer itself is large enough, how the dip directions and dips facing the excavation face is the only factor deciding whether or not the rock stress is applied. The evaluated theory of this research should be strictly estimated, so that the many parameters such as c, $\Phi$value, types and structures of rock class, excessive lateral pressure, dynamic load, earthquake, needed later when calculating shear strength of discontinuities and especially the ground water effect acting on rock layer should be coumpted with many measuring data achieve at the insite to study the application.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.5
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• pp.625-631
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• 2011

The passive control of fluid force acting on a square prism near a plane wall was studied by attaching horizontal splitter plate on the corner of the prism. The width of the splitter plate was 10% of the square width. The experiments were performed by measuring of fluid force on the prism and by visualization of the flow field using PIV. The experimental parameters were the attaching position and the space ratios G/B between the prism and wall. The flow between the prism and wall was remarkable and Karman vortex in the wake of the prism was considerable in the space ratio over 0.4. The point of inflection of average lift coefficient and Strouhal number on the prism were represented at the space ratio G/B=0.4 for the prototype prism and G/B=0.6 for the prism having horizontal splitter plate. The drag of the prism was reduced average 4.5% with the space ratios by attaching the horizontal splitter plate at the rear and lower corner on the prism. In this case, the size of the separated region on the upside of the prism was smaller than that of prism without the splitter plate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.435-443
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• 2017

The Characteristics of the flowfields of a square prism having a small square prism were investigated by measuring of lift and drag on the square prism and visualizing the flowfield using PIV. The experimental parameters were the width ratios(H/B=0.2~0.6) of small square prisms to the prism width and the gap ratios (G/B=0~3) between the prism and the small square prism. The drag reduction rate of the square prism initially increased and then decreased with the G/B ratio for the same H/B ratio, and increased with the H/B ratio for the same G/B ratio. The maximum drag reduction rate of 98.0% was observed at H/B=0.6 and G/B=1.0. The lift reduction rate of the square prism was not affected by the width and gap ratios; the total average value was approximately 66.5%. In case of a square prism having a small square prism, the stagnation regions were represented in the upstream and downstream sides of the square prism.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.965-972
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• 2016

This paper presents results of flight experiments on a navigation algorithm including multiplicative extended Kalman filter for estimating attitude of the guided munition. The filter describes orientation of aircraft by data fusion with low-cost sensors where measurement update is done by multiplication, rather than addition, which is suitable for quaternion representation. In determining attitude from vector observations, the existing approach utilizes a 3-axis accelerometer as a 2-axis inclinometer by measuring gravity to estimate pitch and roll angles, while GNSS velocity is used to derive heading of the vehicle. However, during accelerated maneuvers such as coordinated flight, the accelerometer provides inadequate inclinometer measurements. In this paper, the measurement update process is newly defined to complement the vulnerability by using different vector observations. The acceleration measurement is considered as a result of a centrifugal force and gravity during turning maneuvers and used to estimate roll angle. The effectiveness of the proposed method is verified through flight experiments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.56-62
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• 2018

The bus bar is an electrical connection widely used for the power supply of skyscrapers and power distribution and industrial equipment electrical panels in industrial plants. There are various materials to be considered in the design of the bus bar, such as material based on the use environment, the sectional area according to the power capacity, the length of the surface circumference, and the tightening method. Even with a bus bar manufactured to a size of sufficient power capacity in the design, if the actual tightening is incorrect, it may lead to fire due to deterioration. For these reasons, a variety of research on the temperature rise of the electrical contact point has continued. However, the temperature rise of the contacts is a consequence of the result, not a direct cause. In this paper, the influence of contact resistance on the fastening force and the overlapping section of the bus bar are investigated by measuring the change in resistance from building the specimen. A total of eight bus bar specimens were manufactured and measured. Resistance was measured by varying the clamping force and the interval between overlapping sections when the specimens were crossed. We propose a safe power connection model by analyzing the contribution of these factors to the actual contact resistance change.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.571-577
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• 2018

A gyratory compactor was developed to reflect the field compaction roller, which is commonly used in road construction. Unlike the compaction of the proctor using a conventional impact load, the gyratory compactor simulated the field roller compaction characteristics using the compressive force by the roller weight and the shear force through the rotation of a roller. The purpose of this study was to evaluate the shear stress and density change characteristics during compaction, which are difficult to obtain in the existing compaction process of the proctor, and to utilize it as a basic data for road design. The compaction characteristics of sand and subgrade soils were also analyzed and evaluated using the gyratory compactor. The compaction characteristics obtained using the gyratory compaction are basically the number of gyrations, height of the specimen, compaction density, void ratio, degree of saturation, and shear stress. As the number of gyrations increased, the height of the specimen decreased, the compaction density increased, the void ratio decreased, the degree of saturation increased, and the shear stress tended to increase. The shear stress of the compacted specimens started at 200 kPa in the initial stage of compaction and increased to approximately 330 to 350 kPa at 50 gyrations. The compaction density, degree of saturation and shear stress tended to increase with increasing water content in the same specimens. Compaction using turning compaction has the advantage of measuring the physical properties required for road design, such as density and shear stress, so that more engineering road design will be possible if it is reflected in road design.