• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.574-577
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• 2009

본 논문은 외판원 문제(TSP: Traveling Salesman Problem)를 이용하여 로봇중심의 FMC(Flexible Manufacturing Cell)에서 반송 로봇의 작업순서를 설계하는 방법을 제시하였다. 이를 위해, 먼저 다수의 설비와 반송 로봇으로 구성된 대표적인 로봇 중심의 FMC를 가상으로 설계한 후, 실험계획법을 이용하여 다양한 조건에서의 주요 반응변수들의 인과관계를 규명하였다. 실험결과, 처리량, 반송로봇의가동률, 그리고 Buffer의 평균 대기 작업물의 수가 주요 반응변수들로 선정되었으며, 이를 기반으로 순서기반 조합최적화 문제인 TSP로 로봇 작업순서를 설계하였다. 제안한 방법과 기존의 방법을 비교하기 위해서 시뮬레이션을 수행 한 결과 제안된 TSP 방법이 기존의 방법 보다 반송 로봇의 교착 (Deadlock) 상태를 방지하여 처리량 등 주요 반응변수들 모두를 향상 시키는 결과를 가져왔다. 더불어,이 방법은 본 연구에서 제시한 FMC 뿐 아니라 반도체나 LCD(Liquid Crystal Display) 생산 공정과 같이 반송 로봇에 의해 구성되어 있는 장치 산업분야에 적용가능하다는 측면에서 큰 효과가 기대된다.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2495-2497
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• 2003

본 논문에서는 다수의 AGV를 이용한 물류자동화 시뮬레이션에 대해 연구하였다. 각각의 AGV가 독립적으로 명령을 수행하도록 가상의 AGV를 제안하고 이미 연구된 AGV의 주행경로 표현방법, 경로망 구성방법을 이용하였다. 작업요구시 주어진 작업을 가장 빨리 수행 할 수 있는 AGV를 선정하고 최적 경로 계획을 수행하였다. 그리고 작업을 수행 중인 AGV는 경로 합류점에서의 교착상태(dead lock)와 충돌이 발생할 수 있는데 이를 방지하기 위한 통제구역을 정의하고 교통제어를 수행하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.387-392
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• 2006

In the environment where AGVs(Automated Guided Vehicles) operate concurrently in limited space, collisions. deadlocks, and livelocks which have negative effect on the productivity of AGVs occure more frequently. The accelerated motion of an AGV is also the factor that make the AGV routing more difficult because the accelerated motion makes it difficult to estimate the vehicle's exact travel time. In this study, we propose methods of avoiding collisions, deadlocks, and livelocks using OAR(Occupancy Area Reservation) table, and selecting best route by estimating the travel time of an AGV in accelerated motion. A time-driven simulation validated the effectiveness of the proposed methods.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.105-108
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• 2004

다단계 보안데이터베이스 시스템에서 기본적인 병행수행 제어 기법들은 비밀채널과 교착상태등과 같은 문제들이 발생하였다. 이에 직렬화 순서를 동적으로 재조정함으로서 해결하려는 방안이 있었지만, 알고리즘의 복잡성으로 인해 오버 헤드와 많은 수행시간이 필요하게 되었고, 이에 따라 많은 양의 시스템 자원과 높은 사양의 시스템을 요구하게 되었다. 또한 이러한 방법은 다중 버전을 사용함으로서 추가적인 관리비용이 높게 되었고, 각각의 트랜잭션이 지연 및 재수행이란 불필요한 과정을 반복하게 되었다. 따라서 본 논문에서는 제안한 알고리즘은 데이터베이스의 용도에 맞게 직렬화 순서를 보장하여 스케줄을 관리하는 요청 2단계 로킹기법(Request Two-phase Locking)으로서 이는 2단계 로킹기법의 기본원리에 요청로크를 사용함으로 보다 효율적으로 병행제어를 할 수 있다. 여기서 요청로크는 각각의 트랜잭션 스케줄에 로크획득 및 해제를 병행수행제어의 필요에 따라 유동적으로 할 수 있으며, 읽기로크, 쓰기로크, 요청로크라는 3가지 로킹모드를 통해 대처방안을 마련함으로서, 충돌을 방지하며, 충돌연산의 특성에 따라 직렬화 순서를 동적으로 조정함으로 블록킹을 막는 병행제어를 응용하여 병렬성을 유지한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.389-397
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• 2021

The control characteristics after the failure of the control moment gyros, the actuators for satellite attitude control, were analyzed. In particular, the situation where one out of four failed was considered. For the most commonly used pyramids and box-90 structures, the singularities and singular surfaces after failure were analyzed and compared. Dynamic equations for the process of reducing the wheel speed after the failure were derived. The process of stabilizing the angular velocity of a satellite while absorbing the momentum of the faulty module by the three normal modules was analyzed. For singular shapes, the remaining CMGs may be locked or excessively shake. The authors proposed that it can be prevented by rearranging the gimbal angles.

• Journal of Navigation and Port Research
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• v.30 no.10 s.116
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• pp.855-860
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• 2006

In the environment where multiple AGVs(Automated Guided Vehicles) operate concurrently in limited space, collisions, deadlocks, and livelocks which have negative effect on the productivity of AGVs occure more frequently. The accelerated motion of an AGV is also one of the factors that make the AGV routing more difficult because the accelerated motion makes it difficult to estimate the vehicle's exact travel time. In this study, we propose methods of avoiding collisions, deadlocks, and livelocks using OAR(Occupancy Area Reservation) table, and selecting best route by estimating the travel time of an AGV in accelerated motion. A set of time-driven simulation works validated the effectiveness of the proposed methods.

• Journal of Advanced Navigation Technology
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• v.23 no.1
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• pp.1-7
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• 2019

Thisstudy presentsthe development of a fast-time airport surface simulator. The simulator usesthe output from a first-come first-served (FCFS) scheduler and has adopted one-dimensional dynamic model to simulate the movement of the aircraft on the surface. Higher collision risks situations in the airport surface traffic are analyzed to classify those situations into six cases. A conflict detection and resolution algorithm is implemented to maintain separation distance and to prevent deadlock. The simulator was tested with a scenario at the Incheon International Airport that contains 72 aircraft. Without the conflict detection and resolution, various conflict situations are identified. When the conflict detection and resolution algorithm is managing the traffic, it is confirmed that the conflicts are removed at the price of additional delays. In the conflict resolution algorithm, three prioritization strategies are implemented, and delayed aircraft count and average additional delays are compared. Prioritization based on remaining time or distance showed smaller total additional delay compared to choosing minimum delay priority for each situation.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.41 no.4
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• pp.8-20
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• 2023

Although the landscape architectural facilities need to be repaired according to historical and authentic techniques, the repair criteria of the standard specification for repairing cultural heritages still remain at a theoretical level, and there are little research analyzing detailed techniques from specific cases. This study discussed the repair techniques based on historical facts, around terraced flower beds, ponds, waterways and pavement in the government-managed spaces in the Joseon Dynasty. It analyzed the materials and finish of stone wall elements, the structural reinforcement and backfill materials, and topsoil surface protection measures, and drew out stones for foundation reinforcement, plastering material for agglutination, and stone processing techniques for the terraced flower beds. It examined the materials and structures of the rock revetment, foundation reinforcement and waterproofing techniques and drew out the outstanding characteristics of the foundation work, the recycle of used elements and the management of water quality, for the ponds. It primarily investigated the materials, foundation reinforcement and waterproofing techniques and discovered the repair techniques such as cover stone finishing methods, foundation and backfill materials, and flow reduction methods, for the waterways. Finally, it provided actual cases of the foundation composition, auxiliary materials and tools, and the use of cyperaceae and highlighted the existence of professional craftsmen called Bangjeonjang(方磚匠), for the pavement. This study is expected to be a staring point for discovering the repair techniques for landscape architectural facilities and used as basic data for revising specifications in the future.