Ben Lukoschus

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Programmable Logic Controllers (PLC) are widespread in the manufacturing and processing industries to realize sequential procedures and to avoid safety-critical states. For the specification and the implementation of PLC programs, the graphical and hierarchical language Sequential Function Charts (SFC) is increasingly used in industry. To investigate the(More)
Programmable Logic Controllers (PLC) are widely used as device controllers for assembly lines, chemical processes, or power plants. Sequential Function Charts (SFC) form one of the main programming languages for PLCs and, therefore, the correctness of the PLC software implemented as SFCs is crucial for a safe operation of the controlled process. A(More)
Sequential function charts (SFCs) are defined as a modeling language in the IEC 1131-3 standard [1] and can be used to structure and drive programmable logic controllers (PLCs). It includes interesting concepts as hierarchy, history variables and priority. As the typical application area of this language is the control of industrial processes, it is obvious(More)
While formal verification has been successfully used to analyze several academic examples of controlled hybrid systems, the application to real-world processing systems is largely restricted by the complexity of modeling and computation. This contribution aims at improving the applicability by using decomposition and deduction techniques: A given system is(More)
In this paper, several aspects of the composition of discrete state condition/event systems according to Sreenivas and Krogh are discussed. We introduce a new composition operator called parallel interconnection. It is shown to be a generalization of the originally defined cascade and feedback operators. Based on this composition operator, a modular(More)
Programmable logic controllers (PLCs) occupy a big share in automation control. However, hardly any validation tools for their software are available. In this work we present a lightweight verification technique for PLC programs. In particular, static analysis is applied to programs written in Instruction List, a standardized language commonly used for PLC(More)
The algorithmic analysis of control systems for large and distributed hybrid systems is considerably restricted by its computational complexity. In order to enable the verification of discrete controllers for such hybrid systems, this contribution proposes an approach that combines decomposition, model checking and deduction. The system under examination is(More)