• Journal of the Korea Safety Management & Science
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• v.12 no.2
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• pp.65-73
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• 2010

In an automated industry PLC plays a central role to control the manufacturing system. Therefore, fault free operation of PLC controlled manufacturing system is essential in order to maximize a firm's productivity. On the contrary, distributed nature of manufacturing system and growing complexity of the PLC programs presented a challenging task of designing a rapid fault finding system for an uninterrupted process operation. Hence, designing an intelligent monitoring, and diagnosis system is needed for smooth functioning of the operation process. In this paper, we propose a method to continuously acquire a stream of PLC signal data from the normal operational PLC-based manufacturing system and to generate diagnosis model from the observed PLC signal data. Consequently, the generated diagnosis model is used for distinguish the possible abnormalities of manufacturing system. To verify the proposed method, we provided a suitable case study of an assembly line.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.153-158
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• 1997

This paper describes a formal safety analysis technique which is demonstrated by performing empirical formal safety analysis with the case study of beamline hutch door Interlock system that is developed by using PLC(Programmable Logic Controller) systems at the Pohang Accelerator Laboratory. In order to perform formal safety analysis, we have built the Z formal specifications representation from user requirement written in ambiguous natural language and target PLC ladder logic, respectively. We have also studied the effective method to express typical PLC timer component by using specific Z formal notation which is supported by temporal history. We present a formal proof technique specifying and verifying that the hazardous states are not introduced into ladder logic in the PLC-based safety critical system.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.1
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• pp.53-59
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• 1996

An automatic verification method has been studied to determine the safety and operability of programmable logic controller (PLC) based systems. For the systematic and efficient verification, we have developed a conversion method from relay ladder logic (RLL) to the verification system description. RLL is a common representation used to document PLC programs for the sequential logic of the system such as the safety interlocks and the startup/shutdown procedures. Once the modules are developed, complex RLLs can be represented by the combination of modules. As a result we can verify complex PLC systems using the verification method including RLL modules. The developed modules are used to verify alarm systems and show that the method is valid.

• Journal of the Korea Safety Management & Science
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• v.17 no.1
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• pp.179-192
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• 2015

In an automated industry PLC plays a central role to control the automation system. Therefore, fault free operation of PLC controlled automation system is essential in order to maximize a firm's productivity. A prior test of control system is a practical way to check fault operations, but it is a time consuming job and can not check all possible fault operation. A formal verification of PLC program could be a best way to check all possible fault situation. Tracing the history of the study on formal verification, we found three problems, the first is that a formal representation of PLC control system is incomplete, the second is a state explosion problem and the third is that the verification result is difficult to use for the correction of control program. In this paper, we propose a transformation method to reproduce the control system correctly in formal model and efficient procedure to verify and correct the control program using verification result. To demonstrate the proposed method, we provided a suitable case study of an automation system.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2601-2604
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• 2003

원전 안전계통에 적용될 PLC는 엄격한 내진, 전자파, 내환경 시험기준을 만족해야 하며, 원전 안전등급에 부합되는 안전성 및 신뢰성을 만족해야 한다. 전 세계에서 안전계통에 적용될 PLC는 Siemens 의 Teleperm XS, Invensys 의 Triconex, WestingHouse 의 AC-160 이 있으며, 국내에서는 원전 안전계통 개발시 전적으로 이들 PLC 수입에 의존하고 있다. 현재 한국원자력연구소와 국내 PLC 제조회사간에 공동과제를 통해 안전등급 PLC 개발을 수행하고 있으며, 본 논문에서는 개발될 PLC 의 설계기준과 개발된 하드웨어 및 소프트웨어 사양 등 개발현황에 대해 기술한다.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.291-292
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• 2007

This paper deals with the design of control cabinet based on safety PLC for Control Rod Control System(CRCS). The CRCS controls the operation of the CRDMs(Control Rod Drive Mechanisms). The CRDM moves the control rods which regulate the reactor power. vertically in the reactor core. The Control Cabinet in CRCS makes and conveys control signals to the power cabinet which provides power to the CRDM. We designed the Control Cabinet, based on POSAFE-Q, safety PLC. The application programs working in PLC can be programmed by pSET(POSAFE-Q Software Engineering Tool), Identified Development Environment.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1630-1631
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• 2007

This paper deals with the design of control cabinet based on safety PLC for reactor power control system(PCS). The PCS controls the operation of the CEDMs(Control Element Drive Mechanisms). The CEDM moves the CEAs(Control Element Assemblies) which regulates the reactor power, vertically in the reactor core. The Control Cabinet in PCS makes and conveys control signals to the power cabinet which provides power to the CEDM. We designed the Control Cabinet, based on POSAFE-Q, safety PLC. The application programs working in PLC can be programmed by pSET, Identified Development Environment.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.2
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• pp.365-375
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• 2019

A PLC (Programmable Logic Controller) is a highly-reliable industrial digital computer which supports real-time embedded control applications for safety-critical control systems. Real-time operating systems such as uC/OS have been used for PLCs and must meet real-time constraints. As PLCs have been widely used for industrial control systems and connected to the Internet, they have been becoming a main target of cyberattacks. In this paper, we propose an execution code sanitizer to enhance the security of PLC systems. The proposed sanitizer analyzes PLC programs developed by an IDE before downloading the program to a target PLC, and mitigates security vulnerabilities of the program. Our sanitizer can detect vulnerable function calls and illegal memory accesses in development of PLC programs using a database of vulnerable functions as well as the other database of code patterns related to pointer misuses. Based on these DBs, it detects and removes abnormal use patterns of pointer variables and existence of vulnerable functions shown in the call graph of the target executable code. We have implemented the proposed technique and verified its effectiveness through experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.1
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• pp.1-8
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• 2006

The home network system guarantees families a safe, economical, socially integrated and healthy life by using information appliances. And it provides a family with domestic safety, control of instruments, controllable energy and health monitoring by connecting to home appliances. This study designs the broadband PLC home controller using broadband PLC(Power Line Communication) technology which can save much cost at a network infrastructure by using the existing power line at home. The broadband PLC home controller consists of the broadband PLC module, the embedded main controller module and I/O module. The broadband PLC home controller can control various domestic appliances such as an auto door-lock, a boiler, an oven, etc., because it has various I/O specifications. In this study, selected home network middleware for the broadband PLC home controller is Jini surrogate using Jini technology designed by means of access to easily a home network system without a limitation of the devices. And a client application program is supported java servlet program to manage and monitor the broadband PLC home controller via web browser of a PC or a PDA, etc. Finally, for an application, we implemented and tested a home security system using one broadband PLC home controller.

• Journal of IKEEE
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• v.25 no.1
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• pp.116-127
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• 2021

In this paper, we propose simultaneous control which improve in transient state performance of mechanical parking facilities through simultaneous control of PLC and inverter. In conventional mechanical parking facilities, it is controlled only by PLC, and it is more likely to generate over-currents in induction motors, and the ride comfort is reduced due to wear and damage caused by friction on the brake pads, and the life is shortened. To improve this problems the application of control techniques through simultaneous control of PLC and inverter prevents over-currents in induction motors, protects brake pads, improves ride comfort, increases control and ensures safety. We verify its validity by applying the proposed control method via simultaneous control of PLC and inverter to a mechanical parking facility.