An economic MPC formulation with offset-free asymptotic performance. Issue 18 (2018)

• Record Type: Journal Article
• Authors: Pannocchia, Gabriele
• Is Part Of: IFAC-PapersOnLine. Volume 51:Issue 18(2018)
• Page Start: 393
• Page End: 398
• Publication Date: 2018
• Subjects: Economic MPC -- RTO -- Offset-free Control -- Modifier-Adaptation -- Uncertainties; Automatic control -- Periodicals; 629.805
• DOI: 10.1016/j.ifacol.2018.09.332
• Languages: English
• ISSNs: 2405-8963

Abstract

Abstract: This paper proposes a novel formulation of economic MPC for nonlinear discrete-time systems that is able to drive the closed-loop system to the (unknown) optimal equilibrium, despite the presence of plant/model mismatch. The proposed algorithm takes advantage of: (i) an augmented system model which includes integrating disturbance states as commonly used in offset-free tracking MPC; (ii) a modifier-adaptation strategy to correct the asymptotic equilibrium reached by the closed-loop system. It is shown that, whenever convergence occurs, the reached equilibrium is the true optimal one achievable by the plant. An example of a CSTR is used to show the superior performance with respect to conventional economic MPC and a previously proposed offset-free MPC still based on a tracking cost. The implementation of this offset-free economic MPC requires knowledge of plant input-output steady-state map gradient, which is generally not available. To this aim a simple linear identification procedure is explored numerically for the CSTR example, showing that convergence to a neighborhood of the optimal equilibrium is possible.