• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.2
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• pp.207-215
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• 2004

The PLC programming by IEC1131-3 is hard to handle to ordinary users as well as professionals. Also it has not a generality, so that it couldn't be debugging some logic errors easily. In order to be adapted for such environment, In this paper, I have developed the ISPLC(Intelligent Agent System based Software Programmable Logic Controller). In ISPLC system, LD programmed by a user is converted to the C code which can be used in a commercial editor such as Visual C++. The detection of logical errors in C code is more effective than PLC programming itself. ISPLC provides the GUI-based interface in web environment and an easy programming platform to such beginners as well as professionals. The study of code conversion of LD to IL as well as IL to C is firstly tried in the world as well as KOREA. To show the effectiveness of the developed system, I applied it to a practical case, a real time traffic control system. ISPLC is minimized the error debugging and programming time owing to be supported by windows application programs.

• Journal of IKEEE
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• v.23 no.2
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• pp.487-494
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• 2019

In this paper, we designed IOT(Internet of Things) based hydroponic plant factory in order to avoid the effects of fine dust penetrating into the soil, and proposed the PLC(Programmable Logic Controller) control methods. The designed plant factory could monitor the density of oxygen, the density of nutrient solution, temperature and humidity through touch screen and smart phone, and control the heater and cooler, ventilation and dehumidifier, and wavelengths of LEDs to grow plant in appropriate environments.

• Journal of Bio-Environment Control
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• v.4 no.2
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• pp.203-210
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• 1995

Using the programmable logic controller (PLC), a kind of microcomputer, a facility to control EC and pH automatically in nutriculture of tomato was developed. A program for the automatic control of nutriculture was written in ladder diagram language. EC and pH levels of nutrition solution could be maintained at 1.70-1.72 and 6.1-6.5, respectively, during the entire growing period. Better fruits and higher yield were obtained in automatic control plot than in the control plot. Inorganic elements in plant were higher in the former than in the latter.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.10
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• pp.1117-1123
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• 2014

Nuclear industries have faced unfavorable circumstances such as an obsolescence of the instrumentation and control system, and therefore nuclear society is striving to resolve this trouble fundamentally. FPGAs are currently highlighted as an alternative means for obsolete control systems. Because of the obsolescence-unaffected characteristics, FPGA should be highly reliable in order to be a replacement for PLC (Programmable Logic Controller). Therefore, it is necessary to establish a software development aspect strategy that enhances the reliability of an FPGA-based controller. The reliability analysis including the MTBF (Mean Time Between Failures) is carried out based on the MIL-HDBK-217F. MTBFs are compared with the FPGA-based controller COMMON-Q PLC. As an analysis result, it shows that the reliability of the FPGA-based controller is better than or equal to that of PLC.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.741-749
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• 2014

This paper proposes a machine vision module for PLCs (Programmable Logic Controllers). PLC is the industrial controller most widely used in factory automation system. However most of the machine vision systems are based on PC (Personal Computer). The machine vision system embedded in PLC is required to reduce the cost and improve the convenience of implementation. In this paper, we newly propose a machine vision module based on PLC. The image processing libraries are implemented and integrated with the PLC programming tool. In order to interface the libraries with ladder programming, the ladder instruction set was also designed for each vision library. By use of the developed system, PLC users can implement vision systems easily by ladder programming. The developed system was applied to sample inspection system to verify the performance. The experimental results show that the proposed system can reduce the cost of installing as well as increase the ease-of-implementation.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.8
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• pp.836-844
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• 1991

PLC(programmable logic controller) system is widely used for the control of factory. PLC system receives ladder diagram which is drawn by the user to implement hardware logic, converts the ladder diagram into sequence program which is executable in the PLC system, and executes the sequence program indefinitely unless user breaks. The sequence program processes the data of on/off signal, and endures 1 scan delay and missing of pulse-type signal shorter than a scan time. So, data dependency doesn't exist. By applying theis characteristics to multiprocessor architecture, we design parellel PLC functionally and evaluate performance upgrade. Parallel PLC consists of central processing module, N general processing unit, and a shared memory by master-slave type. Each module executes allocated sequence program by the control of central processing module. We can expect performance upgrade by parallel processing, and reliability by relocation of sequence program when error occurs in processing module.

• Journal of Power System Engineering
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• v.8 no.1
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• pp.62-68
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• 2004

This paper describes a fault tolerant control in distributed PLC(Programmable Logic Controller) system to ensure reliability of controllers which have some faults simultaneously. First, the behavior of PLC is modeled as discrete expressions using Galois field. Then, we design the control laws for additional spare controllers to generate parity code with two dimensions. Finally, the algorithm for estimating normal output instead of abnormal output from the controllers with fault is suggested. Comparing to the traditional duplication method, the suggested method can reduce the number of spare controllers significantly to ensure control reliability. This method will be applied to an automatic system in order to increase reliability. Also, it can improve cost performance of the system.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.1012-1017
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• 1993

In this paper, the instruction set and the architecture of a RISC processor for programmable logic controller is suggested. From the measurement of existing programs, the characteristics of ladder instructions are analyzed. The instruction set is defined so that the existing ladder program can be reused with simple translation. Because bit instructions controls the behavior of word instructions, the processor suits for high level language like SFC. Simulations show that the PLC with the suggested processor is twenty times faster than the PLC with the multi-purpose microprocessor.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2402-2404
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• 1998

This paper proposes a translation method that converts ladder diagrams to binary executable codes for PLC (programmable logic controller)s. A PLC based on general purpose DSP(digital signal processor) validates the method. We performed a benchmark on the system that compares the execution time of the interpretation method and ours. Experimenal result shows how fast this method executes programs that consist of codes generated.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.47-52
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• 2000

Redundant programmable logic controllers are used in practice with the aim of achieving a higher degree of availability or fault tolerance. Redundancy system is fault tolerant programmable logic controller for machine and plant. It is event synchronized master-standby system with a 2 channel(1-out-of-2) structure. A data link connects line the master to the standby controller.Fault tolerant systems should always be used when it is necessary to keep the probability of a total control system failure to a minimum. The objective of using high availability programmable logic controller is a reduction of losses of fault tolerant system are quickly compensated by the avoidance of loss of production.