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Faraj R., Popławski B., Hinc K.♦, Preliminary study on modelling and optimization of the rescue cushion system,
ISMA2020 / USD2020, International Conference on Noise and Vibration Engineering / International Conference on Uncertainty in Structural Dynamics, 2020-09-07/09-09, Leuven (BE), pp.2675-2684, 2020 Abstract: The paper is aimed at modelling and optimization of a rescue cushion system, which is a device used by fire brigades for evacuation of people from buildings. The goal of the study is an improvement of the system response under various operational conditions. For faster and cheaper analysis of the system performance and further development of the complex structure of the rescue cushion system, a dedicated dynamical model is elaborated. Implemented numerical model is further applied for the parametric study in order to evaluate the influence of selected airbag parameters on the effectiveness of impact mitigation process and to determine possible improvements of the actual system design. In particular, adaptation of the rescue cushion to the mass of landing person, as well as to the initial velocity, is analyzed. Simultaneously, the necessity of meeting all the functional and operational requirements is taken into account. The most promising directions of further research are indicated. Affiliations:
Faraj R. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Hinc K. | - | other affiliation |
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Mikułowski G., Popławski B., Jankowski Ł., An experimental investigation of the prestress accumulation release strategy for local mitigation of structural vibrations,
SMART 2019, 9th ECCOMAS Thematic Conference on Smart Structures and Materials, 2019-07-08/07-11, Paris (FR), pp.323-332, 2019 Abstract: This contribution presents an experimental analysis of the control system configuration for a semi-active frame structure. The structure is equipped with a system that implements a Prestress Accumulation Release strategy for mitigation of vibration. A proper distribution of the sensors for monitoring the actual state of the structure is the key factor that determines the overall effectiveness of the applied strategy. The results and findings presented here reveal a set of basic rules dedicated to solving this crucial issue. Keywords: Prestress Accumulation Release, Vibration control, Sensor placement, Semi-active structures, Piezoelectric actuation Affiliations:
Mikułowski G. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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Popławski B., Mikułowski G., Jankowski Ł., Semi-active decentralized mitigation of randomly excited vibrations in 2D frame structures,
SMART 2019, 9th ECCOMAS Thematic Conference on Smart Structures and Materials, 2019-07-08/07-11, Paris (FR), pp.357-363, 2019 Abstract: Semi-active control systems are investigated for more than 40 years, and despite the great progress in this research area, they are still considered to be a complex topic in both theoretical and technical terms. However, their advantages ensure that these control systems remain an extremely attractive subject of scientific and technological development.
In this contribution, we present a semi-active strategy for mitigation of vibration, which utilizes an energy management approach called Prestress-Accumulation Release and is based on controllable activation and removal of selected structural constraints. Here, it is implemented by means of controllable structural nodes of a specific design that allow the transmission of moments between adjacent structural elements to be controlled in an on/off manner. The developed control strategy turned out to be very effective in damping of free structural vibrations of planar frame structures. Extension of the research to other types of vibrations has shown that the proposed control algorithm is versatile and stays efficient in a range of applications and different configurations of the investigated structures. This work is focused on mitigation of vibrations excited by a randomly generated force load.
Decentralization, understood here as controlling the employed actuators based on locally measured structural response, results in a decisive reduction of the complexity of the data acquisition and control systems, which is crucial for actual implementations in real structures, and which facilitates an ad hoc reconfiguration and expansion of the control system if necessary. It also provides the possibility of considering selected structural elements as separate energy dissipative devices, which in our approach act effectively as vibration dampers. This feature, provided by the decentralization, enables to take the advantage of two complementary, interrelated mechanisms of material damping: global dissipation of vibration energy by the PAR and local dissipation in single involved elements.
Numerical and experimental analyses indicate a high degree of effectiveness in alleviation of the amplitude of vibrations induced by a random transient force excitation. The proposed control strategy can be thus utilized not only in the case of momentary impulsive loads that result in predominantly free vibrations, but also in the case of transient random force excitation. It significantly extends the range of possible modes of operation of a structure equipped with the proposed damping system. Keywords: Semi-active damping, Vibration damping, Random vibration, Forced vibration Affiliations:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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Mikułowski G., Popławski B., Wiszowaty R., Mróz A.♦, Jankowski Ł., An investigation on a semi-active damping of forced structural vibrations by means of controllable structural nodes,
ISMA 2018 / USD 2018, International Conference on Noise and Vibration Engineering / International Conference on Uncertainty in Structural Dynamics, 2018-09-17/09-19, Leuven (BE), pp.189-201, 2018 Abstract: Vibration mitigation in space structures creates a unique class of a technical problem where resistant for outgassing and non-fluidic solutions are preferable. Additionaly, a vibration induced by time-varying excitations needs to be effectively reduced. The vibration mitigation task is speciffically difficult in the case of light, slender and inherently flexible structures of various types, such as supporting structures, deployable structures, modular structures or wide-span skeletal roofing structures. This study presents a concept of a vibration attenuation method based on semi-active joints and dedicated to frame structures under forced vibration excitation. The presented investigation contains an analysis of the problem of the optimal control of a structure fitted with semi-active structural members. Furthermore, an adequate model of the semi-active joints is developed and a numerical example is presented. Finally, the research provides an experimental verification of the developed control algorithms, which is conducted on a test stand in a laboratory environment. Affiliations:
Mikułowski G. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Wiszowaty R. | - | IPPT PAN | Mróz A. | - | other affiliation | Jankowski Ł. | - | IPPT PAN |
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Popławski B., Mikułowski G., Suwała G., Jankowski Ł., Optimization of actuator placement for vibration damping in the Prestress-Accumulation release control approach,
WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.818-827, 2018 Abstract: This contribution proposes a quantitative criterion for optimization of actuator placement for the Prestress–Accumulation Release (PAR) strategy of mitigation of vibrations. The PAR strategy is a semi-active control approach that relies on controlled redistribution of modal energy into high-frequency high-order modes, where it is effectively dissipated by means of the natural mechanisms of material damping. The energy transfer is achieved by a controlled temporary removal of selected structural constraints. An example is a short-time decoupling of rotational degrees of freedom in a frame node, so that the bending moments are no longer transferred between the involved beams. If it such a decoupling is performed at the maximum of the shear/bending strain energy of adjacent beams, it results in an almost instantaneous energy release into high-frequency local vibrations and quick dissipation of energy. We propose and test a quantitative criterion for placement of such actuators. The criterion is based on local modal strain energy that can be released into high-order modes. The numerical time complexity is linear with respect to the number of actuators, which facilitates quick selection of placements in large structures. Keywords: semi-active control, damping of vibrations, actuator placement, smart structures, Prestress-Accumulation Release (PAR) Affiliations:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Suwała G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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Popławski B., Mikułowski G., Mróz A.♦, Jankowski Ł., Decentralized algorithm for semi-active damping of forced vibrations using controllable truss-frame nodes,
WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.582-590, 2018 Abstract: Semi-active systems for mitigation of vibrations proved to be effective in many applications. Their prominent advantage is that they combine strong points of passive and active damping systems. Proper design can ensure their reliability, which is what passive systems are praised for. A high effectiveness in vibration damping links them with active systems. At the same time they do not have many deficiencies of active systems. They are adaptive, so they can stay effective in different environmental conditions, which is the factor that eliminates passive systems from many implementations. Their mass and energy consumption is very low, and the controlled structure can stay in the safe configuration even in case of power supply failure, which puts them in contrast to many active systems. The mentioned attributes make them a good choice for many structures subjected to vibrations, especially when there is a strong emphasis on maximization of the efficiency/mass ratio of the damping system.
This contribution presents a decentralized closed-loop control strategy and applies it in a frame structure equipped with controllable truss-frame nodes. Such nodes can be switched between frame-like and truss-like states in a controllable manner. In the frame-like state the node transmits all forces and moments, while in the truss-like state only axial and shearing forces are transmitted. These nodes allow for structural reconfiguration, which can be utilized by semi-active control strategies for the purpose of vibration damping. The implemented control algorithm applies the Prestress-Accumulation Release (PAR) strategy based on the transmission of the accumulated potential energy to high modes of vibration, which are highly dissipative. Strain measurements are conducted locally on selected elements. A similar strategy proved its effectiveness in mitigation of free structural vibrations. This research studies the concept of its application to mitigation of forced structural vibrations, caused by variable external conditions. Keywords: Semi-active damping, Truss-frame nodes, Prestress-Accumulation Release (PAR), Decentralized control Affiliations:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Mróz A. | - | other affiliation | Jankowski Ł. | - | IPPT PAN |
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Popławski B., Mikułowski G., Mróz A., Sekuła K.♦, Jankowski Ł., A decentralized strategy of structural reconfiguration in mitigation of vibrations,
Procedia Engineering, ISSN: 1877-7058, DOI: 10.1016/j.proeng.2017.09.363, Vol.199, pp.1683-1688, 2017 Abstract: This contribution proposes a decentralized closed-loop control algorithm for semi-active mitigation of free vibrations in frame structures. The control uses dedicated dissipative devices, which consist of two controllable structural nodes placed pairwise in both ends of selected structural beams. The nodes are capable of a controlled transition between the standard frame mode of operation (full moment-bearing ability) and the truss mode in which they do not bear any moments and constitute in fact structural hinges. Synchronous switching is equivalent to reconfiguration of the global structure by (dis)allowing the involved beams to transmit moments and to accumulate vibration energy in the form of their bending strain. Upon switching to the truss mode, the accumulated energy is released into high-frequency local vibrations, which undergo quick dissipation by standard mechanisms of material damping. The approach is illustrated in a numerical example and verified in a preliminary experimental test. Keywords: Mitigation of vibrations, Semi-active control, Decentralized control, Structural reconfiguration Affiliations:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Mróz A. | - | IPPT PAN | Sekuła K. | - | other affiliation | Jankowski Ł. | - | IPPT PAN |
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Popławski B., Mikułowski G., Mróz A., Jankowski Ł., Decentralized damping of vibrations in 2D frame structures using controllable nodes,
SMART 2017, 8th Conference on Smart Structures and Materials, 2017-06-05/06-08, Madrid (ES), pp.94-103, 2017 Abstract: Extensive research efforts have been recently devoted to semi-active structural control with its paradigms of smart self-adaptivity and low consumption of energy, which is used for local adaptation rather than to generate external control forces. Considered application areas include adaptive landing gears, seismic isolation systems, vehicle-track/span systems, power train electro-mechanical systems, damping of flexible space structures, vehicle crashworthiness, arctic engineering, wind turbines, etc. A part of the research concerns semi-active management of strain energy for damping of structural vibrations. Early works considered truss structures with stiffness-switched bars. They later evolved into either standalone one degree of freedom stiffness-switched dampers and isolators or investigations in triggering modal energy transfer to highly-damped high-order modes. The latter researches seem all to study the fundamental vibration mode of a cantilever beam with two detachable layers and differ mainly in the actuator technologies; the main idea is to employ actuators for a quick release of the vibration-related strain energy. This research extends the problem to general 2D frames. Controllable truss-frame nodes are incorporated into the structure. Thanks to their controllable ability to transmit moments, they allow for a quick transition between truss and frame modes. We propose a new, decentralized, closed-loop control strategy based on local energy measures. Vibration damping is more effective than in the previously studied control scheme based on a global energy measure, especially for higher vibration modes. Mitigation of vibrations will be presented in representative numerical examples, including a comparison to the global energy-based control strategy. Finally, results of experimental study, conducted on a structure analogous to the one from numerical simulations, will be demonstrated. Keywords: Vibration damping, Smart structures, Semi-active control, PAR strategy, Decentralized damping strategy Affiliations:
Popławski B. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Mróz A. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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Faraj R., Popławski B., Suwała G., Jankowski Ł., Holnicki-Szulc J., Mitigation of dynamic response in frame structures by means of smart joints,
SMART 2017, 8th Conference on Smart Structures and Materials, 2017-06-05/06-08, Madrid (ES), pp.138-144, 2017 Abstract: This paper discusses passive and semi-active techniques of structural control by means of smart joints, and then it proposes a specific smart joints system for frame structures and tests its capability in mitigation of free vibrations. Basically, the proposed solution modifies frame beams by addition of truss-type hinges, and its effectiveness relies on the softening effect that occurs in compression due to geometric nonlinearities and which triggers the highly-damped high-frequency response modes of the structure. First, the finite element (FE) model of the specific frame structure with geometrical nonlinearities is derived, and the proposed passive joints are described and incorporated into the model. Then, their principle of operation and effectiveness is examined numerically for the first two natural modes of vibrations with various initial displacement amplitudes. An objective function is proposed to assess joints placement, based on the efficiency in mitigation of the excited vibrations. Keywords: Vibration Damping, Structure Response, Smart Structure, Structural Control Affiliations:
Faraj R. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Suwała G. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN | Holnicki-Szulc J. | - | IPPT PAN |
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Popławski B., Graczykowski C., Jankowski Ł., Controllable Truss-Frame Nodes in Semi-Active Damping of Vibrations,
Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.101.89, Vol.101, pp.89-94, 2017 Abstract: In recent years, vibration damping strategies based on semi-active management of strain energy have attracted a large interest and were proven highly effective. However, most of published research considers simple one degree of freedom systems or study the same basic example (the first vibration mode of a cantilever beam) with the same control strategy. This contribution focuses on truss-frame nodes with controllable moment-bearing ability. It proposes and tests an approach that allows the control strategy to be extended to more complex structures and vibration patterns. Keywords: adaptive impact absorption, smart structures, semi-active control, safety engineering Affiliations:
Popławski B. | - | IPPT PAN | Graczykowski C. | - | IPPT PAN | Jankowski Ł. | - | IPPT PAN |
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11. |
Jankowski Ł., Graczykowski C., Pawłowski P., Mikułowski G., Ostrowski M., Popławski B., Faraj R., Suwała G., Holnicki-Szulc J., Adaptive Self-Protection against Shock and Vibration,
Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.101.133, Vol.101, pp.133-142, 2017 Abstract: This contribution reviews the challenges in adaptive self-protection of structures. A proper semi-active control strategy can significantly increase structural ability to absorb impact-type loads and damp the resulting vibrations. Discussed systems constitute a new class of smart structures capable of a real-time identification of loads and vibration patterns, followed by a low-cost optimum absorption of the energy by structural adaptation. Given the always surging quest for safety, such systems have a great potential for practical applications (in landing gears, road barriers, space structures, etc.). Compared to passive systems, their better performance can be attributed to the paradigm of self-adaptivity, which is ubiquitous in nature, but still sparsely applied in structural engineering. Being in the early stages of development, their ultimate success depends on a concerted effort in facing a number of challenges. This contribution discusses some of the important problems, including these of a conceptual, technological, methodological and software engineering nature. Keywords: adaptive impact absorption, smart structures, semi-active control, safety engineering Affiliations:
Jankowski Ł. | - | IPPT PAN | Graczykowski C. | - | IPPT PAN | Pawłowski P. | - | IPPT PAN | Mikułowski G. | - | IPPT PAN | Ostrowski M. | - | IPPT PAN | Popławski B. | - | IPPT PAN | Faraj R. | - | IPPT PAN | Suwała G. | - | IPPT PAN | Holnicki-Szulc J. | - | IPPT PAN |
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