Timed fault-tolerant supervisory control

Abstract

In Mulahuwaish,1–4 we investigated the problem of fault tolerance in the framework of untimed discrete-event systems (DES). This approach is different from the typical fault-tolerant methodology as the approach does not rely on detecting faults and switching to a new supervisor; it requires a supervisor to work correctly under normal and fault conditions. This is a passive approach that relies upon inherent redundancy in the system being controlled. In this paper we extend the work of Mulahuwaish1–4 to the timed DES (TDES) setting. We introduce our setting, and then provide a set of timed fault tolerant definitions designed to capture different types of fault scenarios and to ensure that our system remains controllable in each scenario. As the nonblocking property is the same for timed and untimed DES, the untimed fault-tolerant nonblocking properties and algorithms from Mulahuwaish1–4 can also be used in the timed setting without any changes. We then present algorithms to verify these properties followed by complexity analyses and correctness proofs of the algorithms. An example is then provided to illustrate our approach.