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Item type:Publication, Access status: with files , Multilinearization of polynomial models by linear state transformation(Elsevier, 2026-09-05); ; ; Many problems in engineering involve the analysis and model-based control of nonlinear systems. Often a tradeoff exists between the fidelity of the model and the computational complexity of analysis and design algorithms. Multilinear models offer significant advantages in this regard since they can be represented as tensors which enables efficient representation and computation, even in high-dimensional settings. This paper deals with the multilinearization of polynomial models through linear transformation. We are able to provide a comprehensive analysis for the case of two variables. For the higher dimensional case, we propose partial solutions which exploit our results for the two-dimensional case. We perform theoretical runtime analyses of the resulting algorithms which we also illustrate through numerical results.Publicationtype: Journal Article17 7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Tensor-based modeling framework for district heating pipes(Elsevier, 2026-04-25); ; ; ; District heating network simulation faces a fundamental computational challenge: traditional nonlinear models become intractable at large scales due to the curse of dimensionality, while linear models cannot accurately represent the nonlinear dynamics essential for district heating systems. Tensor-based methods have demonstrated effectiveness in modeling heating, ventilation, and air conditioning (HVAC) as well as local heating systems by providing a scalable compromise between accuracy and computational efficiency, yet their application to district heating networks is first described in this paper. This work applies multilinear time-invariant (MTI) modeling using a tensor-based framework for scalable representations of district heating networks.Tensor and multilinear functions efficiently represent the governing equations and their nonlinear relationships, especially the quadratic pressure-loss relationships defined by the Darcy-Weisbach equation and nonlinear friction factors across flow regimes without causing an exponential growth in model complexity. Binary variables model discontinuous transitions between laminar and turbulent flow, maintaining computational tractability while preserving physical accuracy. The tensor structure inherently avoids the curse of dimensionality that constrains conventional approaches by factorization. Benchmarking against established models on a small network shows minimal deviations alongside considerable memory reductions, demonstrating the potential of tensor-based methods for efficient simulation and optimization of large-scale district heating networks and supporting the integration of renewable energy sources and advanced control strategies essential for modern energy-efficient systems.Publicationtype: Journal Article16 14 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Convex Synthesis of Robust Distributed Controllers for the Optical Synchronization System at European XFELThis work proposes a single-step, LMI based synthesis method for the design of robust, distributed and fixed-order output-feedback controllers based on the sparsity invariance framework and the full block S-Procedure. The theoretic results are applied to the optical synchronization system at the European XFEL, which can be modeled as a distributed system of input-output connected, phase-locked oscillators. Whereas in recent work a decentralized controller structure for the nominal system was synthesized, this work continues to develop the synthesis method and adds robustness guarantees to the generated solution. We show simulation results motivated by the real application and demonstrate that, compared to the nominal decentralized solution, no additional conservatism is introduced by the robust solution, if the uncertainty approaches the nominal value.Publicationtype: Conference Paper41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Decentralized Output Feedback Control using Sparsity Invariance with Application to Synchronization at European XFEL(IEEE, 2021-12); ; ; ; In this work, we apply the recent framework of sparsity invariance to a large-scale facility, the European XFEL. With the sparsity invariance framework, the most general known class of convex approximations of distributed controller design problems is characterized. It is shown in previous work that this convex restriction can perform at least as well as all existing approximations for the possibly NP-hard problem of distributed controller design. The optical synchronization system at the European XFEL can be modeled as a distributed system with a tree or chain topology. Whereas in previous work based on the spatial invariance framework either static state feedback or high-order dynamic output feedback controller design is presented, we extend it in this work to static or fixed-order output feedback control and apply it to the system at hand. We show simulation results motivated by the real application and demonstrate that the convex approximation can outperform a local baseline tuning.Publicationtype: Conference Paper55 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Parameter identification of canalyzing boolean functions with ternary vectors for gene networksIn gene dynamics modeling, parameters of Boolean networks are identified from continuous data under various assumptions expressed by logical constraints. These constraints may restrict the dynamics of the network to the subclass of canalyzing functions, which are known to be appropriate for genetic networks. This paper introduces a high performance algorithm, which solves the parameter identification problem by so called Zhegalkin identification and exploits the restriction to canalyzing functions resulting in reduced calculation time. The canalyzing constraint is formulated in terms of orthogonal ternary vector lists-which are intrinsically used in a Branch-And-Cut algorithm obeying this constraint. The algorithm is applied to mRNA micro array data from mice under different contaminant conditions and good correspondence to a known apoptotic pathway can be shown.Publicationtype: Conference Paper16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Parameter identification of canalyzing and nested canalyzing boolean functions with ternary vectors for gene networksIn gene dynamics modeling, parameters of Boolean networks are identified from continuous data under various assumptions expressed by logical constraints. These constraints may restrict the dynamics of the network to the subclass of canalyzing or nested canalyzing functions, which are known to be appropriate for genetic networks. This paper introduces high performance algorithms, which solve the parameter identification problem by so called Zhegalkin identification and exploit the restriction to canalyzing or nested canalyzing functions resulting in reduced calculation time. The constraints are formulated in terms of orthogonal ternary vector lists, which offer an efficient representation for Boolean functions. The canalyzing constraints can be intrinsically incorporated in an existing Branch-and-Cut algorithm, which lead to a natural restriction of the search space and thus of the calculation time. For nested canalyzing constraints this is not possible. Instead, an identification algorithm based on enumeration is proposed. The algorithms are applied to mRNA micro array data from mice under different contaminant conditions and good correspondence to a known apoptotic pathway can be shown.Publicationtype: Conference Paper19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Plant modeling for observer-based control of the link stabilizing units at the European X-ray Free-Electron LaserThe European X-ray Free-Electron Laser will generate ultra short laser light pulses in the femto-second range to perform experiments with atomic scale resolution. A clock signal synchronizes all components and is distributed by a laser pulses train. These pulses are carried by an optical fiber which is spread through the facility and exposed to external disturbances which change the optical length of the fiber. It is of dire importance to keep this length stable because a change directly results in a timing error of the attached device. For this purpose Link Stabilizing Units are used. This paper shows the modeling of this unit, analyzes their main properties and points out the main control challenges.Publicationtype: Conference Paper53 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Hybrid multilinear modeling and applicationsTensor systems are a framework for modeling of multilinear hybrid systems with discrete and continuous valued signals. Two examples from building services engineering and multi-agent systems show applications of this framework. A tensor model of a heating system is derived and approximated by tensor decomposition methods first. Second, a tensor model of a multi-agent system with a structure already given in a decomposed form is reduced further by the same decomposition methods.Publicationtype: Conference Paper43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Modeling of the master laser oscillator phase noise for the European XFEL using fractional order systemsThe European X-ray Free-Electron Laser will generate high energy light pulses in the femto-second range. A clock signal, which synchronizes all components, is distributed via laser pulses. The accuracy of these laser pulses is crucial to achieve precise measurements which are needed to control the Free-Electron Laser. In order to reach the maximum performance, advanced model-based control approaches are used to compensate external influences. This paper shows the modeling of the Master Laser Oscillator by fractional order systems, which improve known approaches to system modeling by providing a higher accuracy.Publicationtype: Conference Paper22 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Tensor systems : multilinear modeling and applicationsTensor systems are a framework for modeling of multilinear hybrid systems with discrete and continuous valued signals. Two examples from building services engineering and multi-agent systems show applications of this framework. A tensor model of a heating system is derived and approximated by tensor decomposition methods first. Second, a tensor model of a multi-agent system with a structure already given in a decomposed form is reduced further by the same decomposition methods. The validity of these low rank approximations is shown for both examples.Publicationtype: Conference Paper388 441