Corrective control of parallel interconnected asynchronous sequential machines with output feedback

The problem of controlling two parallel interconnected asynchronous sequential machines (ASMs) by a single corrective controller is studied. The objective is to realise immediate recovery against transient faults that cause unauthorised state transitions to each ASM. Since only output feedback is available to the controller, the correction procedure must be able to accommodate state uncertainty underlying the composite machine. A computationally efficient scheme of controller synthesis is presented in the framework of corrective control theory. To validate the practicality of the scheme, the authors apply the proposed controller to a faulty asynchronous FPGA system in parallel connection. Experimental results confirm the instantaneous fault recovery of the closed-loop system.