Implementing a PLC-Service bus with IEC 61499
Virendra Ashiwal, Antonio M. Gutierrez, Alois Zoitl · 2022
With an increased demand for customization, a better quality of products, and available variability in machines, enforcing machine developers to rethink how PLC-software is structured and developed. It demands the PLC-software to be adaptable, flexible, and modular. Current PLC-software uses global variables for interaction between its program organization units (POUs). Global variables increase tight coupling and reduce adaptability, flexibility, and modularity. A new architectural concept, the PLC-Service bus, was suggested to address this issue. To reduce coupling, POUs and software components of the PLC communicate via a service bus. This concept leads to two problems. There are no standard models to describe these interactions clearly, and there is no implementation of the PLC-Service bus to develop PLC-software based on message interaction patterns (MIPs). This paper uses the capping station from the VDMA R+a OpcUA Demonstrator as a running example. With an Event-driven process chain model (EPC), we describe the interactions between various software components of the capping station to identify MIPs. Based on these MIPs, we implement the PLC-software of the capping station with IEC 61499.