Automated production systems (aPS) are complex systems with high reliability standards which can -besides through traditional testing -be ensured by verification using formal methods. In this paper we present a development process for aPS software supported by efficient formal techniques with easy-to-use specification formalisms to increase applicability in the aPS engineering domain. Our approach is tailored to the development of evolving aPS as existing behavior of earlier revisions is reused as specification for the verification. The approach covers three verification phases: regression verification, verification of critical interlock invariants and delta specification and verification. The approach is designed to be comprehensible by aPS software engineers: Two practically applicable specification means are presented. Formal methods have not yet been widely adapted in industrial aPS development since they lack (a) scalability, and (b) concise and comprehensible specification means. This paper shows concepts how to tackle both issues by referring to existing behavior during evolution verification to advance towards the goal of applicability in the aPS engineering domain.A laboratory case study demonstrates the feasibility and performance of the approach and shows promising results.

With recent trends in manufacturing automation, such as Industry 4.0, control software in automated production systems becomes more and more complex and volatile, complicating and increasing importance of quality assurance. Test tables are a widely used and generally accepted means to intuitively specify test cases for automation software. However, each table only specifies a single software trace, whereas the actual software behavior may cover multiple similar traces not covered by the table. Within this work, we present a generalization concept for test tables allowing for bounded and unbounded repetition of steps, "don't-care" values, as well as calculations with earlier observed values. We provide a verification mechanism for checking conformance of an IEC 61131-3 PLC software with a generalized test table, making use of a state-of-the-art model checker. Our notation is inspired by widely-used paradigms found in spreadsheet applications. By an empirical study with mechanical engineering students, we show that the notation matches user expectations. A real-world example extracted from an industrial automation plant illustrates our approach.

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