• 제어로봇시스템학회논문지
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• 제19권7호
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• pp.599-604
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• 2013

Path planning of mobile robots has a purpose to design an optimal path from an initial position to a target point. Minimum driving time, minimum driving distance and minimum driving error might be considered in choosing the optimal path and are correlated to each other. In this paper, an efficient driving trajectory is planned in a real situation where a mobile robot follows a moving object. Position and distance of the moving object are obtained using a web camera, and the rotation angular and linear velocities are estimated using Kalman filters to predict the trajectory of the moving object. Finally, the mobile robot follows the moving object using a single curvature trajectory by estimating the trajectory of the moving object. Using the estimation by Kalman filters and the single curvature in the trajectory planning, the total tracking distance and time saved amounts to about 7%. The effectiveness of the proposed algorithm has been verified through real tracking experiments.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권3호
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• pp.143-148
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• 2001

A lot of robot trajectory tracking methods are proposed to enhance the tracking error, but irregular tracking errors are always accompanied and very hard to reduce it. Up to now, these irregular tracking errors are reduced by introducing more complicated control algorithms. But, it is intuitively obvious to reduce only the big errors selectively in the irregular ones for the better performance instead of using more complicated control algorithms. By the characteristics of the robot, big tracking errors of the end-effector are generated mostly due to the fast moving of joint. So, in this paper, we introduce a new method which reduce the big tracking errors by clippings the joint velocity with the constraint of given path. Using this method, desired trajectory tracking is obtained within the far reduced error bound. Also, this method is successfully applied to generate the path-constrained error reducing trajectories for 2-axis SCARA type robot.

• 한국지능시스템학회논문지
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• 제24권1호
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• pp.52-57
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• 2014

본 논문은 두 바퀴 이동로봇의 주행에 있어서 주어진 경로를 물리적 제한을 만족하면서 주행하는 관절 공간 궤적 생성방법을 실시간 운영체제를 이용하여 구현함으로써 실시간 제어 방법에 대하여 연구하였다. 경로계획에서 이동로봇의 방향을 고려하기 위하여 베지어곡선을 이용하였으며, 컨볼루션 연산자를 이용하여 로봇의 두 바퀴의 속도의 제한을 만족시켰다. 관절 공간의 궤적 생성과 생성된 궤적에 대한 속도명령, 그리고 엔코더 값 감시 등 실시간 태스크를 주기적 태스크로 구현하였으며 동기화를 위하여 실시간 메커니즘인 이벤트 플래그를 이용하여 구현하였다. 실제 로봇에 실시간 태스크를 구현하여 속도명령의 실시간성과 이에 따른 이동로봇의 주행실험 결과를 이용하여 궤적 추종 성능을 비실시간 시스템과 분석하였다. 결과를 통하여 실시간 성을 요구하는 제어시스템에서 실시간 다중 태스크 시스템의 유용성을 검증하였다.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제3권9호
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• pp.369-374
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• 2014

무인 자율주행 차량에서의 경로 생성 기법은 차량이 자동적으로 안전하고 효율적인 경로를 생성하고 주행할 수 있도록 해 준다. 경로에는 크게 전역경로와 지역경로가 있다. 전역경로는 차량이 출발점으로부터 도착점까지 가기 위해 주행해야 하는 구간을, 지역경로는 전역경로에서 얻은 구간을 주행하기 위해서 차량이 실제로 주행해야 할 경로를 의미한다. 본 논문에서는 지역경로 생성을 위하여 효율성 높은 곡선 함수를 사용하는 기존연구에서 더 나아가 학습을 통해 경로를 생성하는 방법을 제안한다. 먼저 강화학습을 통해서 후보경로에 대한 예측 보상 값을 얻고 보상 값이 최고가 되는 경로를 찾는 작업을 한다. 또한 인공 신경망을 통해서는 생성된 경로에 최적화된 조향 명령을 주기 위해 조향 각을 학습하는 작업을 한다. 더 나아가 주행하는 경로에 장애물이 발견되더라도 이를 효율적으로 회피하는 최적의 경로를 학습 기법을 통해 만들어낸다. 본 논문에서 제안된 알고리즘의 우수성은 실제 주행 환경으로 모델링한 시뮬레이션 실험을 통해 검증되었다.

• 한국해양공학회지
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• 제28권6호
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• pp.560-565
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• 2014

In this study, the problem of trajectory optimization for underwater gliders considering depth constraints is discussed. Typically, underwater gliders are controlled to dive and climb in a saw-tooth pattern at constant gliding angles. This approach is effective and close to optimal for deep water applications. However, the optimal path deviates from the saw-tooth path in shallow water conditions. This study focuses on finding more efficient gliding paths that can minimize the traverse time in the horizontal plane when the water depth is limited. The trajectory optimization problem is formulated into a minimum time control problem with inequality path constraints and hydrodynamic drag effects. A numerical approach based on the pseudo-spectral method is adopted as a solution approach, and the simulation results are presented.

• 한국생산제조학회지
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• 제24권4호
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• pp.374-385
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• 2015

In this paper, effective and user friendly CAM software is presented that automatically generates any three dimensional complex toolpaths according to a CAD drawing. In advanced manufacturing, often it is essential to scan the sample following a complex trajectory which consists of short (few microns) and multidirectional moves. The reported CAM software offers constant velocity for all short trajectory elements and provides an efficient shift of tool path direction in sharp corners of a tool trajectory, which is vital for any laser, based precision machining. The software also provides fast modification of tool path, automatic and efficient sequencing of path elements in a complicated tool trajectory, location of reference point and automatic fixing of geometrical errors in imported drawing exchange files (DXF) or DWG format files.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1402-1407
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• 2004

Moving a fragile object from an initial point to a goal location in minimum time without damage is pursued in this paper. In order to achieve the goal, first of all, the range of maximum acceleration and velocity are specified, which the manipulator can generate dynamically on the path that is planned a priori considering the geometrical constraints. Later, considering the impulsive force constraint of the object, the range of maximum acceleration and velocity are going to be obtained to keep the object safe while the manipulator is carrying it along the curved path. Finally, a time-optimal trajectory is planned within the maximum allowable range of the acceleration and velocity. This time optimal trajectory planning can be applied for real applications and is suitable for not only a continuous path but also a discrete path.

• 제어로봇시스템학회논문지
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• 제14권12호
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• pp.1238-1243
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• 2008

This paper presents an HILS(Hardware in the Loop Simulations) based experimental study for the UAV's flight trajectory planning/generation algorithms and guidance/control laws. For the various mission that is loaded on each waypoint, proper trajectory planning and generation algorithms are applied to achieve best performances. Specially, the 'smoothing path' generation and the 'tangent orbit path' guidance laws are presented for the smooth path transitions and in-circle loitering mission, respectively. For the control laws that can minimize the effects of side wind, side slip angle($\beta$) feedback to the rudder scheme is implemented. Finally, being implemented on real hardwares, all the proposed algorithms are validated with integrations of hardware and software altogether via HILS.

• 제어로봇시스템학회논문지
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• 제12권2호
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• pp.145-153
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• 2006

An optimal capturing trajectory for a moving object is proposed in this paper based on the observation that a single-curvature path is more accurate than double-or triple-curvature paths. Moving distance, moving time, and trajectory error are major factors considered in deciding an optimal path for capturing the moving object. That is, the moving time and distance are minimized while the trajectory error is maintained as small as possible. The three major factors are compared for the single and the double curvature trajectories to show superiority of the single curvature trajectory. Based upon the single curvature trajectory, a kinematics model of a mobile robot is proposed to follow and capture the moving object, in this paper. A capturing scenario can be summarized as follows: 1. Motion of the moving object has been captured by a CCD camera., 2. Position of the moving object has been estimated using the image frames, and 3. The mobile robot tries to follow the moving object along the single curvature trajectory which matches positions and orientations of the moving object and the mobile robot at the final moment. Effectiveness of the single curvature trajectory modeling and capturing algorithm has been proved, through simulations and real experiments using a 2-DOF wheel-based mobile robot.

• 한국정밀공학회지
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• 제27권1호
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• pp.76-83
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• 2010

There have been many studies regarding development of autonomous excavation system which is helpful in construction sites where repetitive jobs are necessary. Unfortunately, bucket trajectory planning was excluded from the previous studies. Since, the best use of excavator is to dig efficiently; purpose of this research was set to determine an optimized bucket trajectory in order to get best digging performance. Among infinite ways of digging any given path, criterion for either optimal or efficient bucket moves is required to be established. One method is to adopt work know-how from experienced excavator operator; However the work pattern varies from every worker to worker and it is hard to be analyzed. Thus, other than the work pattern taken from experienced operator, we developed an efficiency model to solve this problem. This paper presents a method to derive a bucket trajectory from optimization theory with empirical CLUB soil model. Path is greatly influenced by physical constraints such as geometry, excavator dimension and excavator workspace. By minimizing a energy function under these constraints, an optimal bucket trajectory could be obtained.