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    Item type:Publication, Access status: without files ,
    Data-driven uncertainty propagation for stochastic predictive control of multi-energy systems
    (Elsevier, 2024-06-17)
    Özmeteler, M. Batu
    ;
    Bilgic, Deborah
    ;
    Pan, Guanru
    ;
    Koch, Alexander
    ;
    Faulwasser, Timm
    Stochastic predictive control schemes that account for epistemic and aleatoric uncertainties, i.e. lack of model knowledge and stochastic disturbances, are of major interest for multi-energy systems. However, there exists a trade-off between model complexity, computational effort, and accuracy of uncertainty quantification. This paper attempts to assess this trade-off by comparing a recently proposed approach combining Willems’ fundamental lemma with polynomial chaos expansion to a model-based scheme that first propagates uncertainty with PCE and then considers chance constraints in the optimization. The simulation results show that the data-driven scheme yields similar performance and computational efficiency compared to the model-based scheme, with the advantage of avoiding the construction of explicit models.
    Publicationtype: Journal Article
      18
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    Control of port-Hamiltonian systems with minimal energy supply
    (Elsevier, 2021-11-01)
    Schaller, Manuel
    ;
    Philipp, Friedrich
    ;
    Faulwasser, Timm
    ;
    Worthmann, Karl
    ;
    Maschke, Bernhard
    We investigate optimal control of linear port-Hamiltonian systems with control constraints, in which one aims to perform a state transition with minimal energy supply. Decomposing the state space into dissipative and non-dissipative (i.e. conservative) subspaces, we show that the set of reachable states is bounded w.r.t. the dissipative subspace. We prove that the optimal control problem exhibits the turnpike property with respect to the non-dissipative subspace, i.e., for varying initial conditions and time horizons optimal state trajectories evolve close to the conservative subspace most of the time. We analyze the corresponding steady-state optimization problem and prove that all optimal steady states lie in the non-dissipative subspace. We conclude this paper by illustrating these results by a numerical example from mechanics.
    Publicationtype: Journal Article
      6
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    Exact turnpike properties and economic NMPC
    (Elsevier, 2017-05-01)
    Faulwasser, Timm
    ;
    Bonvin, Dominique
    We discuss the design of sampled-data receding-horizon control schemes for continuous-time systems based on exact turnpike properties. We present sufficient convergence conditions that do not require any kind of terminal constraints or terminal penalties. We prove that, in the presence of state constraints, the existence of an exact turnpike implies recursive feasibility of the optimization. Furthermore, we show that turnpike exactness implies that the performance realized by the receding-horizon controller is equivalent to the infinite-horizon performance. We also state sufficient conditions for the exactness of turnpikes. Finally, we draw upon examples to illustrate our findings.
    Publicationtype: Journal Article
      10
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    Fast output sampling regulators with integral action
    (Elsevier, 2001)
    Werner, Herbert
    Fast output sampling controllers have been proposed as an alternative to observer-based state feedback control, and have been demonstrated to be useful for robust controller design. Here it is shown how integral action can be incorporated into the design. An LMI-based design procedure that has been proposed recently to trade fast decay of estimation errors against low noise-sensitivity, can be used at the same time to eliminate the estimation error resulting from an additional integrator loop. The proposed design method is illustrated by a practical application: a multivariable regulator for a turbogenerator is designed and experimental results are shown. © 2001 EUCA.
    Publicationtype: Journal Article
      16
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    Tracking and disturbance rejection for an uncertain system using fast output sampling
    (1999)
    Werner, Herbert
    It is shown how a recently proposed sampled-data, multi-rate output feedback controller can be designed to realise the effect of robust state feedback, so that when applied simultaneously to a family of linear plants, the closed-loop eigenvalues are retained. This is not possible when a Luenberger observer is used to realise state feedback. The multi-rate control law proposed here is useful because it allows to utilise previously developed LMI methods for robust state feedback design when the full state is not available for feedback. A practical design example is presented, and experimental results show that, using the same state feedback design, the multi-rate controller gives performance superior to that achieved with an observer.
    Publicationtype: Journal Article
      10
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    Partial model matching by static state feedback
    (Springer, 1996)
    Kučera, Vladimír
    ;
    Werner, Herbert
    Given a linear plant and a linear model, the partial model matching consists of compensating the plant so as to match several first Markov parameters of the model. A necessary and sufficient condition is given to solve the problem for single-input single-output systems using static state feedback. A simple design procedure is proposed which can incorporate the requirement of stability for the resulting system.
    Publicationtype: Journal Article
      17