Design and evaluation of event-driven networked real-time control systems with IEC function blocks

The control delay holds a significant impact on the quality of control (QoC) of a networked control system (NCS), degrading QoC and even causing system instability. With an objective of performance optimization through minimizing control delay, an event-driven approach to NCS design is proposed. The function block model defined in IEC61499 is extended and employed as the component for constructing event-driven NCS. Effective design principles integrating the scheduling methodology of pipelining are presented. The NCS design for a DC servo system illustrates the proposed design principles. The impact of control period on QoC is visualized, and the optimal working range of control period is obtained. The QoC of NCS is measured by a general performance criterion. Simulation results for performance evaluation show that our approach leads to better QoC than the sequential system does.