Switched control of uncertain nonlinear process systems subject to control and communication constraints

This paper presents a switched control strategy for the robust stabilization of uncertain nonlinear process systems with both control and measurement sampling constraints. A model-based constrained Lyapunov-based controller is initially designed for each control actuator configuration. Next, the constrained stability regions and the terminal sets of all the configurations are characterized, in terms of the size of the control constraints, the sampling period and the plant-model mismatch, and analyzed. The analysis shows that the configuration with the largest stability region does not necessarily have the smallest terminal set, which leads to a conflict with the desired control objective of steering the process from a large initial state to a small terminal neighborhood of the equilibrium point. To resolve this conflict and attain the desired control objective, a switching strategy that executes a sequence of transitions between the available actuator configurations is developed. The key idea of the switching logic is to keep a configuration active until its terminal set is reached and then to switch to another stabilizing configuration with a smaller terminal set. The proposed robust hybrid control method is illustrated using a chemical process example.