• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.706-709
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• 1996

In this paper, an algorithm for PLC(Programmable Logic Controller) fault diagnosis system is proposed and experimentation is conducted with a PLC and a virtual plant. Wrong output backward tracking algorithm is proposed in order to find the external faults of PLC. And query with keywords of the fault systems and specially designed test sequence programs are used. We lay emphasis on the backward tracking algorithm to diagnose the faults of PLC. It is shown experimentally that the proposed algorithm can find the faults which a typical self diagnostics in the-commercially available PLC cannot.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.197-200
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• 2002

This paper is about a system development which control and monitor a PLC of the remote-distance through the Internet using the web-browser. In general, the PLC uses its own communication protocol of PLC Manufacture. It is actually impossible to be used through the Internet, because the PLC communication protocol is basically developed to be suitable for short-distance. Therefore, what we need is a transformation system which can convert the PLC communication protocol into the form which can connect to the Internet. In that sense, this paper is that about remote-control method through the WWW ( World Wide Web ). This system have three characteristics. First, it is possible to connect the Internet directly irrespective of CPU, Operating system and browser. Second, it is easy for user to access and treat. Third, it needs only HTML to operate without java or plug-in expansion. In this paper, we will introduce the monitoring and control system of PLC on the Linux with the Apache web-server.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.5
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• pp.78-85
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• 2006

Thanks to the spacial and timely flexibility of laboratory's environment, the distance learning based real time PLC education system has been brought into relief as a next generation laboratory alternative. The developed system was installed using a relatively cheap PLC and PC camera. Providing image feedback through the PC camera, the system provides the student's interests of the lab as well as an opportunity to monitor the lab's activities and results.

• Korean Journal of Computational Design and Engineering
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• v.14 no.1
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• pp.50-59
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• 2009

There are two main problems in the current PLC ladder programming practices: First, currently there are no widely adopted systematic design methods to deal with PLC based control systems in the shop floor. So, the control logic design phase is usually omitted in current PLC programming development life cycle. Second, PLC ladder logic provides only microscopic view of system processes. As a result, it is difficult for FA engineers to have overall perspectives about the interaction of system components intuitively during the verification step of logic errors. To solve these problems, this paper proposed object-oriented design and automatic generation method of PLC ladder logic. Based on the proposed method, the computer software to assist the automatic ladder logic generation is also developed.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.8
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• pp.647-650
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• 2003

PLC (Power Line Communication) is the communication method using the existing power line installed in houses and offices to convert and transmit high frequency communication signal from tens of KHz to tens of MHz, and receive the filtered signal using high frequency filter The advantage of PLC is that PLC uses the existing power line installed in houses and offices so it does not require separate power line. Easy and convenient access using electric outlets is another advantage of PLC. However, PLC has some disadvantages such as limited transmission power, high load interference and noise, variable signal attenuation, characteristic of impedance, and selective possibility of frequency property. We designed the boiler temperature control system unit by using the PLC modem. We can avoid unnecessary heating of separate temperature control unit, and save the cost accordingly control stability of the proposed system is proven through the experiment.

• Korean Journal of Computational Design and Engineering
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• v.14 no.5
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• pp.323-329
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• 2009

Auto-makers can only remain competitive by producing high quality vehicles in an efficient way. In designing a production line, one of the most important objectives of digital manufacturing is to verify design errors as early as possible. In terms of the cost and time saving, it is very essential to start the construction of a production line with a proven design which is error-free. Likewise, this paper aims to implement PLC verification using an example. The verification in automobile manufacturing means verifying PLC program, which control automatic devices. In this paper, we built a virtual factory to implement PLC simulation and introduced verification procedure using PLC Studio. Finally, we can prove the availability for the PLC verification.

• Proceedings of the KIEE Conference
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• 2005.11c
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• pp.8-13
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• 2005

공장(정)자동화에 대한 산업현장의 요구가 증대되고 다양한 자동제어 기술이 발전, 적용되면서 이 분야에 대한 중요도는 날로 커져가고 있다. 산업설비 및 공정 자동화에 가장 널리 적용되고 있고 중추적인 역할을 수행하고 있는 제어기가 바로 프로그래머블 논리 제어장치, PLC이다. 그러나 PLC 프로그램을 작성하여 실제로 기계나 설비에 적용하기 위해서는 PLC 프로그램의 논리적인 오류 등을 검사하고 수정하는 등의 작업이 필요한데 자동화 시스템에서 이를 직접 적용하기에는 많은 위험부담과 비용부담이 뒤따른다. 한편, 눈부신 발전을 거듭한 PLC 제어 기술에 데한 전문지식을 보유한 인력에 대한 산업현장의 요구는 꾸준히 지속되고 있는 추세이나 지금까지 교육기관에서 실시되고 있는 PLC 제어기술에 관련된 교육은 해당 시스템에 대한 거시적 이해 위주의 이론교육 형태로 실시되어 왔다. 이러한 산업적 측면과 교육적 측면의 문제점을 해결하고 자동화, 자동제어 교육에 대한 학생들의 흥미와 실무능력 향상을 위하여 본 논문에서는 현장에서 활용되고 있는 기기와 시스템을 모의할 수 있는 자동화 설비의 가상 플랜트 시뮬레이터와 PLC 프로그램을 편집하고 모니터할 수 있는 도구를 개발하여 종합적이고 현장감 있는 교육을 가능하게 하는 방법을 제안하였다.

• Journal of KIISE
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• v.43 no.5
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• pp.569-578
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• 2016

The PLC (Programmable Logic Controller) has been widely used for the development of digital control system of nuclear power plant. The PLC has high maintenance costs and increasing complexity, hence, FPGA (Field Programmable Gate Array) based digital control system has been considered as an alternative. However, the development of FPGA based digital control system is a challenge for PLC engineers because they are required to learn about new language to develop FPGA and knowledge and know-how acquired in the development of PLC is not transferable. In this study, we proposed and implemented an automatic translation tool for translation of FBD (Function Block Diagram), a programming language of PLC software, into VHDL (VHSIC Hardware Description Language). Automatically translating the FBD to VHDL using this tool allows PLC engineers to develop FPGA without any knowledge of the hardware description language.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.101-106
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• 2010

Due to significant advances in Internet technology, there have been many e-learning courses offered by universities and academic institutes nowadays through the Internet. And these courses have benefited many students who might be constrained by distance and time. Nevertheless, most web-based courses are lecturing courses that cannot fulfill the needs for engineering technology education. In this paper, we propose the design and implementation of web-based programmable logic controller(PLC) laboratory to support learning and training for industrial automation. The proposed web-based PLC laboratory system consists of virtual labs and remote labs. This web-based PLC laboratory can be accessed by registered students to practice PLC experiments at their own home, enhancing the quality of education without much increasing in the overall cost. With the help of web cameras, the students can even have experience the live PLC experiments through the Internet.

• 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.