Representing Control Software Functionality as Part of a Modular, Mechatronic Construction Kit

automated Production Systems (aPS) are highly complex mechatronic systems with lifetimes of up to 50 years. The lack of advanced software engineering methods in industrial automation often causes historically grown legacy code with low quality. Modeling and refactoring of legacy control software are considered as inevitable to manage ever-increasing software complexity and face upcoming challenges in the context of Industry 4.0. However, promising goals such as mechatronic modularization, product line engineering, or variability management have up to now hardly made their way to control software in aPS. To address this gap, the main contribution of this paper is a concept of function-oriented software modeling for aPS. The approach provides three models to map control software in aPS to the implemented system functionalities on code level, by also considering extra-functional software tasks that cannot be directly mapped to the physical modules. The models are implemented using ME-TUS software, i.e., a renowned tool for modeling and optimizing mechatronic system architectures based on a function-oriented construction kit principle. The modeling approach is evaluated with industrial and academic experts with promising results.