Fieldbus Technology and Industrial Automation

All automation systems are now based on fieldbuses. The solutions are numerous due to the number of fieldbuses, which are in turn due to the variety of applications. This paper traces fieldbus technology from its beginnings, which go back to the first industrial networks in the 1970\´s. It analyzes the fieldbus requirements, in terms of functions (or services) and of performance (or quality of service). The three following types of quality of service are studied: transport, timeliness and coherence, according to the different types of traffic to ensure (or to operate). The characteristics of periodic and aperiodic traffic are described. The main international standards (IEC, ISO, CEN) are presented regarding these criteria and the main concepts issued from the OSI model. The architecture of applications and the services of the communication system have a mutual influence. This is an important point for the distribution of the application processes, and will be analyzed in regards to the possible application layer models. The architecture of the communication system itself is also studied in the hopes of finding a single system for all applications. Future developments will be considered, regarding both the end-user needs and the available technologies. And finally, to conclude, we will go back to the title and try to answer the question "Is fieldbus a technology?"