• 제어로봇시스템학회논문지
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• 제22권3호
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• pp.217-225
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• 2016

In this paper, we propose an improved path planning method and obstacle avoidance algorithm for two-wheel mobile robots, which can be effectively applied in an environment where obstacles can be represented by circles. Firstly, we briefly introduce the rapidly exploring random tree (RRT) and single polar polynomial (SPP) algorithm. Secondly, we present additional two methods for applying our proposed method. Thirdly, we propose a global path planning, smoothing and obstacle avoidance method that combines the RRT and SPP algorithms. Finally, we present a simulation using our proposed method and check the feasibility. This shows that proposed method is better than existing methods in terms of the optimality of the trajectory and the satisfaction of the kinematic constraints.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1939-1944
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• 2003

This paper presents a global path planning algorithm based on a visibility graph method, and applies additionally various constraints for constructing the reduced visibility graph. The modification algorithm for generating the rounded path is applied to the globally shortest path of the visibility graph using the robot size constraint in order to avoid the obstacle. In order to check the visibility in given 3D map data, 3D CAD data with VRML format is projected to the 2D plane of the mobile robot, and the projected map is converted into an image for easy map analysis. The image processing are applied to this grid map for extracting the obstacles and the free space. Generally, the tree size of visibility graph is proportional to the factorial of the number of the corner points. In order to reduce the tree size and search the shortest path efficiently, the various constraints are proposed. After short paths that crosses the corner points of obstacles lists up, the shortest path among these paths is selected and it is modified to the combination of the line path and the arc path for the mobile robot to avoid the obstacles and follow the rounded path in the environment. The proposed path planning algorithm is applied to the mobile robot LCAR-III.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1544-1549
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• 2004

A new collision avoidance algorithm is presented for two mobile robots in narrow corridor environments. When two robots meet each other in a narrow corridor, one should yield the way to the other robot. To solve the problem arising in this situation, they exchange their path to get information about crossing-points to check avoidance conditions, which are necessary for choosing the robot to yield. The conditions are summarized as follows. 1) If one robot blocks the path to the closest crossing-point in front of the other robot. 2) If the closest crossing-point of each robot is the same point. 3) Which robot is closer to the closest crossing-point. In this paper, we propose a path planning algorithm for the robot which yield the way. Simulation results are presented to verify the feasibility of the proposed collision avoidance algorithm.

• 산업기술연구
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• 제21권A호
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• pp.231-240
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• 2001

U-turn and P-turn as well as left-turn restriction exist in real traffic network. the optimal route should be selected for considering these using shortest path algorithms. But, the traditional algorithms have some limitations to use for considering there. The objective of this paper is to modify Dijkstra algorithm in order to find the optimal path in real traffic network. The continuous three nodes are used to check turn-restrictions and exclude these from and optimal path. A virtual connection is used to consider U-turn and P-turn.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1128-1131
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• 1996

The collision-free path planning presented here uses linear parametric curve with one intermediate connection point between start and target points. The algorithm, in which connection point is organized in elliptic chord.(.theta., .delta.), maps objects in Euclidean Space into images in CPS through intersection check between path and obstacles a process defined as GM. Elliptic locus has special property that the total distance between focus points through a point on ellipse is the same regardless of .theta.. Hence by locating the start and target points to focus points of ellipse, and organizing connection point in elliptic coordinate, the .delta.-axis of CPS represents length of path. The GM of EWS requires calculation of interference in circumferential direction only. The procedures for GM is developed which include categorization of obstacles to reduce calculation amount. Simulations of GM of EWS, on a PC with Pentium/90MHz, is carried out to measure performance of algorithm and the results are reported on a table. The simulations are done for number of cases with different number of obstacles and location of start/target points.

• 제어로봇시스템학회논문지
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• 제20권12호
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• pp.1272-1277
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• 2014

This article describes a path planning algorithm for fixed-wing UAVs when a real terrain should be considered. Nowadays, many UAVs are required to perform mission flights near given terrain for surveillance, reconnaissance, and infiltration, as well as flight altitude of many UAVs are relatively lower than typical manned aerial vehicles. Therefore, real terrain should be considered in path planning algorithms of fixed-wing UAVs. In this research, we have extended a spline-$RRT^*$ algorithm to three-dimensional planner. The spline-$RRT^*$ algorithm is a $RRT^*$ based algorithm, and it takes spline method to extend the tree structure over the workspace to generate smooth paths without any post-processing. Direction continuity of the resulting path is guaranteed via this spline technique, and it is essential factor for the paths of fixed-wing UAVs. The proposed algorithm confirm collision check during the tree structure extension, so that generated path is both geometrically and dynamically feasible in addition to direction continuity. To decrease degrees of freedom of a random configuration, we designed a function assigning directions to nodes of the graph. As a result, it increases the execution speed of the algorithm efficiently. In order to investigate the performance of the proposed planning algorithm, several simulations are performed under real terrain environment. Simulation results show that this proposed algorithm can be utilized effectively to path planning applications considering real terrain.

• 한국통신학회논문지
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• 제38B권2호
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• pp.146-153
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• 2013

IR-UWB 레이더는 송신안테나에서 UWB 대역을 갖는 임펄스를 방사하고 목표물에 부딪혀 수신안테나에 도달하는 지연시간, 즉 Time of Arrival(TOA)를 통해 목표물의 거리를 추정한다. 본 논문에서는 기존의 거리추정 알고리즘을 보완하여 실내 환경에서 더욱 정확한 거리 추정이 가능하게 하는 알고리즘을 제안한다. Novelda(사(社))의 NVA6000 UWB Transceiver를 장착한 IR-UWB Radar모듈을 사용하여 수신신호 데이터들을 취합하였다. 수신신호 데이터를 통해 얻은 Adjusted TOA(ATOA)를 히스토그램으로 나타내어 다중경로의 경향을 알아보고 그 결과 ATOA값들은 감마 분포의 특성을 갖는다는 점을 실험적으로 확인하였다. 이 감마 분포 특성을 이용하여 새로운 알고리즘을 제안하며, 기존의 알고리즘과의 성능비교를 수행하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.79-80
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• 2007

This paper deals with generating multi-ped mobile robot's optimal path and its simulation. The multi-ped robot has six-legs which make it possible to move actively by attached driving wheel at the end of legs. The simulation environment is created similarly to the indoor environment as simple obstacles and walls. Also simulator can reconstruct an simulation environment. In this paper, the suggested simulator can generate the optimal path from starting point to destination by applying the A* algorithm and Bug2 algorithm. Then it is possible to check algorithms as 3D screen and we can simulate under the generated path.

• 한국항공우주학회지
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• 제50권3호
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• pp.157-164
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• 2022

본 논문에서는 무인기의 경로 계획을 위한 산악 지형, 레이더 그리고 방공망 등을 3차원 환경으로 구현하고, Sampling 기반의 경로 계획 알고리즘인 PRM 알고리즘을 사용하여 경로 계획 및 재계획을 수행하는 방안에 대해 서술한다. 기존의 PRM 알고리즘의 경우 생성된 노드 사이에 장애물 존재 여부를 확인하기 위한 계산이 노드 간 1:1로 이루어지고 연속적으로 수행되어 노드 수나 노드를 연결하는 거리에 계산량이 크게 영향을 받는다. 이러한 부분을 개선하기 위해 제안하는 LineGridMask 기법을 통해 장애물 존재 여부 확인 방식을 단순화하고, 병렬화를 통해 경로 계획의 계산 시간을 감소시킨다. 마지막으로 기존 PRM 알고리즘과의 성능을 비교한 결과, 경로 계획에서는 최대 88%, 재계획의 경우 최대 94%까지 계산 시간이 감소하였음을 확인하였다.

• 한국컴퓨터정보학회논문지
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• 제8권4호
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• pp.47-56
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• 2003

이동 단말기와 이동 통신망이 급격하게 발전함에 따라 멀티미디어 자료를 재생하는 환경에서 종단간 서비스 품질이 다른 경우들이 발생하고 있다. 따라서 주어진 트랜스코더와 통신망을 고려하여 근원지 데이터를 목적지에서 요구하는 재생 서비스 품질에 맞게 변환하여 재생하기 위한 트랜스코딩 경로를 생성하는 알고리즘이 연구되었다. 그러나 이 방법은 멀티미디어 스트림이 트랜스코더에서 처리될 때 필요한 매개 변수인 워크로드와 처리량 중에서 워크로드만을 고려하였다. 그러므로 이 방법에 의하여 생성된 트랜스코딩 경로는 목적지에서 요구하는 서비스 품질에 맞게 재생 가능한지 검사하기 위하여 추가적인 계산을 필요로 한다. 이를 해결하기 위하여 본 논문은 멀티미디어 스트림이 목적지에 도착할 때 필요한 등시성 성질을 평가 함수에 이용한 T 알고리즘을 제안하였다. 즉, 여러 트랜스코딩 경로들 중에서 등시성 성질을 근거로 한 경험적 탐색으로 추적 재생 가능한 경로를 선택하는 방법이다. 제안된 알고리즘을 사용하면 종단간 상이한 서비스 품질로 실시간 전송되는 멀티미디어 데이터를 재생할 수 있는 트랜스코딩 경로를 좀 더 빠르게 생성할 수 있다.