Time critical communication networks: field buses

The introduction of field buses to replace the traditional wiring of sensors and actuator to programmable controllers is discussed. After a brief summary of the advantages presented by field buses, the features of the interconnected devices, and the requirements that these networks must fulfill are examined. A description is given of PHOEBUS, a prototype field bus developed for a machine tool. This implementation is compared to other proposals. An architecture based on the OSI reference model is presented with elements of services and protocols that match the requirements for a machine tool field bus. A series of problems that are introduced when several pieces of automation equipment share the same field bus is considered.<>