Fault-tolerant Control of Multi-unit Process Systems Using Communication Networks

This work proposes a methodology for the design of fault-tolerant control systems for chemical plants with distributed interconnected processing units. Bringing together tools from Lyapunov-based nonlinear control and hybrid systems theory, the approach is based on a hierarchical architecture that integrates lower-level feedback control of the individual units with upper-level logic-based supervisory control over communication networks. The local control systems consist each of a family of control configurations connected, via a local communication network, to a local supervisor that orchestrates switching between them on the basis of the stability regions in the event of failures. The local supervisors communicate, through a plant-wide communication network, with a plant supervisor responsible for monitoring the different units and coordinating their responses in a way that minimizes the propagation of failure effects. The communication logic is designed to ensure efficient transmission of information between the units while respecting the inherent limitations in network resources. The proposed approach provides explicit guidelines for managing the various interplays between the tasks of feedback control, switching and communication. The efficacy of the proposed approach is demonstrated through a chemical process example.