A hierarchical and concurrent approach for IEC 61499 function blocks

The IEC 61499 function block standard proposes a new specification language for describing distributed industrial control systems. The standard specifies the use of an execution control chart (ECC) for state control, with algorithm calls for data handling. The design of complex industrial systems such as baggage handling systems can be difficult because of large state-spaces or complicated component interactions. Additionally, the flat state machines used in the standard do not provide a simple method for specifying error handling within the process´s execution. State machines from synchronous languages, however, have hierarchy and concurrent constructs to aid the developer. This paper presents a hierarchical and concurrent extension to ECCs, which we call HCECCs, which presents new design constructs adapted from synchronous languages in order to improve system specification with function blocks. The semantics of HCECCs, which are backward compatible with the standard, are described and design using HCECCs is compared with other specification approaches.