• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.285-289
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• 2004

An optimal interplanetary trajectory is presented for Human Outer Planet Exploration (HOPE) by using an advanced magnetoplasma spacecraft. A detailed optimization approach is formulated to utilize Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine with capabilities of variable specific impulse, variable engine efficiency, and engine on-off control. To design a round-trip trajectory for the mission, the characteristics of the spacecraft and its trajectories are analyzed. It is mainly illustrated that 30 MW powered spacecraft can make the mission possible in five-year round trip constraint around year 2045. The trajectories obtained in this study can be used for formulating an overall concept for the mission.

• 대한기계학회논문집A
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• 제28권5호
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• pp.495-502
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• 2004

In this paper, kinematic structure of parallel manipulator having 6-DOF is determined to follow the specific trajectory represented by several curves expressed by the parametric variable functions. In addition, the parallel manipulator is designed to have a high dexterity by considering a kinematic isotropy which can stabilize the motion of the moving platform in the restricted workspace.

• 대한기계학회논문집A
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• 제33권8호
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• pp.779-785
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• 2009

This paper is concerned with a computational approach for topology optimization of geometrically nonlinear structures following specific load-displacement trajectories. In our previous works, attention was paid to stabilize topology optimization involving large displacement and a method called the element connectivity parameterization was developed. Here, we aimed to extend the element connectivity parameterization method to find an optimal geometrically nonlinear structure yielding a specific load-displacement trajectory. In contrast to designing a stiffest structure, the trajectory design problem requires special consideration in topology optimization formulation and solution procedure. Some numerical problems were considered to test the developed element connectivity parameterization based formulation.

• Journal of Computing Science and Engineering
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• 제5권4호
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• pp.346-353
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• 2011

With the advent of ubiquitous computing, a massive amount of trajectory data has been published and shared in many websites. This type of computing also provides motivation for online mining of trajectory data, to fit user-specific preferences or context (e.g., time of the day). While many trajectory clustering algorithms have been proposed, they have typically focused on offline mining and do not consider the restrictions of the underlying road network and selection conditions representing user contexts. In clear contrast, we study an efficient clustering algorithm for Boolean + Clustering queries using a pre-materialized and summarized data structure. Our experimental results demonstrate the efficiency and effectiveness of our proposed method using real-life trajectory data.

• International Journal of Control, Automation, and Systems
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• 제4권1호
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• pp.10-16
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• 2006

In this paper, moving a fragile object from an initial point to a specific location in the minimum time without damage is studied. In order to achieve this goal, initially, the maximum acceleration and velocity ranges are specified. These ranges can be dynamically generate on the planned path by the manipulator. The path can be altered by considering the geometrical constraints. Later, considering the impulsive force constraint on the object, the range of maximum acceleration and velocity are obtained to preserve object safety while the manipulator is carrying it along the curved path. Finally, a time-optimal trajectory is planned within the maximum allowable range of acceleration and velocity. This time-optimal trajectory planning can be applied to real applications and is suitable for both continuous and discrete paths.

• 제어로봇시스템학회논문지
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• 제22권3호
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• pp.233-240
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• 2016

This paper describes a three-dimensional reference trajectory generation method for giving commands to an unmanned air vehicle (UAV). The trajectory is a set of consecutive curves with constant acceleration during each interval and passing through via-points at specified times or speeds. The functional inputs are three-dimensional positions and times (or speeds) at via-points, and velocities at both boundaries. Its output is the time series of position values satisfying the piecewise constant acceleration condition. To be specific, the shape of the trajectory, known as the path, is first represented by splines using third degree polynomials. A numeric algorithm is then suggested, which can overcome the demerits of cubic spline method and promptly generate a piecewise constant acceleration trajectory from the given path. To show the effectiveness of the present scheme, trajectory generation cases were treated, and their speed calculation errors were evaluated.

• Transactions on Control, Automation and Systems Engineering
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• 제4권2호
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• pp.130-139
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• 2002

In this paper, at first, we investigate existing algorithms for finding the minimum infinity-norm solution of consistent linear equations and then propose a new algorithm. The proposed algorithm is intended to includes the advantages of computational efficiency as well as geometric explicitness. As a practical application example, optimum trajectory planning for redundant robot manipulators is considered. Also, an efficient approach avoiding discontinuity in trajectory is proposed by resolving the non-uniqueness problem of minimum infinity-norm solution. To be specific, the proposed method for checking possible discontinuity does not need any other algorithms in checking the possibility of discontinuity while previous work needs specially designed checking courses. To show the usefulness of the proposed techniques, an example calculating minimum infinity-norm solution for comparing the computational efficiency as well as the trajectory planning for a redundant robot manipulator are included.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.244-248
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• 1996

Nowadays, most shop floors using industrial robots have many problems such as constructing robot workcell, generating robot arm moving trajectory, etc.. In the case of programming robot-arms for a specific task, shop operator commonly use the teach pendant to record the target position and determine the moving trajectory. However, such a teaching process may result in an inefficient trajectory in the sense of moving distance and joint angle fluctuation. Moreover, shop operators who have little knowledge about robot programming process need a lot of learning time and cost. The purpose of this paper is to propose a user friendly robot programming method to program robot-arms easily and efficiently for shop operator so that the programming time is reduced and a short and stable trajectory is obtained.

• 대한수학회논문집
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• 제34권1호
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• pp.333-349
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• 2019

The paper study the curvature theory of a line-trajectory of constant Disteli-axis, according to the invariants of the axodes of moving body in spatial motion. A necessary and sufficient condition for a line-trajectory to be a constant Disteli-axis is derived. From which new proofs of the Disteli's formulae and concise explicit expressions of the inflection line congruence are directly obtained. The obtained explicit equations degenerate into a quadratic form, which can easily give a clear insight into the geometric properties of a line-trajectory of constant Disteli-axis with the theory of line congruence. The degenerated cases of the Burmester lines are discussed according to dual points having specific trajectories.

• 한국정보과학회논문지:데이타베이스
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• 제31권2호
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• pp.150-162
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• 2004

이동체는 시간에 따라 위치를 변경하는 특성과 이동체의 경로는 궤적으로 표현되는 특성을 가진다. 이동체 궤적 데이타에 대한 저장 및 검색을 처리하는 이동체 데이타베이스 시스템에서는 효율적인 데이타 접근 방법이 필요하다. 특히 궤적 검색을 위한 대표적인 질의 유형인 복합 질의는 영역내의 궤적 검색과 궤적의 일부분을 추출하는 과정을 포함한다. 그러나, 영역 질의에 우수한 색인 방법은 부분 궤적을 추출하기 위한 비용이 높은 단점을 가진다. 반면, 궤적 질의를 위한 색인 방법의 경우 노드간의 중첩이 매우 높아 영역내의 궤적 검색 비용이 높은 단점이 있다. 이 논문에서는 이동체 데이타베이스에서 복합 질의를 효율적으로 처리하기 위해 TR-tree를 제시한다. TR-tree는 궤적 질의를 위해 궤적 보존 및 단말 노드의 용량을 증가시키고, 영역 질의 처리를 위해 사장영역과 MBB(Minimum Bounding Box)의 중첩을 감소시키는 논리적 궤적 분할을 지원하는 특징을 가진다. 실험 평가에서 TR-tree는 STR-tree, TB-tree의 복합 질의 성능 비교에서 평균 25%의 노드 접근 회수를 감소시킨다.