检索结果-内蒙古大学图书馆

11th European Workshop on Structural Health Monitoring, EWSHM 2024

作者： Varouxis, Theodoros Dertimanis, Vasilis Abdallah, Imad Chatzi, Eleni Pakrashi, Vikram Malekjafarian, Abdollah Structural Dynamics and Assessment Laboratory School of Civil Engineering University College Dublin Dublin Ireland Department of Civil Environmental and Geomatic Engineering ETH Zurich Zurich Switzerland UCD Centre for Mechanics Dynamical Systems and Risk Laboratory School of Mechanical and Materials Engineering University College Dublin Dublin Ireland

Reducing the operation and maintenance (O&M) costs of wind farms can foster adoption of environmentally sustainable and cost-effective energy sources. O&M costs in Wind Turbines can account up to 35% of the turbine's total levelized cost per KWh, with a large portion attributed to that for wind turbine blades (WTB). In the present study, an experimental campaign for fatigue damage progression monitoring is presented. After subjecting the WTB to cyclic loading, an artificial transverse crack was introduced in the trailing edge (TE).The dynamic response of the blade to three different excitation schemes - white noise, white noise with the inclusion of a fundamental sinusoidal component and a frequency sweep- is obtained via the use of accelerometers, strain gauges and a real-time deflection monitoring system. These tests yielded generated 4 different health states, the initial healthy and 3 damaged states. The progressive damage is presented using frequency response functions (FRFs),while a simple deep-learning damage detection framework is developed. A conventional autoencoder (AE) is trained using the Frequency Response Functions (FRFs) corresponding to the blade's healthy state;then, an unsupervised damage detection algorithm is formulated using the AE. © 2024 11th European Workshop on Structural Health Monitoring, EWSHM 2024. All rights reserved.

关键词： Fatigue damage

来源：评论

学校读者我要写书评

暂无评论

Adaptive Linear Control of a Cartpole Using Minimum Spiking Neurons Trained with Prescribed Error Sensitivity

Adaptive Linear Control of a Cartpole Using Minimum Spiking ...

引用

MECHATRONIKA International Symposium

作者： Shreyan Banerjee Aasifa Rounak Vikram Pakrashi School of Mechanical and Materials Engineering UCD Centre for Mechanics Dynamical Systems and Risk Laboratory University College Dublin Dublin Ireland

ISBN: (数字)9798350394900

ISBN: (纸本)9798350394917

In the search for highly parallel, power-efficient, and scalable chips for control applications, neuromorphic architecture has emerged as a promising candidate. Neuromorphic computing promises to address some of the the von Neumannian computing challenges, and computes using spiking neurons with adjustable synaptic delays that help match the latency of the controller with the system. However, learning in spiking neural networks poses a problem because of the non-differentiability of spikes. Although there are approximations like surrogate gradient decent for supervised learning, learning algorithms customized for spiking neural networks are required. Moreover, in order to design a compact, application-specific controller, the approximate knowledge of the number of neurons needed for a particular task is of importance, because the size of the chip depends on the number of neurons and synapse compartments on the chip. This work combines both of these needs and investigates the control performance on a cartpole with an adaptive controller by varying the number of neurons. The bob mass is varied and friction is added to the cart and the pole. First, the work shows the implementation of the Prescribed Error Sensitivity (PES) learning rule using a single neuron for the supervised learning of some standard functions, within the Neural Engineering Framework. Next, the work investigates the adaptive control of a cartpole against varying parameters, by progressively reducing the neuron number starting from 20 neurons, to arrive at a minimum number of spiking neurons, when trained with the PES rule. This knowledge is then used to run the adaptive controller on an FPGA board.

关键词： Sensitivity Mechatronics Neuromorphic engineering Neurons Supervised learning Neural engineering Spiking neural networks Logic gates Synapses Standards

来源：评论

学校读者我要写书评

暂无评论

Control of an Under-Actuated Cartpole with an Evolving Neural Topology Using Synaptic Bellman Equation

Control of an Under-Actuated Cartpole with an Evolving Neura...

引用

International Conference on Modern Circuits and systems Technologies (MOCAST)

ISBN: (数字)9798350385427

ISBN: (纸本)9798350385434

This paper proposes a synaptic Q-learning algorithm, for the classical cartpole control problem where the Bell-man equations are incorporated at the synaptic level. This enables the iterative evolution of the network topology as a directed graph during training. Topology evolution, in conjunction with mixed-signal computation, leverages the optimization of the number of neurons and synapses that could be used to design spike-based reinforcement learning accelerators. The proposed architecture has the potential to reduce resource utilization on board, hence creating more compact application-specific neuromorphic ICs.

关键词： Training Q-learning Network topology Neuromorphics Neurons Computer architecture Probabilistic logic

来源：评论

学校读者我要写书评

暂无评论

Preface to Non-Smooth Dynamics Euromech Colloquium Proceedings

Preface to Non-Smooth Dynamics Euromech Colloquium Proceedin...

引用

2023 Euromech Colloquium on Non-smooth dynamical systems, NSDS 2023

作者： Rounak, Aasifa Pakrashi, Vikram Perlikowski, Przemyslaw Litak, Grzegorz UCD Centre for Mechanics Dynamical Systems and Risk Laboratory School of Mechanical and Materials Engineering Ireland Division of Dynamics Lodz University of Technology Stefanowskiego 1/15 Lodz90-924 Poland Faculty of Mechanical Engineering Lublin University of Technology Nadbystrzycka 36 Lublin20-618 Poland

Non-smooth dynamical systems are integral to many engineering applications, including vibration control, energy dissipation, stability analysis, and nonlinear electronic circuits. The growing interest in this field has led to significant advances in theoretical modeling, computational techniques, and experimental validations, which are reflected in the contributions of this proceedings. Such studies are fundamental in understanding and modeling discontinuous behaviors such as impacts, friction, switching, and vibro-impact phenomena. This volume presents a collection of selected papers from NSDS 2023, covering a diverse range of topics that were considered in the colloquium. The articles cover theoretical approaches, computational methods, and experimental investigations, providing a snapshot of some of the current research and future directions in this field. © 2025 Institute of Physics Publishing. All rights reserved.

关键词： Vibration analysis

来源：评论

学校读者我要写书评

暂无评论

Experimental assessment of a semi-submersible floating solar platform subjected to wave and wind loading 6th

Experimental assessment of a semi-submersible floating solar...

引用

6th International Conference on Renewable Energies Offshore, RENEW 2024

作者： Campbell, M. Baruah, G. Karimirad, M. Van, M. Pakrashi, V. School of Natural and Built Environment Queen’s University Belfast Belfast United Kingdom School of Electronics Electrical Engineering and Computer Science Queen’s University Belfast Belfast United Kingdom UCD Centre for Mechanics Dynamical Systems and Risk Laboratory School of Mechanical and Materials Engineering University College Dublin Ireland

ISBN: (纸本)9781032905570

Floating solar platforms are subjected to coupled wave and wind induced responses, straddling the unpredictable wave-wind boundary layer. The simultaneous actions of these coupled responses in real sea conditions are not yet fully investigated for floating solar systems. The fluidstructure interactions are complex due to these coupled responses. The combined response to these wave and wind loads results in a coupled motion and tension in the mooring lines. This paper investigates the wave-only and wave-wind load case scenarios using scaled model wave tank testing. To study these scenarios, the Qualisys motion capture system is used to record the motions of the structure in the tank and load cells to record the mooring loads. This study investigates the correlation of wave, wind, motions, and mooring tension. The contribution of the wind loading component to the coupled wave-wind scenario is assessed and trends are determined for the wind loading contribution effects observed. © 2025 The Author(s).

关键词： Mooring

来源：评论

学校读者我要写书评

暂无评论

Wake-induced response of vibro-impacting systems

arXiv

引用

arXiv 2023年

作者： Chawla, Rohit Rounak, Aasifa Bose, Chandan Pakrashi, Vikram UCD Centre for Mechanics Dynamical Systems and Risk Laboratory School of Mechanical and Materials Engineering University College Dublin Dublin Ireland School of Engineering Institute for Energy Systems University of Edinburgh Edinburgh United Kingdom

The stability and bifurcation behaviour of a wake-induced vibro-impacting oscillator is studied. The effects of a discontinuity on the stability of the structure while it is undergoing phase-locked motions due to the surrounding fluid-structure interactions (FSI) are examined. The primary structure and the near wake dynamics are modelled as a harmonic oscillator and a Van der Pol oscillator, respectively, and are weakly coupled to each other via acceleration coupling. Qualitative changes in the dynamical behaviour of this system are investigated in the context of discontinuity-induced bifurcations (DIBs) that result from the interaction of fluid flow and non-smoothness from the primary structure. Phenomenological behaviours like the co-existence of attractors and period-adding cascades of limit cycles separated by chaotic orbits are observed. The existence of these phenomena is demonstrated via stability analysis using Floquet theory and the associated Lyapunov spectra. In addition, the behaviour of orbits in the local neighbourhood of the barrier is defined using a higher-order transverse discontinuity map. This mapping is implemented to obtain the respective Lyapunov exponents. Solutions obtained using this modified algorithm are demonstrated to accurately predict both stable and chaotic regimes, as observed from the corresponding bifurcation diagrams.. © 2023, CC BY.

关键词： Fluid structure interaction

来源：评论

学校读者我要写书评

暂无评论

Instrumenting an Operational Train for Continuous Monitoring of Bridges and Track 1st

Instrumenting an Operational Train for Continuous Monitoring...

引用

1st Conference of the European Association on Quality Control of Bridges and Structures, EUROSTRUCT 2021

作者： Micu, E. Alexandra Obrien, Eugene Bowe, Cathal Okosun, Favour Osose Morgan, David Pakrashi, Vikram Dynamical Systems and Risk Laboratory School of Mechanical and Materials Engineering University College Dublin Dublin Ireland School of Civil Engineering University College Dublin Dublin Ireland Iarnród Éireann Dublin Ireland Science Foundation Ireland MaREI Centre University College Dublin Dublin Ireland

ISBN: (纸本)9783030918767

A well-designed data acquisition (DAQ) system is essential to collect accurate (bridge and track) data over a long-term period. Direct instrumentation of a single component of the network (e.g. sensors installed on a bridge) is costly and offers minimal data. An instrumented train that operates for a long period of time over the entire network can collect a large amount of data at less expense and maintenance of the system. A measurement system installed on an in-service train for monitoring the Irish Rail Network for a duration of twelve months is proposed here to monitor the track and bridge condition. Uni-axial and tri-axial accelerometers are proposed to instrument sprung and un-sprung masses to measure vibration in the vertical direction and along the three axes. The vibration data are transmitted to and stored in the data logger. A high accuracy GPS system is used for referencing the data to geographical coordinates. An existing power supply on the train powers the data acquisition system. Such instrumentation is fundamental to obtaining information around risk assessment and performance evaluation of critical infrastructures, especially due to their inherent uncertainties. With a system like that described in this paper, investigation into these uncertain systems can be carried out in a systematics manner and without having to close the operations of the structure. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Accelerometers

来源：评论

学校读者我要写书评

暂无评论

Higher-Order Transverse Discontinuity Mapping for Accurate Stability Analysis of Hybrid dynamical systems

SSRN

引用

SSRN 2024年

作者： Chawla, Rohit Rounak, Aasifa Pakrashi, Vikram aUCD Centre for Mechanics Dynamical Systems and Risk Laboratory School of Mechanical and Materials Engineering University College Dublin Dublin Ireland bSFI MaREI Centre University College Dublin Dublin Ireland cUCD Energy Institute University College Dublin Dublin Ireland

This article aims to minimise the inconsistencies in the results obtained by discontinuity mapping and directnumerical observations in terms of stability analysis. It demonstrates the pitfalls of locally linearizing hybridnonlinear dynamical systems in the vicinity of discontinuity boundaries and how it leads to incorrect estimatesof impact occurrences for transverse interactions with a rigid barrier. A higher-order transverse discontinuitymapping (TDM) is proposed to overcome this shortcoming, allowing for better analytical estimation of impactoccurrence times, state transitions, and, consequently, the trajectories. The difference in flight times of twoclosely initiated trajectories in the local neighbourhood of a discontinuity boundary is estimated up to O(2).This results in a quadratic equation that implies that orbits local to the impacting state, corresponding toa negative discriminant, cannot reach the discontinuity barrier. Further, the O(2) correction terms to theanalytical expression of the discontinuity mapping ensures that the flight time estimates do not diverge forlow-velocity impacts near grazing, thereby avoiding overestimation of the mapped state. A numerical methodis developed that estimates a saltation matrix incorporating the proposed higher-order TDM to avoid incorrectimpact occurrences. Two algorithms are proposed to estimate the Lyapunov spectra and Floquet multipliers,ensuring the state of stability is appropriately computed. Stability analyses are carried out using the proposedhigher-order approach for representative cases of a hard impact oscillator and a pair impact oscillator, withresults consistent with numerically derived bifurcation diagrams. © 2024, The Authors. All rights reserved.

关键词： Hybrid systems

来源：评论

学校读者我要写书评

暂无评论

Deep-Learning-based damage detection of an experimentally tested full-scale wind turbine blade.

e-Journal of Nondestructive Testing

引用

e-Journal of Nondestructive Testing 2024年第7期29卷

Reducing the operation and maintenance (O&M) costs of wind farms can foster adoption of environmentally sustainable and cost-effective energy sources. O&M costs in Wind Turbines can account up to 35% of the turbine’s total levelized cost per KWh, with a large portion attributed to that for wind turbine blades (WTB). In the present study, an experimental campaign for fatigue damage progression monitoring is presented. After subjecting the WTB to cyclic loading, an artificial transverse crack was introduced in the trailing edge (TE).The dynamic response of the blade to three different excitation schemes-white noise, white noise with the inclusion of a fundamental sinusoidal component and a frequency sweep-is obtained via the use of accelerometers, strain gauges and a real-time deflection monitoring system. These tests yielded generated 4 different health states, the initial healthy and 3 damaged states. The progressive damage is presented using frequency response functions (FRFs),while a simple deep-learning damage detection framework is developed. A conventional autoencoder (AE) is trained using the Frequency Response Functions (FRFs) corresponding to the blade’s healthy state;then, an unsupervised damage detection algorithm is formulated using the AE. © 2024, NDT. net GmbH and Co. KG. All rights reserved.

关键词： Damage detection

来源：评论

学校读者我要写书评

暂无评论

Exploring Chaos and Ergodic behavior of an Inductorless Circuit driven by Stochastic Parameters

arXiv

引用

arXiv 2023年

作者： Seth, Soumyajit Bera, Abhijit Pakrashi, Vikram UCD Centre for Mechanics Dynamical Systems and Risk Laboratory School of Mechanical and Materials Engineering University College Dublin Ireland Department of Physical Sciences Indian Institute of Science Education and Research Kolkata Mohanpur Campus 741246 India

There exist extensive studies on periodic and random perturbations of various continuous maps investigating their dynamics. This paper presents a random piecewise smooth map derived from a simple inductor-less switching circuit. The bifurcation parameter is bounded and randomly selected from a stationary distribution. Due to the stochasticity inherent in either the parameter values or the state variable, the time evolution of the state variable cannot be predicted at a specific time instant. We observe that the state variable exhibits completely ergodic behavior when the minimum value of the parameter is 2.0. However, the ensemble average of the state variable converges to a fixed value. For parameter values ranging from 2.0 to 3.5, the system demonstrates nonchaotic behavior and the absolute value of the Lyapunov exponent increases monotonically with the asymmetry (ap) of the distribution from which the bifurcation parameter values are sampled. We determine the probability density function of the random map and verify its invariance under any initial condition. The most noteworthy result is the disappearance of chaotic behavior when the lower range of the distribution is varied while maintaining a fixed upper threshold for a particular distribution, even though the nonrandom map exhibits an array of periodic and chaotic behaviors within that range. © 2023, CC BY.

关键词： Timing circuits

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：