Real time communications in manufacturing

Colloque avec actes et comité de lecture.Manufacturing applications are today distributed and integrated, relying on different types of communication networks to interconnect the different levels of the systems' architecture. This paper discusses the main topics on manufacturing communications from the applications requirements to the most common solutions derived to fulfill them. Temporal and spatial properties of the data to be exchanged are analysed. Data is classified as periodic, aperiodic and sporadic and, for these types, the communication system performance requirements are identified with emphasis on the real-time aspects. A similar discussion is carried on in what concerns the size of data to be transferred per transaction. The use of multimedia and of wide-area communication is also briefly explored. Solutions for different levels of the CIM (Computer Integrated Manufacturing) architecture are identified and an overview of their characteristics is presented. This includes a short description of their organization under the OSI Reference Model and a more detailed discussion on techniques for traffic scheduling. This discussion is mainly focussed on the techniques to control the access to the communications medium and on the use of static or dynamic scheduling. This has essentially in consideration the fulfilment of the data temporal constraints. A short overview of the possibilities opened by the use of Internet in these applications is also included