On detectability and recoverability of input/state asynchronous sequential machines with transient faults in non-fundamental mode

—Corrective control has been successfully applied to compensating for faulty behaviors of asynchronous sequential machines. In this paper, a corrective control scheme is studied for dealing with transient faults that may happen in non-fundamental mode operations. Since a fault can occur to a machine in transient transitions, the procedure of fault diagnosis and fault tolerant control should be more complicated compared with the case of fundamental mode. We show that certain properties, called detectability and recoverability, are requisites for the existence of a fault tolerant corrective controller that makes the closed-loop system immune against any fault occurrence in non-fundamental mode. A simple example is provided to illustrate the proposed notions and the controller existence.