• 한국항해항만학회지
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• 제42권2호
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• pp.87-96
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• 2018

A trajectory control system plays an important role in controlling motions of marine vehicle when a series of way points or a path is given. In this paper, a sliding mode control (SMC)-based trajectory tracking controller for marine vehicles is presented. A small-sized unmanned ship is considered as a control object. Both speed and heading angle of a ship should be controlled for tracking control. The common point of related researches was to separate ship's speed and heading angle in control methods. In this research, a new control law from a general sliding mode theory that can be applied to MIMO (multi input multi output) system is derived and both speed and heading angle of a ship can be controlled simultaneously. The propulsion force and rudder force are also applied in modeling stage to achieve accurate simulation. Disturbance induced by wind is also tackled in the dynamics considering robustness of the proposed control scheme. In the simulation, we employed a way-point method to generate ship's trajectory and applied the proposed control scheme to ship's trajectory tracking control. Our results confirmed that the tracking error was converged to zero, thus demonstrating the effectiveness of the proposed method.

• 수산해양기술연구
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• 제28권1호
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• pp.10-20
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• 1992

The new course distances of a ship are considered to be the indices to indicate directly her abilities of course altercation. Generally, they have long been calculated by using the maneuvering indices obtained from her Z test. However, at sea actually the maneuvering indices can not sometimes be obtained according to ship's condition or circumstances and the new course distances can not be calculated. To find out other method to calculate the new course distances, in this paper the author analyzed them from a viewpoint of ship motion, and worked out a numerical formula to calculate them easily, using the data of ship's heading test. In order to check whether the presented method is applicable to actual ships or not, the experiment by them were also performed. The results obtained are summarized as follow: 1. The mean difference of the distance between two new course distances by the heading test and the maneuvering indices of the experimental ship was about 0.98% values of the ones by the maneuvering indices, when her heading were 10。, 20。 and 30。, using the rudder angle of 15。. These new course distances were therefore found to be almost same in values of the distance. 2. The mean difference of the distance between two new course distances by the heading test and the observation of experimental ship was about 1.16% values of the ones by the observation, when her headings were 10。, 20。 and 30。, using the rudder angle of 15。. These new course distances were therefore found to be almost same in values of the distance. 3. It is confirmed that the new course distances can be calculated easily by using the method of ship's simple heading test, without the observation or using the maneuvering indices. 4. It is considered to be helpful for the safety of shiphanding to draw curves of new course distances by ship's heading test and utilize them at sea.

• 한국정밀공학회지
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• 제27권4호
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• pp.27-32
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• 2010

This paper presents an investigation into the pinhead forming process with the objective of finding the optimal forming conditions. In order to this, the orbital forming analysis of a heading MIG was carried out using the explicit finite element method. Relationships between temperature by forming of load and stresses, rake angle by forming final shape and stress distribution were investigated through analysises in order to find an efficient solution. As a result, the higher temperature and orbital rake angle were the better forming conditions.

• 한국항해항만학회지
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• 제37권4호
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• pp.329-335
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• 2013

This paper is to develop the position error equations including the attitude errors, the errors of nadir and ship's heading, and the errors of ship's position in the free-gyro positioning and directional system. In doing so, the determination of ship's position by two free gyro vectors was discussed and the algorithmic design of the free-gyro positioning and directional system was introduced briefly. Next, the errors of transformation matrices of the gyro and body frames, i.e. attitude errors, were examined and the attitude equations were also derived. The perturbations of the errors of the nadir angle including ship's heading were investigated in each stage from the sensor of rate of motion of the spin axis to the nadir angle obtained. Finally, the perturbation error equations of ship's position used the nadir angles were derived in the form of a linear error model and the concept of FDOP was also suggested by using covariance of position error.

• 수산해양기술연구
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• 제30권1호
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• pp.53-63
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• 1994

1) 강소성 유한 요소법 프로그램 RDHPSC는 2단헤딩 가공에 있어서의 신뢰 할 수 있는 해석수단이다. 2) RDHPSC에 의한 2단헤딩의 해석은 2단헤딩가공에서의 최적 가공 조건의 결정에 유용한 정보를 제공할 수 있다. 3) 2단헤딩 가공중의 금속흐름을 수치해석에서의 격자 변형에 의해 관찰될 수 있다. 4) 2단헤딩 가공중의 표면 결함의 발생가능성은 수치해석 결과에서 원수방향응력과 계수 D를 관찰함으로서 탐색되어질 수 있다. 5) 2단헤딩가공중에 있어서의 내부결함 발생가능성은 수치해석의 격차 변형을 통하여 알 수 있다. 6) 마무리 가공금형 수명에 대한 최적가공조건은 수치해석에서의 접촉압력을 조사하여 얻을 수 있다.(이 논문의 결론부분임)

• 한국해양공학회지
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• 제34권2호
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• pp.77-88
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• 2020

In this study, heading characteristics and heading control performances were evaluated to achieve the wave shield effect. The wave shield effect originating from heading control reduces the relative motions of moored vessels in a floating liquefied natural gas bunkering terminal (FLBT). Therefore, loading and off-loading performances are improved through reduced relative motion. For the objective of this study and efficiency of the analysis, a simplified model was used that assuming no relative motion of the moored vessels in the FLBT. The simplified model involved modeling the environmental loads and inertia of several floating bodies, including FLBT, into the environmental loads and inertia of a single vessel. The simplified model was validated through comparisons with model tests. With the simplified model, heading characteristics and heading control simulations were performed using low-frequency planar motion equations. The heading characteristics and heading control performances of FLBT were analyzed through the results of simulations under the expected environmental conditions. The capacity of the tunnel thrust for the heading control performance was confirmed to be adequate for improvement of the loading and off-loading performances using the wave shielding effects under the operation conditions.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.32-32
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• 2017

To increase rice production, manipulating plant architecture, especially developing new high-yielding cultivars with erect leaves, is crucial in rice breeding programs. Leaf inclination angle determines the light extinction coefficient (k) of the canopy. Erect leaves increase light penetration into the canopy and enable dense plantings with a high leaf area index, thus increasing biomass production and grain yield. Because of erect leaves, the high-yielding indica rice cultivar 'Takanari' has smaller k during ripening than 'Koshihikari', a japonica cultivar with good eating quality. In our previous study, using chromosome segment substitution lines (CSSLs) derived from a cross between 'Takanari' and 'Koshihikari', we detected seven quantitative trait loci (QTLs) for leaf inclination angle on chromosomes 1 (two QTLs), 2, 3, 4, 7, and 12. In this study, we developed a near-isogenic line (NIL-3) carrying a 'Takanari' allele for increased leaf inclination angle on chromosome 3 in the 'Koshihikari' genetic background. We compared k, dry matter production, and grain yield of NIL-3 with those of 'Koshihikari' in the field from 2013 to 2016. NIL-3 had higher inclination angles of the flag, second, and third leaves at full heading and 3 (- 4) weeks after full heading and smaller k of the canopy at the ripening stage. Biomass at full heading and leaf area index at full heading and at harvest did not significantly differ between NIL-3 and 'Koshihikari'. However, biomass at harvest was significantly greater in NIL-3 than in 'Koshihikari' due to a higher net assimilation rate at the ripening stage. The photosynthetic rates of the flag and third leaves did not differ between NIL-3 and Koshihikari at ripening. Grain yield was higher in NIL-3 than 'Koshihikari'. Higher panicle number per square meter in NIL-3 contributed to the higher grain yield of NIL-3. We conclude that the QTL on chromosome 3 increases dry matter and grain production in rice by increasing leaf inclination angle.

• 자동차안전학회지
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• 제8권1호
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• pp.13-18
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• 2016

More than 80 percent of traffic accidents related with lane departure believed to be the result of crossing the lane due to either negligence or drowsiness of the driver. Lane-departure related accident in the highway usually involve high fatality. Even though LDWS is believed to prevent accident 25% and reduce fatalities by 15% respectively, its effectiveness in performance is yet to be confirmed in many aspects. In this study, the vehicle lateral locations relative to warning zone envelop (earliest and latest warning zone) defined in ISO standard, ECE and NHTSA regulations are compared with respect to various factors including delays, vehicle speed and vehicle heading angle with respect to the lane. Since LDWS is designed to be activated at the speed over 60 km/h, vehicle speed range for the study is set to be from 60 to 100 km/h. The vehicle heading angle (yaw angle) is set to be up to 5 degree away from the lane (abrupt lane change) considering standard for lane change test using double lane-change test specification. The TLC is calculated using factors like vehicle speed, yaw angle and reaction time. In addition, the effect of vehicle type and reaction time have been considered to assess LDWS safety.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.463-467
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• 2005

In this paper, the guidance law applicable to formation flight of UAV in three-dimensional space is proposed. The concept of miss distance, which is commonly used in the missile guidance laws, and Lyapunov stability theorem are effectively combined to obtain the guidance commands of the wingmen. The propose guidance law is easily integrated into the existing flight control system because the guidance commands are given in terms of velocity, flight path angle and heading angle to form the prescribed formation. In this guidance law, communication is required between the leader and the wingmen to achieve autonomous formation. The wingmen are only required the current position and velocity information of the leader vehicle. The performance of the proposed guidance law is evaluated using the complete nonlinear 6-DOF aircraft system. This system is integrated with nonlinear aerodynamic and engine characteristics, actuator servo limitations for control surfaces, various stability and control augmentation system, and autopilots. From the nonlinear simulation results, the new guidance law for formation flight shows that the vehicles involved in formation flight are perfectly formed the prescribed formation satisfying the several constraints such as final velocity, flight path angle, and heading angle.

• 제어로봇시스템학회논문지
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• 제19권10호
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• pp.936-940
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• 2013

As the ageing population grows around the world, the demand for electric wheelchairs, an important mobility assistance device for the disabled and elderly, is gradually increasing. Therefore, a number of studies related to intelligent wheelchairs are actively underway to improve safety and comfort for wheelchair users. However, previous collision avoidance studies for intelligent wheelchairs have concentrated on collision avoidance methods with the shortest distance and by only changing either velocity or heading angle, rather than considering the forces exerted on the user. If a collision avoidance algorithm that does not consider these forces is applied to an intelligent wheelchair, there is a possibility of an accident due to falling as wheelchair users are generally disabled and elderly people. In this paper, we propose a collision avoidance algorithm which minimizes the forces exerted on a wheelchair user by minimizing the variation of the wheelchair's velocity and heading angle when the sizes, positions, velocities, and heading angles of a wheelchair and a moving obstacle are known.