On Gain Design in Virtual Output Feedback for Model Updating

Ulriksen, Martin Dalgaard; Bernal, Dionisio

doi:10.1007/978-981-13-8331-1_26

Cited by 9 publications

(3 citation statements)

References 10 publications

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“…The N gains to be used in the updating can be designed using different approaches [18,21,22,23]. Here, we employ a gain design aiming to decrease the condition number of the Jacobian matrix in (1).…”

Section: Model Updating Formulation and Gain Designmentioning

confidence: 99%

Closed-loop updating of wind turbine models using blade pitch excitation

Schwarz-Wolf¹,

Ulriksen²,

Augustyn³

et al. 2021

Preprint

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Structural monitoring of wind turbines often involves the use of a numerical model, which must be regularly updated to yield an adequate representation of the governing dynamics. The model updating can be cast as an inverse problem, in which selected model parameters are estimated by minimizing the discrepancy between experimental target poles and model-predicted ones. An issue that may prevail in this setting is that the problem will be ill-posed, because the number of model parameters to be updated exceeds the number of target poles. The noted issue can be remedied by a virtual implementation of output feedback, which allows for computation of multiple closed-loop (CL) eigenstructures through non-linear transformations of the open-loop transfer matrix. The present paper offers an application study, in which virtual output feedback is used for updating numerical wind turbine models based on CL system poles. In particular, we explore the feasibility of employing the excitation stemming from the blade pitch control system as the input in the open-loop input-output realization required in the virtual output feedback. The methodological concept is outlined, and subsequently the applicability of the procedure is tested numerically in the context of simulations with a finite element model of a parked wind turbine. The preliminary findings suggest that procedures for customizing the pitch excitation to yield sufficient system excitation are required for the CL model updating to be feasible.

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Section: Model Updating Formulation and Gain Designmentioning

confidence: 99%

Closed-loop updating of wind turbine models using blade pitch excitation

Schwarz-Wolf¹,

Ulriksen²,

Augustyn³

et al. 2021

Preprint

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“…Another design target could be to minimize the uncertainties associated with the estimation of assigned closed‐loop poles, which has been suggested by Adamson et al 21 . In the context of model updating, control strategies have been used to mitigate the issues of ill‐posedness and/or ill‐conditionedness—which often arise in the open‐loop parameter estimation 22 —by introducing auxiliary equations through multiple closed‐loop eigenstructures 23,24 …”

Section: Introductionmentioning

confidence: 99%

Closed‐loop experimental testing framework for structural control applications

Pedersen

Ulriksen

2021

Struct Control Health Monit

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Within civil engineering, the inclusion of control strategies is confined to limited application areas due to the practical overhead and an alleged conservatism. This paper presents a simple yet flexible framework for experimental testing of closed‐loop structural systems. Compared to alternative existing solutions, the proposed framework requires limited programming knowledge, which heavily simplifies the implementation for the operator and thus reduces the associated practical overhead. The feasibility of the framework is demonstrated through two experimental case studies in which control strategies are used to, respectively, design and implement a hybrid tuned mass damper (TMD) and conduct closed‐loop model updating. The case studies exemplify the diversity of control applications within civil engineering, and it is noted that while hybrid TMDs are used in the civil engineering industry, limited experimental application studies exist on closed‐loop model updating of structural systems. It is concluded that the presented framework can be applied to cover a variety of structural control applications within civil engineering and the successful implementation of the framework in the two case studies highlights the benefits of feedback control within these applications.

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“…The second option for improving damage detectability, namely, enhancing the sensitivity to damage, can be addressed via structural control schemes. Specifically, closed-loop (CL) systems can be designed by using an eigenstructure assignment scheme, which allows for assignment of eigenvalues and/or eigenvectors (and hence mode shapes) such that these eigencharacteristics exhibit higher sensitivity to damage than the open-loop (OL) counterparts [25,26,27]. The concept was introduced to the field of structural damage detection by Ray and Tian [25], who used an eigenstructure assignment scheme to design a feedback controller to enhance the sensitivity to damage of a subset of eigenvalues.…”

Section: Introductionmentioning

confidence: 99%

Damage detection under temperature variability using closed-loop mode shapes

Qadri¹,

Kristensen²,

Ulriksen³

2020

Preprint

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The dynamic characteristics of any structural system depend on the temperature. This poses a challenge in vibration-based damage detection, as temperature variability can mask damage-induced shifts in the vibration features. Different means for resolving the issue have been put forth, and two general method types can be distinguished; (i) those mitigating the effect of temperature variability on the features and (ii) those increasing the sensitivity to damage of the features. The present paper explores the use of features composed of closed-loop (CL) mode shapes, which combine attributes from both method groups by offering adequate sensitivity to damage and robustness to temperature variability. The CL mode shapes are designed using an eigenstructure assignment scheme formulated as a bi-objective optimization problem. The first objective is the reciprocal of the spectral norm of the CL mode shape Jacobian matrix, which is thus to be minimized to maximize the sensitivity to damage. The second objective, whose implementation hinges on the assumptions that temperature variability induces spatially uniform stiffness changes and that homogeneous sensing is employed, is a measure of how much the damping in each of the assigned CL modes deviates from a classical distribution. Since classically damped mode shapes obtained using homogeneous sensing are invariant under spatially uniform stiffness changes, the latter objective is minimized to promote robustness to temperature variability. The designed CL mode shape features can be used in any damage detection method, but in the paper we restrict the use to outlier analysis and assess the merit of the proposed scheme in the context of numerical examples. The damage detection results are compared to findings obtained using cointegration (a well-established method for mitigating the effect of temperature variability), and it is seen how the proposed scheme outperforms the cointegration-based method.

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On Gain Design in Virtual Output Feedback for Model Updating

Cited by 9 publications

References 10 publications

Closed-loop updating of wind turbine models using blade pitch excitation

Closed-loop updating of wind turbine models using blade pitch excitation

Closed‐loop experimental testing framework for structural control applications

Damage detection under temperature variability using closed-loop mode shapes

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