RSimplex: A robust control architecture for cyber and physical failures

As the complexity of Cyber-Physical Systems (CPS) increases, it becomes increasingly challenging to ensure CPS reliability, especially in the presence of software and/or physical failures. The Simplex architecture is shown to be an efficient tool to address software failures in such systems. When physical failures exist, however, Simplex may not function correctly because physical failures could change system dynamics and the original Simplex design may not work for the new faulty system. To address concurrent software and physical failures, this article presents the RSimplex architecture, which integrates Robust Fault-Tolerant Control (RFTC) techniques into the Simplex architecture. It includes the uncertainty monitor, the High-Performance Controller (HPC), the Robust High-Assurance Controller (RHAC), and the decision logic that triggers the switch of the controllers. Based on the output of the uncertainty monitor, we introduce a monitor-based switching rule in the decision logic in addition to the traditional envelope-based rule. The RHAC is designed based on RFTCs. We show that RSimplex can efficiently handle a class of software and physical failures.