• 한국체육학회지인문사회과학편
• /
• 제54권1호
• /
• pp.515-525
• /
• 2015

이 연구는 태권도학과 시범단 8명과 일반학생 8명을 대상자로 선정을 하여 태권도 발차기 동작 시 숙련도에 따른 체간과 하지근육의 근 활성도 비교를 목적으로 실시되었다. 태권도 앞차기, 돌개차기, 뒤후려차기 동작 시 이용되는 주요근육을 표면근전도를 이용하여, 무릎을 들어올리는 동작(P1)과 발을 차는 동작(P2)구간별로 근 활성도를 비교분석하여 다음과 같은 결론을 얻었다. 앞차기 동작 시에는 비숙련자들은 체간의 하부복직근의 활성도와 차는발의 대퇴이두근 및 지지발의 내측광근 및 외측비복근의 활성도가 숙련자보다 높고, 허리세움근 2개의 근활성도는 낮은 것으로 나타났다. 돌개차기(턴차기) 동작 시 회전동작에서는 숙련자들의 대퇴이두근과 척추근의 활성도가 비숙련자보다 높고, 차는동작에서는 하지 근 활성도는 대퇴이두근의 활성도가 높게 나타났다. 뒤후려차기 동작 시 비숙련자들의 차는발 외측비복근과 지지발의 대퇴근육 3개의 근 활성도가 숙련자보다 높게 나타났다. 이상의 결과를 종합해 보면, 숙련자들은 회전동작에서 체간을 사용하며 빠르게 회전하고 차는 발의 근 활성도가 높지 않지만, 비숙련자들은 차는발과 지지발에 근 활성도가 높게 나타났으며, 이는 차는 동작에서 균형을 유지하기 위하여 체간근육보다는 하지에 힘이 들어가 비효율적인 동작을 하는 것으로 나타났다.

• 대한조선학회지
• /
• 제21권1호
• /
• pp.3-12
• /
• 1984

Up to now, it has been common to treat the maneuvering motion of a ship as a 3-degree-freedom motion i.e. surge, sway and yaw on the sea surface, for the simplicity and mathematical calculation, and it is quite acceptable in the practical point of view. Meanwhile, considering the maneuverability of a ship under the special conditions such as in irregular waves, in wind or at high speed with small GM value, it is required that roll effect must be considered in the equation of ship motion. In this paper the author tried to build up the 4-degree-freedom motion equation by adding roll. And then, applying the M.M.G.'s mathematical model and with captive model test results the roll-coupled hydrodynamic derivatives were found. With these the author could make some simulating program for turning and zig-zag steering. Through the computer simulations, the effect of roll to the ship maneuver became clear. The effect of the wind force to the maneuverability was also found. Followings are such items that was found. 1) When roll is coupled in the maneuvering motion, the directional stability becomes worse and the turning diameter becomes smaller as roll becomes smaller as roll becomes larger. 2) When maneuver a ship in the wind, the roll becomes severe and the directional stability becomes worse. 3) When a ship turns to the starboard side, the wind blowing from 90 degree direction to starboard causes the largest roll and the largest turning diameter, and the wind from other direction doesn't change the turning diameter. 4) When a ship is travelling with a constant speed with rudder amidship, if steady wind blows from one direction, the ship turns toward that wind. This phenomenon is observed in the actual seaways.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.923-928
• /
• 2003

This paper presents the motion control of a mobile robot with arc sensor for lattice type welding. Its dynamic equation and motion control method for welding speed and seam tracking are described. The motion control is realized in the view of keeping constant welding speed and precise target line even though the robot is driven along a straight line or comer. The mobile robot is modeled based on Lagrange equation under nonholonomic constraints and the model is represented in state space form. The motion control of the mobile robot is separated into three driving motions of straight locomotion, turning locomotion and torch slider controls. For the torch slider control, the proportional integral derivative (PID) control method is used. For the straight locomotion, a concept of decoupling method between input and output is adopted and for the turning locomotion, the turning speed is controlled according to the angular velocity value at each point of the comer with range of $90^{\circ}$ constrained to the welding speed. The proposed control methods are proved through simulation results and the results have proved that the mobile robot has enough ability to apply the lattice type welding line.

• 제어로봇시스템학회논문지
• /
• 제17권6호
• /
• pp.513-520
• /
• 2011

This paper presents the motion planning of robotic vehicles for the path tracking and the obstacle avoidance. To follow the given path, the vehicle moves through the turning radius obtained through the pure pursuit method, which is a geometric path tracking method. In this paper, we assume that the vehicle is equipped with a 2D laser scanner, allowing it to avoid obstacles within its sensing range. The turning radius for avoiding the obstacle, which is inversely proportional to the virtual force, is then calculated. Therefore, these two kinds of the turning radius are used to generate the steering angle for the front wheel of the vehicle. And the vehicle reduces the velocity when it meets the obstacle or the large steering angle using the potentials of obstacle points and the steering angle. Thus the motion planning of the vehicle is done by planning the steering angle for the front wheels and the velocity. Finally, the performance of the proposed method is tested through simulation.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.1025-1028
• /
• 2002

In this paper, a micro-turning lathe is introduced for micro machining of aluminum rod. To give feed motion, stepwise motion[2] actuators are used instead of the conventional inchworm mechanism. These are consisted of two Piezoelectric ceramics; one is for feeding the slider, and the other is for clamping the slider in the guide way of the body. The guide is V-form. The linearity and positional accuracy of the actuators is good enough far high precision motion. Since the system is more compact than the conventional system using three Piezoelectric ceramics, it is applicable for the micro-machine or MEMS unit. To fabricate the lathe, a small spindle unit with ball bearings of diameter of 10 millimeter is built-up on the top the slider. The motion is feed backed with miniaturized linear encoder attached each axis slider. The diamond tool bite is used for cutting tool. The machining is tried to make small diameter rod. The possible diameter that can be machined in this machine is presented as well as chip formation, surface roughness, and machinability.

• 한국항해학회지
• /
• 제3권1호
• /
• pp.1-17
• /
• 1979

It is very important for both naval architects and ship's officers to know the maneuvering characteristics of their ships. As the abilities of a rudder which controlls a ship can be determined clearly by analyzing the results of Kempf's zig-zag maneuver and directional stability of a ship also known by Dieudonn spiral maneuver, the importance of turning test which takes much time is recently apt to be neglected. But because the test can be executed comparatively more simply than any other maneuvering tests, it gives some informations on the directional stability, and turning characteristics may be expressed simply by the results of the test, it is still often performed. In this paper several assumptions are made to simplify the turning motion of a ship. The equations of initial transient phase, the radius ofsteady turning circle, and the center of the steady turning point are derived by using the hydrodynamic derivatives. And then the approximate method of drawing the turning circle geometrically is suggested.

• 해양환경안전학회:학술대회논문집
• /
• 해양환경안전학회 2002년도 추계학술발표회
• /
• pp.127-134
• /
• 2002

Ship operators are used to dredge anchor for the collision avoidance or safety of ship handling in a harbour or narrow channel. This paper clarifies the technique using tile anchor dredging known as a common sense for the seafarers. A mathematical model at low speed range has been established for the estimation of ship motion under the assumed environment , simulate the advance speed , and turning ability under the anchor dredging or not. The results shows good agreement with the conventional seamanship and their experiences as follows. Ahead speed used the anchor dredging is slower(speed reduction ratio:40%) than the normal ahead speed and the stopping distance is shorter (distance reduction ratio:40%)than the normal ahead distance without the anchor dredging. Turning speed used anchor dredging is slower(speed reduction ratio:72%)than the normal ahead speed and the tactical diameter is shorter(distance reduction ratio:24%)than the diameter by the normal turning without the anchor dredging.

• 한국항해항만학회지
• /
• 제33권9호
• /
• pp.603-608
• /
• 2009

In this paper, a 3m-class free running model ship will be introduced with its manoeuvring performance experiments. The results of turning circle test and zig-zag test will be explained. The developed system are equipped with GPS, main control computer, wireless LAN, IMU (Inertial Measurement Unit), self-propulsion propeller and driving rudder. Its motion can be controlled by RC (Radio Control) and wireless LAN from land based center. Automatic navigation is also available by pre-programmed algorithm. The trajectory of navigation can be acquired by GPS and it provides us with important data for ship's motion control experiments. The results of manoeuvring performance experiment have shown that the developed free running model ship can be used to verify the test of turning circle and zig-zag. For next step, other experimental researches such as ship collision avoidance system and automatic berthing can be considered in the future.

• Journal of Biosystems Engineering
• /
• 제43권4호
• /
• pp.273-284
• /
• 2018

Purpose: Conventional headland turning typically requires repeated forward and backward movements to move the farming equipment to the next row. This research focuses on developing an upland agricultural robot with an optimized headland turning mechanism that enables a $180^{\circ}$ turning positioning to the next row in one steering motion designed for a two-wheel steering, four-wheel drive agricultural robot named the HADA-bot. The proposed steering mechanism allows for faster turnings at each headland compared to those of the conventional steering system. Methods: The HADA-bot was designed with 1.7-m wide wheel tracks to travel along the furrows of a garlic bed, and a look-ahead path following algorithm was applied using a real-time kinematic global positioning system signal. Pivot turning tests focused primarily on accuracy regarding the turning radius for the next path matching, saving headland turning time, area, and effort. Results: Several test cases were performed by evaluating right and left turns on two different surfaces: concrete and soil, at three speeds: 1, 2, and 3 km/h. From the left and right side pivot turning results, the percentage of lateral deviation is within the acceptable range of 10% even on the soil surface. This U-turn scheme reduces 67% and 54% of the headland turning time, and 36% and 32% of the required headland area compared to a 50 hp tractor (ISEKI, TA5240, Ehime, Japan) and a riding-type cultivator (CFM-1200, Asia Technology, Deagu, Rep. Korea), respectively. Conclusion: The pivot turning trajectory on both soil and concrete surfaces achieved similar results within the typical operating speed range. Overall, these results prove that the pivot turning mechanism is suitable for improving conventional headland turning by reducing both turning radius and turning time.

• 한국운동역학회지
• /
• 제14권1호
• /
• pp.117-131
• /
• 2004

The foreign superior players and national team players' turning phase was measured, compared and analyzed to help the representative players improve the skill of turn. The underwater video camera used to analyze and evaluate the representative players' skill of turn in detail and the result is as follows. 1. The record for the phase of turn was similar to the rank of the last record. The improvement of the skill of turn was required because Korean players' record was lower than the foreign players' one. In case of 200m events the 1st turn was the fastest and it took more time as the turn is repeated. 2. It shows that the preparation phase and turing motion cause the difference between the players and within one player. 3. The horizontal movement of center of gravity moves to turning point slowly in the preparation phase, does not move nearly in the turning phase and increase again in the propulsion phase. Good record has short time for turn phase. The result means that the shorten the turning phase is the most important factor. Therefore the preparation for this is required. The vertical movement is maintained or increase a little and then move to from the turning phase. 4. The characteristic of horizontal velocity in center of gravity is that there is any big changes at the preparation phase, the faster velocity is found from the better record and the accelerating time is fast at the propulsion phasen. The wrong motion is made by not using the swimming velocity for fuming and waiting and more time is required by this. 5. The angle of knee when the player touch the turning point is 106.22-135.56 and the maximum angle of knee during the driving after the touch of tuning point is full extension. The size of maximum angle of knee did not match with the required time of propulsion phase. It seems that the individual difference is big when the players touch the turning point the angle of knee and the research for the individual angle which can reveal the maximum power should be carried out. The national team player's skill for the him is behind the foreign players' one and a lot of problems were found. It shows that the players could not practice the skill for turn during the training. The 1st reason for it is the various facilities like underwater window or analyzing equipment like underwater camera with which the coaches can teach and correct the players' detailed skill. It is need to evaluate the players' detailed skill exactly and correct it by objective data to complete the good skill in the future. In this regard, the investment for the facility is necessary.