• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.921-925
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• 1987

This paper presents the recent findings for collision avoidance of two manipulators in addition to the results shown in Lee [4]. The collision situation we assume here is that the prespecified final time $K_{f}$ and the prespecified path of one robot can be modified for the purpose of collision avoidance with the other robot. The collision avoidance problem is resolved into three independent categories for a systematic approach.h.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.541-551
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• 2020

Based on the trend, there have been numerous researches analysing the ship collision risk. However, in this scope, the navigational conditions and external environment are ignored or incompletely considered in training or/and real situation. It has been identified as a significant limitation in the navigational collision risk assessment. Therefore, a novel algorithm of the ship navigational collision risk solving system has been proposed based on basic collision risk and vulnerabilities of marine accidents. The vulnerability can increase the possibility of marine collision accidents. The factors of vulnerabilities including bad weather, tidal currents, accidents prone area, traffic congestion, operator fatigue and fishing boat operating area are involved in the fuzzy reasoning engines to evaluate the navigational conditions and environment. Fuzzy logic is employed to reason basic collision risk using Distance to Closest Point of Approach (DCPA) and Time of Closest Point of Approach (TCPA) and the degree of vulnerability in the specific coastal waterways. Analytical Hierarchy Process (AHP) method is used to obtain the integration of vulnerabilities. In this paper, vulnerability factors have been proposed to improve the collision risk assessment especially for non-SOLAS ships such as coastal operating ships and fishing vessels in practice. Simulation is implemented to validate the practicability of the designed navigational collision risk solving system.

• 한국정보과학회논문지:시스템및이론
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• 제31권3_4호
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• pp.247-256
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• 2004

본 논문에서는 애니메이션 속도에 무관한 충돌 탐지 알고리즘을 제안한다. 현재까지 개발된 대부분의 충들 탐지 알고리즘들은 점진적(incremental) 알고리즘들로서, 현 시점에서의 가까운 점(근점)을 찾기 위하여 이전 시점의 근점 주위를 먼저 찾는다. 그런데 만일 움직이는 물체가 충돌 반응에 의해서 큰 토크를 받게 된다면 회전 속도가 증가하게 되어, 다음 시점에서의 실제 근점은 현 시점에서의 근점과는 매우 동떨어져 있어 엉뚱한 위치에서 근점을 찾게 되는 단점을 가진다. 그러므로, 최악의 경우에는 각 시점에서 $O(n^2)$, 시간이 소요될 수 있다. 또한 애니메이션 속도에 따라 이러한 점진적 계산 회수가 변하게 되어 전체적인 알고리즘의 소요 시간이 변하게 되는 단점을 가지고 있다. 본 논문에서는 이러한 문제점을 근본적으로 해결하고자 새로운 방법을 제안하고자 한다. 먼저, 기하학 특성을 내포하는 구면 근점 다이아그램을 생성하고, 이를 이용하여 두 물체간의 단일 거리 함수를 생성한다. 충돌 시점을 효율적으로 찾기 위해서 구간 뉴튼 방법을 거리함수에 적용한다.

• 산업공학
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• 제22권3호
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• pp.278-286
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• 2009

The anti-collision algorithms to identify a number of tags in real-time in RFID systems are divided into the anti-collision algorithms based on the Framed slotted ALOHA that randomly select multiple slots to identify the tags, and the anti-collision algorithms based on the Tree-based algorithm that repeat the questions and answer process to identify the tags. In the hybrid algorithm which is combined the advantages of these algorithms, tags are distributed over the frames by selecting one frame among them and then identified by using the Query tree frame by frame. In this hybrid algorithm, however, the time of identifying all tags may increase if many tags are concentrated in a few frames. In this study, to improve the performance of the hybrid algorithm, we suggest an improved algorithm that the tags select a specific group of frames based on the earlier bits of the tag ID so that the tags are distribute equally over the frames. By using the simulation and mathematical analysis, we show that the suggested algorithm outperforms traditional hybrid algorithm from the viewpoint of the number of queries per frame and the time of identifying all tags.

• 한국통신학회논문지
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• 제28권6B호
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• pp.544-552
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• 2003

본 논문에서는 단일 채널에서 동작하는 무선인식 시스템에서 다수의 트랜스폰더가 접근할 때 데이터 충돌을 방지 할 수 있는 명령 코드 충족 알고리즘을 제안하였다. 기존에 사용되고 있는 시간 영역 방법에서는 무조건 충돌을 발생시키지만, 명령 코드 충족 알고리즘은 명령 코드를 충족해야만 데이터를 송신할 수 있게 구현함으로써 데이터 충돌을 방지하였다. 만약 트랜스폰더에서 데이터를 송신하는 중 또 다른 트랜스폰더가 데이터를 송신한다 면 인식거리의 차이에 의해서 데이터 도착속도가 틀려짐을 이용하여 원하는 데이터만 수신할 수 있게 하였다. 제안된 명령 코드 충족 알고리즘을 적용하기 위하여 13.56MHz대역의 무선인식 시스템을 제작하여 1비트 데이터 전송 시간인 14$\mu\textrm{s}$ 차이를 확보함으로써 데이터 충돌 방지하고 그로인한 데이터 손실이 방지됨을 실험을 통하여 입증하였다.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2006년도 추계공동학술대회
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• pp.239-254
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• 2006

In mold structure machining, tool interference is a phenomenon which results from a collision between a blade of tool and a workpiece. Also tool collision is a phenomenon which results from a collision of holder with the object to be machined. These phenomena not only cause damages to mold and tool but also increase machining time and cost. To detect a collision of a tool to mold structure, first of all, the mold structure and a tool must be defined with famous geometric models such CSG, B-rep, and Voxel. A tool is defined as a combination of the blade, the shank, and the holder. This thesis reviews various collision detection algorithms using z-map and computer 3D graphic collision detection algorithms for the tool in machining a mold structure.

• 제어로봇시스템학회논문지
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• 제16권3호
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• pp.233-238
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• 2010

This paper describes a multi-mobile robot system with fuzzy rule based structure in collision avoidance. Collision avoidance is an important function to perform a given task collaboratively and cooperatively in multi-mobile robot environments. So the important but challenging problem is handled in this paper. Considered obstacles for collision avoidance between multi mobile robots are static, dynamic, or both of them at the same time. Using the fuzzy rule based structure, distance and angle from a robot to obstacles are described as fuzzy linguistic values and steering angle for the robot are updated from the collision environments. As a result, the multi-mobile robot can modify a global path from a robot itself to its own target. In addition, avoiding collision with static or dynamic obstacles for the robot system can be achieved. Simulation based experimental results are given to show usefulness of this method.

• 한국통신학회논문지
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• 제33권10A호
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• pp.987-996
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• 2008

본 논문에서는 기존 리더 충돌방지 알고리즘인 Channel Monitoring 알고리즘, Pulse Protocol 알고리즘에 대하여 살펴보고, 태그인식시간을 감소시키고, 데이터 처리량, 시스템 효율을 증가 시킬 수 있는 슬롯 점유확률을 이용한 Pulse Protocol 기반의 Hybrid 리더 충돌 방지 알고리즘을 제안한다. 제안하는 알고리즘은 Pulse Protocol 알고리즘의 성능을 향상시키기 위하여 Channel Monitoring 알고리즘에서 사용되고 있는 슬롯의 점유확률 (Occupied Probability)을 이용한다. 즉, 리더들은 랜덤 backoff 시간을 생성한 후, 자신이 사용하게 될 슬롯의 점유확률을 확인하고, 이 슬롯의 점유확률이 0보다 크다면, 새로운 랜덤 backoff 시간을 생성하여 리더간의 충돌을 피한다. 기존 알고리즘들과 제안하는 알고리즘과의 성능을 태그인식시간, 데이터 처리량 및 시스템 효율 등의 성능분석항목들을 통하여 비교 및 분석하여, 제안하는 알고리즘에 의하여 리더의 개수가 증가함에 따라 7% 정도의 태그인식시간 및 데이터 처리량 성능 향상을 확인한다.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.233-247
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• 1999

Traffic accidents are normally caused by late or faulty judgements due to the driver's inaccurate estimation of the distance, velocity, and acceleration from the surrounding vehicles as well as his carelessness or inattention. Thus, the development of collision avoidance systems is motivated by their great potential for increased vehicle safety. A typical collision avoidance system consists of the forward-looking sensor, the criteria for activation of collision warming and avoidance, the collision avoidance maneuvers, and the user interface. This thesis is concerned with the development of a collision warning algorithm in which the driver is warned of approaching collision with the visual and/or the audible signals . The warning algorithm based on fuzzy logic is presented here based on new warning criteria. It has been newly derived from the conventional warning equation by adding a new input variable of the required deceleration to avoid collision. The algorithm is also able to adapt to the individual driver's taste along with the different road conditions by externally controlling the warning intensity. Finally , the proposed algorithm has been validated using computer simulation.

• Journal of Information Processing Systems
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• 제16권6호
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• pp.1324-1342
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• 2020

Various modified algorithms of rapidly-exploring random tree (RRT) have been previously proposed. However, compared to the RRT algorithm for collision avoidance with global and static obstacles, it is not easy to find a collision avoidance and local path re-planning algorithm for dynamic obstacles based on the RRT algorithm. In this study, we propose boundary-RRT*, a novel-algorithm that can be applied to aerial vehicles for collision avoidance and path re-planning in a three-dimensional environment. The algorithm not only bounds the configuration space, but it also includes an implicit bias for the bounded configuration space. Therefore, it can create a path with a natural curvature without defining a bias function. Furthermore, the exploring space is reduced to a half-torus by combining it with simple right-of-way rules. When defining the distance as a cost, the proposed algorithm through numerical analysis shows that the standard deviation (σ) approaches 0 as the number of samples per unit time increases and the length of epsilon ε (maximum length of an edge in the tree) decreases. This means that a stable waypoint list can be generated using the proposed algorithm. Therefore, by increasing real-time performance through simple calculation and the boundary of the configuration space, the algorithm proved to be suitable for collision avoidance of aerial vehicles and replanning of local paths.