Robust corrective control of asynchronous sequential machines with control input and feedback faults

Fault tolerance for asynchronous sequential machines (ASMs) is studied in the framework of corrective control theory. The considered ASM is subjected to adversarial inputs entering the closed-loop system through control input and state feedback channels. If the adversarial input occurs at the control input channel, the machine undergoes unauthorized state transitions. If the adversarial input occurs at the feedback channel, it distorts the state feedback value that is transmitted to the controller. We present a scheme of fault diagnosis on each fault event and the existence condition and design procedure for a corrective controller that invalidates any fault occurrence in an asynchronous mechanism. An illustrative example is provided to validate the proposed fault diagnosis and fault tolerant control methodology.