Dynamic Quasi-Decentralized Control of Networked Process Systems with Limited Measurements

This work presents a quasi-decentralized networked control structure with a dynamic communication logic for plants with limited state measurements and interconnected units that exchange information over a shared, resource-constrained communication network. Initially, an observer-based output feedback controller is synthesized for each unit, and Lyapunov techniques are used to explicitly characterize the closed-loop stability properties of each unit under continuous communication. This characterization is then used as the basis for developing a dynamic communication strategy that keeps the information transfer between the local control systems to a minimum without jeopardizing closed-loop stability. The key idea is to monitor the evolution of the observer-generated state estimates locally within each unit and suspend communication for as long as the expected stability threshold is met. During periods of communication suspension, each control system relies on a set of models that provide estimates of the states of the neighboring units. At times when the stability threshold is breached, communication is re-established and the neighboring units are prompted to send their data over the network to update the models. The stability threshold is determined using Lyapunov techniques and can be tightened or relaxed by proper controller and observer tuning. Finally, the stability and performance properties of the dynamic networked control structure are illustrated using a chemical plant example.