Handling disturbances with a zone tracking-oriented stabilizing MPC: enlargement of the domain of attraction

Abstract

This work focuses on the hierarchical control structure composed of model predictive control (MPC) and real-time optimization (RTO) layers. Here, a zone tracking-oriented infinite horizon MPC strategy with optimizing targets defined by RTO is proposed. This strategy must comply with eventual unreachable targets and unmeasured disturbances. Consequently, its domain of attraction must be enlarged in order to circumvent infeasibility conditions. This is achieved by imposing terminal equality constraints solely on non-stable states, artificial equilibrium points and softening the bound-type constraints on states with suitable slack variables. Finally, a case study based on an unstable reactor is used to demonstrate the properties of the proposed strategy and the role of the terminal ingredients in the domain of attraction.