• International Journal of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.226-232
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• 2020

Repetition of landing with visual control in sports and training is common, yet it remains unknown how landing with visual control affects postural stability and lower limb kinetics. The purpose of this study was to test the hypothesis that landing with visual control will influence on lower limb control for intrinsic dynamic postural stability. Kinematics and kinetics variables were recorded automatically when all participants (n=10, mean age: 22.00±1.63 years, mean heights: 177.27±5.45 cm, mean mass: 73.36±2.80 kg) performed drop landings from 30 cm platform. Visual control showed higher medial-lateral force, peak vertical force, loading rate than visual information condition. This was resulted from more stiff leg and less time to peak vertical force in visual control condition. Leg stiffness may decrease due to increase of perturbation of vertical center of gravity, but landing strategy that decreases impulse force was shifted in visual control condition during drop landing. These mechanism explains why rate of injury increase.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.48-52
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• 2007

Recently, the research of GPS receiver which uses the Software-Defined Radio(SDR) technique is being actively proceeded instead of traditional hardware-based receiver. The software-based GPS receiver indicates that the signal acquisition and tracking treated by the hardware-based platform are processed as the software technique through a microprocessor. In this paper, GPS software receiver is designed by using SDR technique and then the signal acquisition, tracking, and the navigation message decoding parts are verified through the PC-based simulation. Moreover, the efficient algorithms are developed about the signal acquisition and tracking parts in order to obtain the accurate pseudorange. Finally, the pseudorange is calculated through the relative channel delay received through the different satellite of L1 frequency band. GPS software receiver proposed in this paper will be included in the element of GPS/Galileo complex system of development target and will provide not only the method that verifies the performance for Galileo Sensor Station standard but also usability by providing various debugging environments.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.1
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• pp.40-44
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• 2013

The ball-shaped mobile robot, so called ballbot has single point contact on ground and low energy consumption in motion because of the reduced friction. In this paper, a new ballbot is presented, which has omnidirectional mobile platform inside of it as a driving system. Thus the ballbat has omnidirectional mobility without nonholonomic constraints. Kinematics and inverse kinematics of the ballbat is derived also in this paper.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.78-83
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• 2007

The paper focuses on the establishment of optimized bucket path planning and trajectory control designated for force-reflecting backhoe reacting to excavation environment, such as potential obstacles and ground characteristics. The developed path planning method can be used for precise bucket control, and more importantly for obstacle avoidance which is directly related to safety issues. The platform of this research was based on conventional papers regarding the kinematic model of excavator. Jacobian matrix was constructed to find optimal joint angles and rotation angles of bucket from position and orientation data of excavator. By applying Newton-Raphson method optimal joint angles and bucket orientation were derived simultaneously in the way of minimizing positional errors of excavator. The model presented in this paper was intended to function as a cornerstone to build complete and advanced path planning of excavator by implementing soil mechanics and further study of excavator dynamics together.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.435-442
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• 2003

In this paper, biomechanical aspects of dynamic대학교postural responses against forward perturbations were experimentally determined simultaneous measurements of joint angles, accelerations. EMG activations, center of pressure(CoP) movements and ground reaction forces(GRF), Thirteen young healthy volunteers, stood on a flat platform, were translated into the forward direction by an AC servo-motor at two separate velocities(0.1m and 0.2m/s). In order to recover postural balance against the forward perturbation, joint motions were observed in the sequence of the ankle dorsiflexion, the knee flexion and then the hip flexion during the later acceleration phase. Both acceleration patterns at the heel and the sacrum were shown the forward acceleration pattern during the later acceleration phase and early of constant velocity phase as increasing platform velocity, respectively. Tibialis anterior(TA) for the ankle dorsiflexion and biceps femoris(BF) for the knee flexion. the primary muscle to recover the forward perturbation, was activated during the half of acceleration phase. Ankle strategy was used for slow-velocity perturbation, but mixed strategy of both ankle and hip used for the fast-velocity perturbation. In addition, parameters of perturbation such as timing and magnitude influenced the postural response against the perturbation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.851-856
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• 2013

Recently, as the tactical environment has changedto one of network-centric warfare, where all components are connected through a network, much emphasis has been placed on the use of an artificial satellite for achieving high communication speeds. To provide a high-quality artificial satellite link, stabilization is very important in a platform. Previous stabilization control techniques used PI control, which is commonly used for vessels. However, for ground terminals that require a higher communication speed, the antenna should move faster to track an artificial satellite within a short period of time. Moreover, the terminals must be equipped with proper sensors and algorithms so that they can detect and compensate for external disturbances while tracking the artificial satellite. In this study, through the analysis of the dynamic model of an antenna system, a stabilization algorithm for ground terminals was proposed;this algorithm shows high isolation performance in the low-frequency range and includes $PI^2$ control.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.602-611
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• 2017

In railway systems, the exchange of information between running trains and wayside equipment is a very important role in various applications such as position detection and train control. Track circuits have been used as the medium for information transmission between trains and wayside. However, track circuits must be installed continuously along the track on the ground, resulting in an inevitable increase in installation and maintenance costs. One of the most promising solutions to reduce these costs is to mix continuous information transmission (via wireless communication) and discontinuous information transmission (via transponder). In this study, we designed antennas of railway high-speed transponder readers and tags for wireless power transmission, which can be used to transmit information from ground to high-speed trains with a maximum speed of 400km/h. We also verified system performance through computational simulation and prototyping.

• Korean Journal of Remote Sensing
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• v.36 no.5_3
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• pp.1013-1025
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• 2020

Unmanned Aerial Vehicle (UAV) platform is being widely used in disaster monitoring and smart city, having the advantage of being able to quickly acquire images in small areas at a low cost. Ground Control Points (GCPs) for positioning UAV images are essential to acquire cm-level accuracy when producing UAV-based orthoimages and Digital Surface Model (DSM). However, the on-site acquisition of GCPs takes considerable manpower and time. This research aims to provide an efficient and accurate way to replace the on-site GNSS surveying with three different sources of geospatial data. The three geospatial data used in this study is as follows; 1) 25 cm aerial orthoimages, and Digital Elevation Model (DEM) based on 1:1000 digital topographic map, 2) point cloud data acquired by Mobile Mapping System (MMS), and 3) hybrid point cloud data created by merging MMS data with UAV data. For each dataset a three-dimensional positional accuracy analysis of UAV-based orthoimage and DSM was performed by comparing differences in three-dimensional coordinates of independent check point obtained with those of the RTK-GNSS survey. The result shows the third case, in which MMS data and UAV data combined, to be the most accurate, showing an RMSE accuracy of 8.9 cm in horizontal and 24.5 cm in vertical, respectively. In addition, it has been shown that the distribution of geospatial GCPs has more sensitive on the vertical accuracy than on horizontal accuracy.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.3
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• pp.225-232
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• 2014

In this study, a cooperative UAV and UGV platform is proposed to obtain a wide range of visual information. The UAV recognizes a pattern marker on UGV and tracks the UGV without user control. It can provide wide range of visual information for a user in the UGV. The UGV by a user is controled equipped with an aluminum board. And the UAV can take off and land on the UGV. The UAV uses two cameras; one camera is used to recognize a pattern marker and another is used to provide a wide range of visual information to the UGV's user. It is guaranteed that the proposed visual-based approach detects and tracks the target marker on the UGV, and then lands well. The experimental results show that the proposed approach can effectively construct a cooperative UAV/UGV platform for obtaining a wide range of vision information.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2420-2426
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• 2015

This paper proposes an evolutionary optimization approach for optimal hopping of humanoid robots. In the proposed approach, the hopping trajectory is generated by a central pattern generator (CPG). The CPG is one of the biologically inspired approaches, and it generates rhythmic signals by using neural oscillators. During the hopping motion, the disturbance caused by the ground reaction forces is compensated for by utilizing the sensory feedback in the CPG. Posture control is essential for a stable hopping motion. A posture controller is utilized to maintain the balance of the humanoid robot while hopping. In addition, a compliance controller using a virtual spring-damper model is applied for stable landing. For optimal hopping, the optimization of the hopping motion is formulated as a minimization problem with equality constraints. To solve this problem, two-phase evolutionary programming is employed. The proposed approach is verified through computer simulations using a simulated model of the small-sized humanoid robot platform DARwIn-OP.