How object-oriented design principles enhance the development of complex automation programs - A Best Practice Paper on how to develop service-interfaces for process modules as defined in VDWDE/NAMUR 2658

摘要

The complexity and difficulty for designing and developing automation programs based on the IEC 61131-3 [1] is continuously increasing. With the VDI/VDE/NAMUR 2658 [2] a new level of complexity will be reached - control modules with more complex interfaces, services as functional capsulation in process operations and interdependencies to other unknown up- or downstream modules. In these applications, the proven procedural approach reaches its limits. The object-oriented paradigm could be the solution. However the object-oriented extension of [1] is not supported in many available plc development tools. This results in a low acceptance and low experience in object-oriented thinking by plc developers. This paper will be focused on an object-oriented motivated transformation of design principles and patterns into StructuredText. The results are demonstrated in form of a best practice implementation for programs compliant to [2]. The presented approach does not use any kind of supportive or generating tools, it's based completely on the possibilities of IEC 61131-3.