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Journal ArticleDOI

Understanding of logic in ladder program with its transformation into sequential graph using state space-based approach

22 May 2013-International Journal of Mechatronics and Manufacturing Systems (Inderscience Publishers Ltd)-Vol. 6, Iss: 2, pp 159
TL;DR: In this article, an approach to understand the logic in ladder diagram (LD)/LD program by transforming it into a sequential function chart (SFC) is presented, which employs state-space-based approach and rule-based heuristics.
Abstract: This paper presents an approach to understand the logic in ladder diagram (LD)/LD program by transforming it into a sequential function chart (SFC). Transformation of LD into SFC is done by employing state-space-based approach and rule-based heuristics. State space approach generates all possible states of the system, being controlled by LD, by assuming the occurrence of various events in the manufacturing system in an asynchronous manner. From all these states, practically feasible states that conform to heuristic rules developed for various control elements in the system are identified. From these feasible states, the sequence of occurrence of states, i.e., sequence graph is derived by a heuristic that relies on the essential input conditions activating each output in the LD. The effectiveness of the proposed approach is demonstrated with several case studies, representing increasing levels of logical complexity in the respective ladder diagrams.
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Proceedings ArticleDOI
01 Jul 2017
TL;DR: This work provides analysis on the main algorithms for extracting the sequential logic from a Ladder Diagram program that can be found in the literature and proposes a new algorithm to extract the sequential Logic and produce a state-machine from a LD program.
Abstract: Still to this day, there are many industrial sequential processes described in Ladder Diagram (LD), a language not suitable for that purpose, that can be described in SFC, a proper language for describing sequential processes. We provide analysis on the main algorithms for extracting the sequential logic from a LD program that can be found in the literature and point some problems in them. We then propose a new algorithm to extract the sequential logic and produce a state-machine from a LD program. We describe a tool developed to implement said algorithm and show the results.

1 citations


Cites methods from "Understanding of logic in ladder pr..."

  • ...[5] take an approach based on the extraction of all possible states from the Ladder Diagram, creating a state space that can be trimmed by simple heuristic rules defined by the user....

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Dissertation
13 Jul 2017
TL;DR: A tool to extract sequential logic from LD programs and represent it in SFC is developed in Java programming language, which is a graphical language designed to break sequential control into small tasks and can be easily understood upon quick analysis.
Abstract: Ladder Diagram is a simple graphic language useful to express control in terms of a set of boolean predicates that relate input boolean data to output actuation. Although widely used, LD is not properly designed to express sequential logic. To express sequential logic in a clear and structured way we can use SFC. SFC is a graphical language designed to break sequential control into small tasks and can be easily understood upon quick analysis. Since many industrial processes are sequential by nature and there are still many LD programs in the industry, a tool to extract sequential logic from LD programs and represent it in SFC is needed. From this premise, a software tool is developed in Java programming language. This tool takes a project in PLCopen XML format, extracts the LD program and creates the smaller state-space that represents the obfuscated sequential logic. From this state-space a SFC can be built.

Cites background or methods from "Understanding of logic in ladder pr..."

  • ...They also refer [2], stating that developing temporal models and the arbitrary selection of initial state "hamper the use of this approach for any pratical problem" [19]....

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  • ...[19] Considering the previous example (figure 2....

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  • ...3 Extraction of implicit sequential logic with state-space based approach The third algorithm, by Nandhan & Babu [19], is a state-space based, computing-driven approach....

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  • ...Nandhan & Babu [19] refer the work of Falcione & Krogh [3], stating that the algorithm is not mature to deal with pratical cases....

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  • ...The algorithm can be broken in three parts [19]:...

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