Allocating IEC function blocks for parallel real-time distributed control system

Real-time distributed control systems (RDCSs) have an increasing importance in industrial process. The evolving standard IEC 61499 provides function block (FB) as a suitable metaphor for constructing RDCSs. However, the real-timeliness of such systems has not been well dealt with. From a real-time point of view, the FB model defined in IEC 61499 is extended with several timing characteristics. Task graph (TG) is employed to represent FB based RDCS. By exploiting the benefits of parallelism, pipeline scheduling, which can greatly shorten the control period, is utilized for real-time FBs. The problem of allocating FBs to parallel RDCSs subject to periodicity, time, precedence as well as resource constraints is examined. A heuristic algorithm is proposed to further decrease the minimum of control period while meeting these constraints, thus improving the quality of control (QoC). An illustrative example is presented, highlighting the advantages of the proposed method.