Model-driven re-engineering of control applications

Abstract

Many small and medium sized companies in Europe face the problem of running their automation plants with 20-year-old control hardware no longer supported by their suppliers. Due to recurrent hardware aging these companies are forced to gradually replace their control devices by new components that are not always compatible with their current control system. By integrating new control devices into their current control system they are faced with the choice between partly control hardware replacement and control hardware replacement as a whole. Running old and new control systems in parallel causes increasing overhead in managing the different control software systems. A number of different control software systems also might increase the need for repetitive hardware changes. Setting up the control software as a whole provides the opportunity to find a more flexible solution which supports replacing components in a more convenient way than the current International Electrotechnical Commission (IEC) 61131 standard based solutions allow. The great disadvantage of a replacement as a whole is the fact that the affected companies already spent lots of money on developing their current IEC 61131 based control systems and therefore they usually do not want to start again from scratch. This thesis presents a solution to this apparent dilemma, it provides an automatic re-engineering method of current IEC 61131 control systems to new technologies by reuse of existing control code during the renewal process. Based on IEC 61131 the successor IEC 61499 has been defined, which allows the creation of more flexible control systems due to its support of distribution, reconfiguration and vendor independency while simplifying the system design as a whole. IEC 61499 is therefore chosen as the target technology for the aspired re-engineering process. The aspired re-engineering process therefore provides a language migration mechanism that, besides the five languages of IEC 61131, also resolves the vendor dependency of different IEC 61131 dialects. The re-engineering process contains a reverse engineering component to process different IEC 61131 dialects while supporting analysis and refactoring methods to handle the differences. For domain specific languages, such as IEC 61131 and IEC 61499, language development frameworks and model-driven approaches provide an applicable starting point to develop a convenient re-engineering process. To evaluate the resulting re-engineering process two IEC 61131 control applications are re-engineered. The first one is a simulated control application that provides typical features of control systems like reactive behavior on signal changes, statefulness and time-behavior. It tests the basic re-engineering concept for two different vendors and two IEC 61131 languages. The second IEC 61131 control application is an industrial use case since it implements a real plant. This work therefore offers a solution for the recurrent hardware aging by automatically re-engineering the source application to the desired target application. But it also provides an alternative for the third edition of IEC 61131, that performs a change from a domain specific language into a more complex language and even a language similar to a higher programming language, since it is able to convert second edition code into IEC 61499, such that still remains a truly automation specific language.