• Korean Journal of Applied Biomechanics
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• v.24 no.2
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• pp.173-180
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• 2014

The purpose of this study was to investigate the effect of combined exercise on injury risk factors of lower extremity during landing. Ten sports talented athletes participated in this study. Sports talented athletes participated in a combined exercise (sports talented exercise, coordination) for 16 weeks. A three-dimensional motion analysis was performed using eight infrared cameras (sampling rate of 100 Hz), one force plate, and electromyography system (sampling rate of 1000 Hz) during landing. Kinetic, and kinematics analysis including average impulsive force, angle of lower extremity, vertical stiffness, onset of muscle activation were calculated by Matlab2009a software. Paired t-test was performed at alpha=.05. The average impulsive force in landing phase was not statistically significant (t=-.748, p=.474). The hip joint angle was more decreased in post test compared to pre test (E1: t=2.682, p=.025, E2: t=5.609, p=.000, E3: t=2.538, p=.032). The knee joint (E1: t=-.343, p=.739, E2: t=1.319, p=.220, E3: t=.589, p=.570) and ankle joint (E1: t=.081, p=.937, E2: t=.784, p=.453, E3: t=.392, p=.704) angle were tended to decrease after combined exercise. The vertical stiffness was tended to decrease after combined exercise (t=1.972, p=.080). Onset of quadriceps femoris (t=.698, p=.503) and medial gastocnemius (t=1.858, p=.096) were tended to be faster than biceps femoris (t=-.333, p=.747) after combined exercise. Although thses findings were not statistically significant except on a hip joint angle, risk factors of lower extremity such as joint angle, vertical stiffness and onset of quadriceps femoris, medial gastrocnemius were positively changed after the combined exercise but an additional training for improved onset of biceps femoris would be required in the future.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.4
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• pp.623-640
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• 2017

The full nonlinear equations of an unmanned aerial vehicle ground taxiing mathematical dynamic model are built based on a type of unmanned aerial vehicle data in LMS Virtual.Lab Motion. The flexible landing gear model is considered to make the aircraft ground motion more accurate. The electric braking control system is established in MATLAB/Simulink and the experiment of it verifies that the electric braking model with the pressure sensor is fitted well with the actual braking mechanism and it ensures the braking response speediness. The direction rectification control law combining the differential brake and the rudder with 30% anti-skid brake is built to improve the directional stability. Two other rectifying control laws are demonstrated to compare with the designed control law to verify that the designed control is of high directional stability and high braking efficiency. The lateral displacement increases by 445.45% with poor rectification performance under the only rudder rectifying control relative to the designed control law. The braking distance rises by 36m and the braking frequency increases by 85.71% under the control law without anti-skid brake. Different landing conditions are simulated to verify the good robustness of the designed rectifying control.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2335-2342
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• 2014

If you want to use the unmanned quad rotor for emergency information provision and information about the traffic situation of real-time and moving information is included in the car to help in emergency vehicle operation of the city and in the distribution future innovation the need to consider to have enough safety of the use of silent quad rotor. Therefore, in this study, the unmanned quad rotor system research of safe landing control from the center for the improvement of safety of unmanned quad rotor system you have a motor of four, has taken a good structural balance system based on the dynamic model and motion considering the nonlinear characteristics, and attempts to proceed via non-linearity and system disturbances, tough Fuzzy controller, and analyzed through a computer simulation result.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.301-309
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• 2018

The aim of this study was to investigate the relationship between the neurocognitive ability and the risk factors of non-contact anterior cruciate ligament injuries during landing in female recreational athletes. Thirty-two female athletes participated in computerized neurocognition test and motion analysis for drop vertical jump. Pearson's linear correlation analysis was performed to analyze the relationship between the raw scores of neurocognition test and biomechanical variables including 3D joint angle, moment, power, vertical ground reaction force, loading rate, and support time. There were correlations between the scores of neurocognition test and biomechanical variables as high the neurocognition score, it also increase landing strategies were used to maintain posture of the lower extremity. Therefore, the neurocognitive test might be used as a good screening method to detect the risk factors before injury.

• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.173-179
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• 2011

This study aims to analyse difference in biomechanical factors between dominant legs and recessive ones according to muscular imbalance during drop landing targeting talented children in sports. The subjects of the study were ten primary students who are attending to Sports Program for Talented Children organized by C university (age: $12.28{\pm}0.70$ year, height: $1.52{\pm}0.11$ m, and weight: $45.2{\pm}4.9$ kg). Strength legs were classified into dominant side and strengthless legs were classified into non-dominant legs. For three-dimensional analyses of the data collected, 6 video cameras(MotionMaster200, Visol, Korea) were used. To analyse ground reaction force, two force platforms(AMTI ORG-6, MA) were used and to analyse electromyograghy a 8-channeled wireless Noraxon Myoresearch made in USA was used at 1000 Hz for sampling. As a result, it was discovered that the dominants legs controlled knee bending motions more stably than strengthless legs as the maximum vertical ground reaction force was significantly high in dominant legs(p<.05), and joint moment of knee joints of the dominant legs was high(p<.05). Therefore, this study suggested that injury prevention program focusing on muscular balance as well as the existing sports programs for talented children should be developed based on results of the study and it is expected that the results will be useful for improvement of sports programs for talented children.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.6
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• pp.536-541
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• 2015

In this paper, we propose a the image-based automatic flight control system for the mini drone. Automatic flight system with a camera on the ceiling and markers on the floor and landing position is designed in an indoor environment. Images from the ceiling camera is used not only to recognize the makers and landing position but also to track the drone motion. PC sever identifies the location of the drone and sends control commands to the mini drone. Flight controller of the mini drone is designed using state-machine algorithm, PID control and way-point position control method. From the, The proposed automatic flight control system is verified through the experiments of the mini drone. We see that known makers in environment are recognized and the drone can follows the trajectories with the specific ㄱ, ㄷ and ㅁ shapes. Also, experimental results show that the drone can approach and correctly land on the target positions which are set at different height.

• International Journal of Automotive Technology
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• v.8 no.4
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• pp.429-436
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• 2007

In this study, we improved control performance of an EMV (electromechanical valve) system using a PM/EM (permanent magnet/electromagnet) hybrid EMA (electromagnetic actuator) and showed the feasibilities of both soft landing and fast transition of the EMV system using a simple PID control. The conventional EMV systems using only EM show significant nonlinear characteristics. Therefore, it is very difficult to control the valve position and several complex control schemes are used. This paper focused on the control performance improvement using a PM/EM hybrid actuator. In particular, a PM is used as a key design parameter such as a bias current of a magnetic bearing in order to improve the linear characteristic of the actuator, although most PM/EM hybrid actuators use a PM as a power saver during valve-open and -closed states. First, a FE (finite element) analysis was performed to confirm its linear static force characteristics. Then, both a test rig and a valve control system were built in order to prove experimentally the control performance improvement of the actuator. Finally, feasibilities of both soft landing and fast transition of the system were shown experimentally through gain-scheduled PID (proportional derivative integral) control.

• Journal of the Korean Applied Science and Technology
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• v.37 no.2
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• pp.296-302
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• 2020

The purpose of this study was to assess knee joint loading in the target knee during a golf swing compared to loading rates of high impact activities such as cutting and drop landings. Nine healthy competitive golfers completed golf swings with the target foot both straight and externally rotated 30 degrees, as well as drop landings and cutting maneuvers. Motion capture data was collected at 240 Hz and ground reaction force data was collected at 2400 Hz. The frontal and transverse knee moments were examined using repeated measures ANOVA through SPSS. The abduction moments were higher in golf swings as compared to the other high impact activities (p=.010), while the external rotation moments were lower (p=.003). There were no significant differences between externally rotated and neutral golf swings. These results suggest moments applied to the knee during a golf swing are similar to those applied during a high impact activity.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.157-167
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• 2007

The purpose of this study was to analyze kinematic techniques in the woman's 100m hurdle. In order to find the kinematic parameters, a 3-D video system for kinematic analysis-kwon3d 3.1(Kwon3D Motion Analysis Program Version 3.1)-was used. Eight JVC video cameras(GR-HD1KR) were used to film the performance of Lee Yeon-Kyoung at a frame rate of 60fields/s. The kinematic characteristics from the first hurdle to last hurdle were analyzed at the clearing hurdle spots such as distance, velocities, heights and angles. The real-life three-dimensional coordinates of 20 body landmarks during each phases were collected using a Direct Linear Transformation procedure. After analyzing the kinematic variables in the 100m hurdle run, the following conclusion were obtained; Lee Yeon-Kyoung had to maintain constant stride lengths between hurdles and increase takeoff distance before clearance and shorter landing distance after clearance. She also had to hit the correct takeoff point in front of the hurdle and extend the lead leg at the moment of landing in order to minimize the loss of velocity. She had to sprint between hurdles as fast as possible over 8m/s and run powerful first stride and shortened third stride preparing for the following hurdle clearances.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.56-66
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• 2013

Weight reduction of the VTHL / TSTO type of the reusable launch vehicles using RBCC engines are investigated. To predict weight and thrust of the vehicles, equations of motion are analyzed. Analysis results are compared with specifications of existing launch vehicles for validations. For the mission of inserting 2.5 ton payload to 200 km circular orbit, the case A, which uses the RBCC engine in the 1st stage shows smaller weight than the case B, which uses the RBCC engine in the 2nd stage. The weight of the case A shows only 25.8% of a existing rocket launch vehicle's weight.