A Framework for Control-Reconfiguration Following Fault-Detection in Discrete Event Systems ⋆

We introduce a framework for control-reconfiguration in discrete event systems that performs fault-detection and then reconfigures the control to ensure that certain desired specifications are met. The controlled system has separate specifications prior to a fault versus after a fault (to allow for any changes in the specification owing to the occurrence of a fault). Prior to the occurrence of a fault, a certain controller is applied so as to ensure a given pre-fault specification. The same controller is continued to be used even after a fault and until its detection. Once a fault is detected, the control is reconfigured. All along the postfault duration (prior to as well as after reconfiguration), the controlled system is required to satisfy a give post-fault specification. We mathematically formulate the above control problem and provide a condition for reconfigurability. We also establish the condition for the limiting case where control-reconfiguration is not required. Also, we introduce the notion of degree of disambiguability of faulty traces which when increased, increases the ability to meet the control requirements of preand postfault specifications.