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Błachowski B., Świercz A., Ostrowski M., Tauzowski P., Jankowski Ł., Computationally efficient optimal sensor placement,
DSA 2024, Dynamical Systems and Applications VI, 2024-06-26/06-28, Łódź (PL), pp.1-1, 2024Abstract: The topic of smart civil infrastructure has attracted significant attention. An important component of such structural systems is the network of sensors used to monitor the structure and deliver information about its current health status. The task of optimal sensor placement is not trivial due to the discrete, combinatorial nature of the problem. The brute force search is unfeasible for large structures, which calls for approximate and heuristic approaches. This problem has been investigated for several decades, beginning probably with the landmark 1978 paper of Shah [1]. A recent review can be found in [2].
The criteria typically used for assessing candidate placements are based either on Kammer’s Effective Independence (EFI) and the Fisher Information Matrix (FIM) [3], and quantify the amount of information provided by sensors, or on covariance matrices obtained within the Kalman filtering procedure used to quantify the uncertainty of the unknown response of interest being estimated [4]. However ingenious, most of the proposed procedures are computationally costly in large-scale problems.
This talk will discuss two optimal placement methods that have been recently developed with the objective of computational efficiency [5, 6]. One of them is based on Kalman filter covariance matrices and has—instead of typically quadratic—a linear complexity in the number of potential sensor locations. The other method uses the technique of convex relaxation to represent the problem in a computationally tractable continuous form and speed up the solution procedure even further. The presented application examples will use models of bridge structures.
[1] P.C. Shah, F.E. Udwadia, A methodology for optimal sensor locations for identification of dynamic systems, J. Appl. Mech. 45(1), 188–196 (1978)
[2] Y. Tan, L. Zhang, Computational methodologies for optimal sensor placement in structural health monitoring: A review, Struct. Health Monit. 19(4), 1287–1308 (2020)
[3] D.C. Kammer, Sensor placement for on-orbit modal identification and correlation of large space structures, J. Guid. Control Dyn. 14(2), 251–259 (1991)
[4] C. Zhang, Y.-L. Xu, Optimal multi-type sensor placement for response and excitation reconstruction, J. Sound Vib. 360, 112–128 (2016)
[5] B. Błachowski, A. Świercz A., M. Ostrowski, P. Tauzowski, P. Olaszek, L. Jankowski, Convex relaxation for efficient sensor layout optimization in large-scale structures subjected to moving loads, Comput.-Aided Civ. Inf. 35(10), 1085–1100 (2020)
[6] B. Błachowski, A. Świercz, P. Olaszek, Ł. Jankowski, Implementation of multi-type sensor placement strategy for large-scale engineering structures, 10th ECCOMAS Thematic Conference on Smart Structures and Materials (SMART 2023), July 3–5, 2023, Patras, Greece, pp. 498–506 (2023) Affiliations:
Błachowski B. | - | IPPT PAN | Świercz A. | - | IPPT PAN | Ostrowski M. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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2. |
Tauzowski P., Jarosik P., Żarski M.♦, Wójcik B.♦, Ostrowski M., Blachowski B.♦, Jankowski Ł., Computer vision-based inspections of civil infrastructure,
Modelling in Mechanics 2022, 2022-05-26/05-27, Rožnov pod Radhoštěm (CZ), pp.1-7, 2022Abstract: The uNET neural network architecture has shown very promising results when applied to semantic segmentation of biomedical images. The aim of this work is to check whether this architecture is equally applicable to semantic segmentation distinguishing the structural elements of railway viaducts. Artificial images generated by a computer graphics program rendering the 3D model of the viaduct in a photorealistic manner will be used as data sets. This approach produces a large number of
images that provide a solid training set for machine learning model. Keywords: Computer vision, deep learning, semantic segmentation Affiliations:
Tauzowski P. | - | IPPT PAN | Jarosik P. | - | IPPT PAN | Żarski M. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Wójcik B. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Ostrowski M. | - | IPPT PAN | Blachowski B. | - | other affiliation | Jankowski Ł. | - | IPPT PAN |
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Ostrowski M., Błachowski B., Mikułowski G., Jankowski Ł., Comparison of mode matching and bayesian approach for parametric identification of frames with bolted connections,
EACS 2022, 7th European Conference on Structural Control, 2022-07-10/07-13, Warszawa (PL), pp.86-86, 2022Abstract: Nowadays engineering studies require the use of the sophisticated finite element (FE) models consisting of hundreds if not thousands of degrees of freedom. However, using only such models does not allow for accurate reproduction of physical properties of real structures. To overcome this problem usually model updating (MU) techniques are employed. MU usually has one of two goals: 1) modification of some parameters of the model in order to minimize error between output of the FE model and experimental data obtained from the real system, and 2) identification of some properties of the real system using both experimental data and updated FE model. The former case relates to finding the model for performing simulations of the behaviour of the real system. In the later case MU can be applied in damage assessment process. Due to modelling uncertainties minimization of the error between measured and model output does not always provides the most accurate parametric identification. In this research unknown parameters describing rotational stiffness of bolted connections in a frame structure are estimated. Effectiveness of the two competitive model updating methods are compared. The first is based on modal sensitivities and minimizes error between numerical and experimental modal data. It requires matching of the numerical modes with the experimental ones, hence it is often called mode matching. The second is based on probabilistic Bayesian framework. In this approach maximum a posteriori (MAP) estimate of the unknown parameters is searched. It provides an augmented optimization allowing for model updating without mode matching. Moreover, this method is intended for parametric identification and explicitly includes the modelling errors into the problem formulation. In this study vibration modes are obtained from laboratory-scale frame with uncertain bolted connections. It is shown that assembly imperfections have significant influence on the mode shapes of the frame. The results also show that the two methods for model updating provide significantly different values of the identified stiffness parameters for the investigated bolted connections. Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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4. |
Ostrowski M., Błachowski B., Żarski M.♦, Wójcik B.♦, Tauzowski P., Jankowski Ł., Comparison of the accuracy of computer vision-based methods for estimation of structural displacements using synthetic video data,
EACS 2022, 7th European Conference on Structural Control, 2022-07-10/07-13, Warszawa (PL), pp.66-67, 2022Abstract: Despite significant advances in structural health monitoring (SHM), the design of contact sensor networks and their power supply for large-scale structures is still expensive and difficult. Due to the recent progress in computer vision (CV) it is possible to monitor structural components or even whole structures with the aid of digital cameras that allow to avoid the use of the contact sensors. However, CV-based measurements have a significantly lower accuracy than the techniques based on the contact sensors. Moreover, the amount of benchmark data available for development, testing and comparison of CV-based methods is limited. This problem has been partially overcome in recent years by the use of the physics-based graphical models (PBGM) in generation of synthetic but realistic video data. In this work, a comparison of two popular methods of CV-based object tracking applicable in SHM is discussed. PBGM-based videos used in this study are a part of The 2nd International Competition for Structural Health Monitoring'. Exact structural displacements are available due to the fact that PBGM-based video are generated using the structural model. Hence, calculation of the error metrics is straightforward and reliable. The PBGM-based videos show a spatial truss subjected to an unknown excitation. Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Żarski M. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Wójcik B. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Tauzowski P. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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5. |
Jankowski Ł., Popławski B., Ostrowski M., Jedlińska A., Mikułowski G., Błachowski B., Pisarski D., Wiszowaty R., Mróz A., Orłowska A., Hou J.♦, Holnicki-Szulc J., Semi-active mitigation of free and forced vibrations by means of truss-frame nodes,
CMM-SolMech 2022, 24th International Conference on Computer Methods in Mechanics; 42nd Solid Mechanics Conference, 2022-09-05/09-08, Świnoujście (PL), pp.1-2, 2022Abstract: This contribution reviews a recently proposed control strategy for mitigation of vibrations based on the Prestress-Accumulation Release (PAR) approach [1]. The control is executed by means of semi-actively controllable truss-frame nodes. Such nodes have an on/off ability to transfer bending moments: they are able to temporary switch their operational characteristics between the truss-like and the frame-like behaviors. The focus is not on local energy dissipation in the nodes treated as friction dampers, but rather on stimulating the global transfer of vibration energy to high-order modes. Such modes are high-frequency and thus highly dissipative by means of the standard mechanisms of material damping. The transfer is triggered by temporary switches to the truss-like state performed at the moments of a high local bending strain. A sudden removal of a kinematic constraint releases the locally accumulated strain energy into high-frequency and quickly damped vibrations.
The first formulation investigated global control laws [1]. Recent approaches generalized it to decen-tralized control with a local-only feedback, which was tested in damping of free vibrations [2] as well as forced vibrations [3]. Recently, a global formulation was proposed that aims at a targeted energy transfer between specific vibration modes [4], and attempts were made to go beyond skeletal struc-tures [5]. Numerical and experimental results will be presented to confirm the high effectiveness of the approach in mitigation of free, forced random and forced harmonic vibrations. Affiliations:
Jankowski Ł. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Ostrowski M. | - | IPPT PAN | Jedlińska A. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Pisarski D. | - | IPPT PAN | Wiszowaty R. | - | IPPT PAN | Mróz A. | - | IPPT PAN | Orłowska A. | - | IPPT PAN | Hou J. | - | Dalian University of Technology (CN) | Holnicki-Szulc J. | - | IPPT PAN |
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6. |
Ostrowski M., Błachowski B., Mikułowski G., Jankowski Ł., Identification of dynamic characteristics of uncertain bolted connections in a frame structure,
CMM-SolMech 2022, 24th International Conference on Computer Methods in Mechanics; 42nd Solid Mechanics Conference, 2022-09-05/09-08, Świnoujście (PL), pp.1-2, 2022Abstract: Parametric identification of structures and their components can be encountered in many engineering problems such as damage assessment or model updating for the control purposes. In the present study the attention is on two approaches to model updating. The first approach is the classical penalty func-tion that minimizes the square norm of the error between experimental and numerical modal data. The second one is a probabilistic Bayesian framework that maximizes the a posteriori probability density function of the unknown parameters based on the experimental data. The main difference between these two approaches is related to the fact that the penalty function methods requires matching of the numerical data with those obtained experimentally. The Bayesian approach is not vulnerable to this problem, but it requires more weighting parameters to be selected. An improper selection of these parameters leads to a worse identification accuracy. In this work, the two approaches are compared using data obtained from experiments on a laboratory-scale frame with highly uncertain bolted connec-tions. 17 uncertain stiffness parameters are to be identified: 16 of them correspond to the bolted con-nections and one to the Young modulus of the beams. 82 degrees of freedom are measured with the aid of 4 bidirectional accelerometers and roving sensor technique. Experimental modal data used for model updating contain nine mode shapes and the corresponding natural frequencies within the fre-quency range from 0 to 1 kHz. The research is divided into three steps: (1) model class selection, (2) assessment of the parameter identifiability and (3) updating of the selected model with the aid of both examined model updating methods.
Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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7. |
Ostrowski M., Błachowski B., Żarski M.♦, Wójcik B.♦, Tauzowski P., Jankowski Ł., Computer vision-based vibration measurement,
Modelling in Mechanics 2022, 2022-05-26/05-27, Rožnov pod Radhoštěm (CZ), pp.1-6, 2022Abstract: In the present study a benchmark test of selected methods of template matching-bated methods for computer vision-based object tracking is performed. The attention is paid to compare these methods in terms of estimation of nodal displacements in a flexible truss structure, aiming at assessment of their reliability in Structural Health Monitoring (SHM) applications. Thanks to the use of synthetic but realistic videos generated with the aid of physics-based graphics models (PBGM), exact displacement of tracked structural nodes are known. Therefore, reliable assessment of the accuracy of the examined methods is possible. Keywords: computer vision, structural health monitoring, physics-based graphics models (PBGM) Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Żarski M. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Wójcik B. | - | Institute of Theoretical and Applied Informatics, Polish Academy of Sciences (PL) | Tauzowski P. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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8. |
Ostrowski M., Błachowski B., Świercz A., Tauzowski P., Olaszek P.♦, Jankowski Ł., Efficient Method for Optimal Sensor Placement in Large-scale Structures,
CIMTEC 2022, 15th International Conference on Modern Materials and Technologies - 9th Forum on New Materials, 2022-06-25/06-29, Perugia (IT), pp.1, 2022Abstract: In practice, the broadly used finite element (FE) models can have very large number of degrees of freedom (DOFs). A small subset of DOFs representing sensor locations that provides an extremum of a selected objective function corresponding to a metric of the expected measurement accuracy is sought. Thus, optimal sensor placement is characterized by its complex combinatorial nature and tremendous computational effort required. With the aid of convex relaxation, the proposed approach allows one to transform the original combinatorial problem into its continuous counterpart, which requires smaller computational effort – by a few orders of magnitude than famous Effective Independence method. The effectiveness of the method has been demonstrated using an example of a FE model of an existing railway bridge. First, the FE model has been calibrated with measured responses of the bridge under the moving load of a passing train. Then, sensor layout has been obtained in such a way that it optimises the estimate of modal coordinates of the mode shapes participating most significantly in the measured structural response. The authors acknowledge the support of the National Science Centre, Poland (grant agreement 2018/31/B/ST8/03152). Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Świercz A. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Olaszek P. | - | Instytut Badawczy Dróg i Mostów (PL) | Jankowski Ł. | - | IPPT PAN |
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9. |
Jankowski Ł., Popławski B., Ostrowski M., Jedlińska A., Mikułowski G., Błachowski B., Pisarski D., Wiszowaty R., Mróz A., Holnicki-Szulc J., Semi-active damping of structural vibrations using controllable truss-frame nodes,
8WCSCM, 8th World Conference on Structural Control and Monitoring, 2022-06-05/06-08, Orlando, Florida (US), pp.1, 2022Abstract: This contribution reviews a recently proposed semi-active control approach based on the Prestress-Accumulation Release strategy, which aims at damping of structural vibrations by promoting vibration energy transfer from lower- into higher-order modes that have significant material damping. Unlike typical semi-active control, which focuses on local dissipation in actuators, the aim is to trigger natural global damping mechanisms. The actuators are controllable truss-frame nodes: lockable hinges that can change their mode of operation from a frame node (locked hinge) into truss node (free rotation). Sudden removal of such a kinematic constraint releases the accumulated bending energy into high-frequency quickly damped local vibrations. Two formulations are reviewed: decentralized with local-only feedback, and global, which aims at a targeted energy transfer between specific modes. Experimental results confirm the effectiveness using free, forced harmonic and random vibrations. Affiliations:
Jankowski Ł. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Ostrowski M. | - | IPPT PAN | Jedlińska A. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Pisarski D. | - | IPPT PAN | Wiszowaty R. | - | IPPT PAN | Mróz A. | - | IPPT PAN | Holnicki-Szulc J. | - | IPPT PAN |
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10. |
Ostrowski M., Błachowski B., Mikułowski G., Jankowski Ł., Parametric identification of uncertain bolted connections with Bayesian approach,
LSCE, XXVII Conference of Lightweight Structures in Civil Engineering, 2021-12-02/12-03, Łódź (PL), pp.93-96, 2021Abstract: The paper presents the parametric identification of structural connections characterised by highly uncertain stiffness. Such uncertainties often appear in structural bolted connections. One of the common problems in parametric identification with the use of modal data is the problem of the mode matching. In this work the model updating method based on the Bayesian approach was used to identify the unknown parameters. Due to the probabilistic framework it allows to avoid the problem of the mode matching. A laboratory-scale frame structure is considered in this research, however this structure contains bolted connections common also in large-scale light-weight structures. The problem of parametric identification has been decomposed into the following tasks: (a) selection of the finite element model, (b) evaluation of the identifiability of the parameters, and (c) updating the finite element model with the use of available measurement data. Keywords: Bayesian approach, mode matching, system identification, model updating, bolted connections Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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11. |
Ostrowski M., Błachowski B., Mikułowski G., Jankowski Ł., Bayesian approach for efficient identification of highly uncertain structural parameters,
WEO 2021, 2nd Workshop on Engineering Optimization, 2021-10-07/10-08, Warszawa (PL), pp.39-43, 2021 | |
12. |
Ostrowski M., Świercz A., Błachowski B., Tauzowski P., Jankowski Ł., Optimization of Sensor Placement Using Continuous Approaches,
WEO2019, Workshop on Engineering Optimization 2019, 2019-11-04/11-04, Warszawa (PL), pp.22-23, 2019Abstract: The present study provides a comprehensive framework for sensor layout optimization aiming at accurate estimation of the modal coordinates coming from the structural response. The proposed procedure consists of two steps briefly described below. The first step is a selection of vibrational modes taking part in the motion of structures during their normal operation – in this case subjected to traveling load. Among these structures there are various types of bridges especially railway bridges. In the case of present study structural responses are obtained from rigorous finite element (FE) model of the bridge. The FE model is calibrated with measured response of real bridge located in Huta Zawadzka. The calibration process is based on the displacement signals of the bridge under the traveling load. In the second step modes of interest are selected and a set of candidate sensor locations is proposed. It is a subset of all degrees of freedom (DOFs) of the FE model from which several locations are chosen as best possible locations for the displacement sensors. The above sensor placement problem is a combinatorial task. Many methods for solving such problems have been developed previously, but in the case of large scale structures they require tremendous computational effort. To reduce this effort the so-called convex relaxation is incorporated into optimization process. The technique consists in reformulation of combinatorial problem into continuous convex one. Then, the convex relaxation is achieved by introducing the so-called sensor density function, which assigns a certain metric for individual candidate sensor location. Next, the value of this function is optimized in such a way that it maximize determinant of the Fisher Information Matrix. It has been shown that above algorithm is very effective and is distributing a number of sensors in several iterations only. Finally, it is worth noting that presented method can be used to distribute sensors for structural health monitoring. Moreover, it can be also applied in modal control strategies in vibration suppression. Affiliations:
Ostrowski M. | - | IPPT PAN | Świercz A. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Tauzowski P. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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13. |
Ostrowski M., Błachowski B., Jankowski Ł., Pisarski D., Półaktywne sterowanie drganiami konstrukcji przy użyciu dynamicznie aktywowanych połączeń,
SAM2019, XVIII Szkoła Analizy Modalnej, 2019-06-06/06-07, Kraków (PL), pp.1, 2019Abstract: W ostatnim czasie wiele prac naukowych poświęcono problemom półaktywnego sterowania drganiami układów mechanicznych. Większość tych prac jednak dotyczy zagadnienia tłumienia drgań, natomiast znacznie mniej z nich obejmuje strategie sterowania na potrzeby odzyskiwania energii z drgających układów. Celem niniejszej pracy jest opracowanie strategii półaktywnego sterowania drganiami, mającej za zadanie przenosić energię drgań wzbudzanych losowo do jednej wybranej postaci drgań własnych. Sterowanie takie realizowane jest przy pomocy dynamicznie rozłączanych węzłów konstrukcyjnych. Węzły w zależności od sygnału sterowania mogą być blokowane w celu przenoszenia momentu zginającego pomiędzy łączonym członami konstrukcji lub odblokowywane, aby pracować jak połączenie przegubowe. Prowadzone badania podstawowe mają wiele potencjalnych zastosowań. Wraz ze zmianą postaci drgań, istnieje możliwość zmiany amplitudy w miejscach, w których zainstalowany jest tłumik lub urządzenie odzyskujące energię (ang. energy-harvester). Możliwe jest również szybkie przeniesienie energii mechanicznej do postaci drgań, która nie zakłóca funkcjonalności konstrukcji lub nie powoduje jej uszkodzenia bądź zmęczenia. W porównaniu do sterowania aktywnego stosowanie sterowania półaktywnego pozwala obniżyć koszty układu, dodatkowo nie powodując destabilizacji konstrukcji [1]. Sterowanie takie może z powodzeniem znaleźć zastosowanie w konstrukcjach o wielu stopniach swobody [2]. Strategia półaktywnego sterowania z użyciem blokowalnych węzłów pierwotnie została opracowana w celu przeniesienia energii drgań do wyższych postaci własnych w celu skutecznej ich redukcji przez tłumienie materiałowe [3]. W niniejszej pracy zaprezentowany zostanie model matematyczny transferu energii oraz oparte na nim prawo sterowania. Dodatkowo przedstawiony zostanie przykład numeryczny pokazujący, że transfer energii mechanicznej jest możliwy nawet wtedy, gdy mierzone są tylko pierwsze – podstawowe – postacie drgań własnych. Prowadzone badania zostały wsparte przez Narodowe Centrum Nauki w ramach projektu Re-Conf (DEC-2017/25/B/ST8/01800). Keywords: sterowanie półaktywne, analiza modalna, blokowane węzły Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Pisarski D. | - | IPPT PAN |
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14. |
Ostrowski M., Błachowski B., Jankowski Ł., Pisarski D., Semi-Active Control of Mechanical Energy Transfer Between Vibrational Modes,
SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P136, pp.408-409, 2018Abstract: The vibration attenuation problem has been solved using many different methods, some of which involve the use of advanced control algorithms. The topic of harvesting the energy of structural vibrations is less explored. For that reason, this contribution studies the problem of conversion of mechanical energy of vibrations. The paper presents a method of semi-active control, which is applied to dynamically transfer the vibration energy into a selected vibration mode. The target mode is selected in such a way that the amount of energy that can be recovered during the vibration process is maximized. In other words, switching between two modes is not intended to dissipate the energy of vibrations, but rather to maximize the energy-harvesting potential of the overall system. The concept will be illustrated using an example of a simple frame structure, in which semi-actively controlled lockable joints modify the modal properties of the structure. Keywords: semi-active control, lockable joints, energy-harvesting Affiliations:
Ostrowski M. | - | IPPT PAN | Błachowski B. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Pisarski D. | - | IPPT PAN |
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