Real-Time Reactions in Supervisory Control According to Data Freshness

Supervisory control systems in plants mustacquire data without any loss and react for state changes. Someof state change should be reacted in a real-time manner, whileothers may be notified in a best-effort manner. To implementa middleware which works as a server in supervisory control systemsin an acceptable cost, we value the data freshness which meanshow much time has passed from the occurrence of the data. Inthis paper, we present the Active Ring model whichincorporates the ECA mechanism into circular areas. With rulesusing only the latest data, the ECA mechanism realizes time-criticalreactions as firm real-time tasks. In addition to that, the rulestrigger best-effort notification which is realized as a softreal-time task. The middleware works in numerous plants for steelmill, water purifying, and tunnel ventilation. This paper includesan experimental result revealing that the ActiveRing model is effective to provide service according to the datafreshness.