A model predictive control framework with robust stability guarantees under unbounded disturbances

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Hauptverfasser: Köhler, Johannes, Zeilinger, Melanie N.
Format: Preprint
Veröffentlicht: 2022
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author Köhler, Johannes
Zeilinger, Melanie N.
author_facet Köhler, Johannes
Zeilinger, Melanie N.
contents To address feasibility issues in model predictive control (MPC), most implementations relax state constraints by using slack variables and adding a penalty to the cost. We propose an alternative strategy: relaxing the initial state constraint with a penalty. Compared to state-of-the-art soft constrained MPC formulations, the proposed formulation has two key features: (i) input-to-state stability and bounds on the cumulative constraint violation for unbounded disturbances; (ii) close-to-optimal performance under nominal operating conditions. The idea is initially presented for open-loop asymptotically stable nonlinear systems by designing the penalty as a Lyapunov function, but we also show how to relax this condition to: i) Lyapunov stable systems; ii) stabilizable systems; and iii) utilizing an implicit characterization of the Lyapunov function. In the special case of linear systems, the proposed MPC formulation reduces to a quadratic program, and the offline design and online computational complexity are only marginally increased compared to a nominal design. Numerical examples demonstrate benefits compared to state-of-the-art soft-constrained MPC formulations.
format Preprint
id arxiv_https___arxiv_org_abs_2207_10216
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle A model predictive control framework with robust stability guarantees under unbounded disturbances
Köhler, Johannes
Zeilinger, Melanie N.
Optimization and Control
Systems and Control
To address feasibility issues in model predictive control (MPC), most implementations relax state constraints by using slack variables and adding a penalty to the cost. We propose an alternative strategy: relaxing the initial state constraint with a penalty. Compared to state-of-the-art soft constrained MPC formulations, the proposed formulation has two key features: (i) input-to-state stability and bounds on the cumulative constraint violation for unbounded disturbances; (ii) close-to-optimal performance under nominal operating conditions. The idea is initially presented for open-loop asymptotically stable nonlinear systems by designing the penalty as a Lyapunov function, but we also show how to relax this condition to: i) Lyapunov stable systems; ii) stabilizable systems; and iii) utilizing an implicit characterization of the Lyapunov function. In the special case of linear systems, the proposed MPC formulation reduces to a quadratic program, and the offline design and online computational complexity are only marginally increased compared to a nominal design. Numerical examples demonstrate benefits compared to state-of-the-art soft-constrained MPC formulations.
title A model predictive control framework with robust stability guarantees under unbounded disturbances
topic Optimization and Control
Systems and Control
url https://arxiv.org/abs/2207.10216