Carlo Veber

This paper contributes to the ongoing development of comprehensive execution semantics of IEC61499 by discussion and comparison of the semantics that could be achieved by alteration of postulates introduced in the Sequential Hypothesis, and by variation of different priority assignments during implementation.

Most applications in industrial automation could be hazardous for people, plant and environment. Therefore it is necessary for related distributed control systems, implementing safety functions for such applications, to rely on a real-time and fault tolerant communication among all connected stations. To realise this objective, safety related networks should be realised using Ethernet-based protocols with additional layers involved to fulfill safety requisites. The paper investigates the state of art technology of Ethernet-based safe communication systems with special attention to functional safety network requirements defined by the IEC 61508, pointing out the problems and examining how these communication protocols satisfy the defined requirements.

The paper deals with the implementation of IEC 61499 applications into executable code. In particular, this work concerns the automatic conversion of a IEC 61499 application into an AWL application executable on a standard Siemens PLC. The IEC 61499 Standard defines an application as a network made of Function Blocks and event/data connections. The behaviour of a single Function Block and of an application is also specified in the standard. At the moment, there are no industrial solutions supporting this standard: from that the need to cover the gap between the standard and the existing legacy devices.