• Journal of the Korea Society for Simulation
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• v.28 no.4
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• pp.11-20
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• 2019

This paper presents a HILS(Hardware-In-the-Loop Simulation) approach for the verification of the OHT (Overhead Hoist Transport) controller in a semiconductor FAB. Since hundreds of OHTs can run simultaneously on the OHT network of a FAB, the full verification of the OHT controller is very essential to guarantee the stableness of the material handling system. The controller needs to fully consider not only normal situations but also abnormal situations that are difficult to predict. For the verification of the controller, we propose a HILS approach using a virtual environment including OHTs on a rail network, which can generate abnormal situations. The proposed HILS approach has been implemented and tested with various examples.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.406-412
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• 2006

In this paper, we propose OHT(optimized nough Transform) algorithm for the lane extraction. Input image is changed into 256 gray revel image. Gray level image is separated into background region and road region by using limited horizontal projection value. In separated road area, we apply OHT algorithm. OHT algorithm is characterized as follows. First, the number of candidate pixels is reduced using the outline orientation of the lane. Second, each range of the left and right lane is defined by limited ${\theta}$ Experimental results show that the proposed method is better than Hough Transform.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.7
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• pp.205-214
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• 2021

For smart manufacturing, most semiconductor sites utilize automated material handling systems(AMHS). As one of the AMHSs, the OHT control system(OCS) manages overhead hoist transports(OHT) that move along rails installed on the ceiling. This paper proposes a real-time scheduling system to efficiently allocate and control the OHTs in semiconductor logistics processes. The proposed system, as an independent subsystem within the OCS, is interconnected with the main subsystem of the OCS, so that it can be easily modified without the effect of other systems. To develop the system, we first identify the functional requirements of the semiconductor logistics process and classify several types of control scenarios of the OHTs. Next, based on SEMI(Semiconductor Equipment and Materials International) standard, we design sequence diagrams and interface messages between the subsystems. The developed system is interoperated with the OCS main subsystem and the database in real time and performs two major roles: 1) OHT dispatching and 2) pathfinding. Six integrated tests were carried out to verify the functions of the developed system. The system was normally operated on six basic scenarios and two exception scenarios and we proved that it is suitable for the mission planning of the OHTs.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.104.6-104
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• 2002

$\textbullet$ Contents 1 Introduction $\textbullet$ Contents 2 300mm OHT System $\textbullet$ Contents 3 function of OHT System $\textbullet$ Contents 4 Control Method $\textbullet$ Contents 5 Conclusion

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1085-1092
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• 2005

The OHT(Over Head Transportation) Vehicle transports heavy products quickly and repeatedly at the industrial workplace. The belt in the OHT vehicle is used to support the weight of the OHT Cage. The fatigue of the belt is caused by the dynamic load during the operation time. Since the fatigue fracture of the belt affects the safety at the workplace, the correct prediction of the dynamic load is necessary to calculate the fatigue life of the belt on the design step. In this paper a computer aided analysis method is proposed for the belt in the early design stage using dynamic analysis, stress analysis, belt tensile test, belt fatigue test and fatigue lift prediction method. From the dynamic load time histories and the stress of the belt FE model, a dynamic stress time history is produced. Using linear damage law and cycle counting method, fatigue life cycle is calculated. The method developed in this paper is used to reduce the time and cost for designing the OHT belt in different environment and condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.1005-1012
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• 2005

An OHT(Over Head Transportation) vehicle is an example of the industrial monorail vehicle, and it is used in the automobile, semiconductor, LCD manufacturing industries. OHT vehicle is moved by main wheels and guide rollers. The major function of the main wheel is to support and drive the OHT vehicle. The roles of the guide roller is the inhibition of derailment and steering of the OHT vehicle. Since the required vehicle velocity becomes faster and the required load capacity is increased, the durability characteristics of the wheel and roller, which was made of urethane, need to be increased. So it is necessary to estimate the fatigue life cycle of the wheel and roller. In this study, OHT dynamic model was developed by using the multi body dynamic analysis program ADAMS. Wheel and roller are modeled by the 3-D surface contact module. Especially, motor cycle tire mechanics is used in the wheel contact model. The OHT dynamic model can analyze the dynamic characteristic of the OHT vehicle with various driving conditions. And the result was verified by a vehicle traveling test. As a result of this study, the developed model is expected to predict wheel dynamic load time history and makes a contribution to design of a new monorail vehicle.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.05a
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• pp.368-371
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• 2020

반도체 제조시설의 효율성을 위해 대부분의 현장에서는 물류 자동화 시스템 (AMHS, Automated Material Handling System)을 도입하여 운영하고 있다. OHT(Overhead Hoist Transfer)는 반도체 공정에서 주로 활용되는 Monorail 컨베이어 형태의 자동 반송 시스템의 일종으로 작업물을 들고 제조라인 위에 설치된 레일을 따라 자율적으로 이동하는 방식으로 운영된다. 도체 물류 시스템의 계층적인 구조적 특징과 고가의 재료를 다루고, 외부유출이 어려운 실제 공정 현장, 실험 환경의 시간, 공간적 구축 등의 현실적 특징 때문에 반도체 제조 공정의 자동화 물류시스템에 대한 모델링 및 시뮬레이션을 통한 연구의 필요성이 대두되고 있다. 본 논문에서는 OHT를 효율적으로 제어하기 위해 DEVS(Discrete Event System Specifications) 형식론을 기반으로 OHT 시스템 모델링 및 시뮬레이션 설계 방법을 제안한다. 이를 위해 반도체 제조 시스템의 전반적인 물류 과정에 대해 분석하고, DEVS 형식론에 대해 연구하며, 이를 바탕으로 반도체 물류 시스템을 위한 모델링 및 시뮬레이션을 설계하였으면, 실험을 통해 제안된 모델리 반도체 물류 시스템 시뮬레이션을 수행할 수 있음을 보인다.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.7
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• pp.1159-1164
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• 2004

There is an Overhead Hoist Transport(OHT) for delivering the wafer in semiconductor processing. The transfer system is consists of carrier vehicle. rail, and support. OHTCMS(OHT Control and Management System) has to take the feature, such as the optimal control and integration with several OHT. In this paper, ESRA(Efficiency of Shortest - Route Algorithms) is proposed which can be transported optimal route and be prevented collision using the Floyd-Warshall algorithms. The proposed algorithm is verified through consecutive simulation for a long time.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1156-1163
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• 2006

본 논문은 Overhead Hoist Transport(OHT)를 운반 장비로 사용하는 반도체 생산 라인 자동물류시스템에서의 차량배차문제를 다룬다. 고려하는 반도체 라인은 18 개의 bay 와 6 개의 stoker 로 구성되며 160 대 이상의 OHT를 가진다. 자동물류시스템은 최소한의 OHT 대수로 하루 100,000 건의 웨이퍼를 이동시켜야 하며 반송시간과 편차를 최소화하여야 한다. 전통적인 차량배차규칙에서는 차량이 어떤 작업에 할당되면 그 관계가 변하지 않는 반면, 본 연구에서는 시스템 상황의 변화에 따라 차량을 작업에 재할당하는 방법을 제안한다. 시뮬레이션을 통해 제안된 방법을 shortest travel distance first 규칙과 비교한 결과, 필요한 OHT 대수, 반송시간과 반송시간의 편차 측면에서 획기적인 효용성 향상을 보였다.

• Composites Research
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• v.36 no.4
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• pp.259-263
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• 2023

This study investigated the open hole tensile (OHT) properties of carbon fiber/epoxy composites and compared them to bolt joint tensile (BJT) properties. The net nominal modulus and strength (1376 MPa) were found to be higher than the gross nominal strength (1041 MPa), likely due to increasing hole size. The OHT and BJT specimens exhibited similar stiffness, as expected without bolt rotation causing secondary bending. OHT specimens experienced a sharp drop in stress indicating unstable crack propagation, delamination, and catastrophic failure. BJT specimens failed through shear out on the bolt side and bearing failure on the nut side, involving fiber kinking, matrix splitting, and delamination, resulting in lower strength compared to OHT specimens. The strength retention of carbon fiber/epoxy composites with open holes was 66%. Delamination initiation at the hole's edge caused a reduction in the stress concentration factor. Filling the hole with a bolt suppressed this relieving mechanism, leading to lower strength in BJT specimens compared to OHT specimens. Bolt joint efficiency was calculated as 15%. The reduction in strength in bolted joints was attributed to fiber-matrix splitting and delamination, aligning with Hart Smith's bolted joint efficiency diagram. These findings contribute to materials selection and structural reliability estimation for carbon fiber/epoxy composites. They highlight the behavior of open hole and bolt joint configurations under tensile loading, providing valuable insights for engineering applications.