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SSRN 2023年

作者： Zhang, Sen Ma, Yongbin Yan, Meng Deng, Zichen School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China

A symplectic space wave propagation method is proposed for the forced vibration of the Acoustic Black Hole (ABH) assemblies. The governing differential equations for vibration of the ABH beam is first converted into Hamiltonian canonical equations. A symplectic eigenvalue problem is then formed, and the wave propagation parameters and wave shapes are obtained analytically. Secondly, A Gaussian point scheme is subsequently used to discrete the ABH beam, while the presented method is used to evaluate the wave amplitude at each point. Various coupling forms are considered for the ABH assemblies, in which the ABH beams are coupled directly or through a joint. The wave propagation method based on symplectic analysis is used to describe the vibration of ABH beams and the finite element method is used to describe the vibration of the joint. By using the displacement continuity and equilibrium of force at the connection interface, the dynamic coupling between the ABH beam and the joint is established. Since the presented method utilizes symplectic analytical solutions of wave modes, the computational efficiency and precision are high that are verified by several numerical examples. © 2023, The Authors. All rights reserved.

关键词： Eigenvalues and eigenfunctions

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Rotating machinery fault diagnosis based on convolutional neural network and infrared thermal imaging

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Chinese Journal of Aeronautics 2020年第2期33卷 427-438页

作者： Yongbo LI Xiaoqiang DU Fangyi WAN Xianzhi WANG Huangchao YU MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China Institute of Unmanned System National University of Defense TechnologyChangsha 410073China

Rotating machinery is widely applied in industrial *** diagnosis of rotating machinery is vital in manufacturing system,which can prevent catastrophic failure and reduce financial ***,Deep Learning(DL)-based fault diagnosis method becomes a hot *** Neural Network(CNN)is an effective DL method to extract the features of raw data *** paper develops a fault diagnosis method using CNN for InfRared Thermal(IRT)***,IRT technique is utilized to capture the IRT images of rotating ***,the CNN is applied to extract fault features from the IRT *** the end,the obtained features are fed into the Softmax Regression(SR)classifier for fault pattern *** effectiveness of the proposed method is validated using two different experimental *** show that the proposed method has a superior performance in identification various faults on rotor and bearings comparing with other deep learning models and traditional vibration-based method.

关键词： Convolutional neural network Feature extraction Infrared thermography(IRT) Intelligent fault diagnosis Rotating machinery

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A Meta-Design of Hollow-Square-Frustum-Core Sandwich Structures for Improved Compression and Vibration Isolation Properties

SSRN

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SSRN 2024年

作者： Zhang, Kai Ding, Bin Shi, Haizhou Hong, Fang Gu, Xudong Deng, Zichen School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian116024 China

Metamaterials can satisfy the demand for lightweight and multifunctional structures. In this study, we propose a double hollow-square-frustum-core sandwich meta-structure (meta-DHSFCSS) for vibration isolation. The out-of-plane compressive performance of the sandwich meta-structure specimen is experimentally and numerically studied. The bandgap in the band structure for out-of-plane vibration of the meta-DHSFCSS is numerically computed and verified by the frequency-domain and time-domain responses and vibration test. Parameter study is performed on the meta-DHSFCSS to investigate the effects on the structural compressive performance and vibration isolation property. The maximum load-mass ratio exceeds 283 N/g and the maximum SEA reaches 2000 kJ/kg. These two indexes are dramatically better than those of certain previous studies. The meta-DHSFCSS has a wide bandgap for vibration isolation. Gradient design and waveguide design are introduced to the meta-DHSFCSS supercell. Its vibration isolation property is improved. The locational and directional transmission of the elastic wave can be achieved by the rainbow trapping effect of gradient meta-DHSFCSS and the waveguides with different transmission routes. These demonstrate the great application of the meta-DHSFCSS in elastic wave manipulation. © 2024, The Authors. All rights reserved.

关键词： Metamaterials

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Entropic stochastic resonance of finite-size particles in confined Brownian transport

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Physical Review E 2024年第5期109卷 054110-054110页

作者： Hai-Wei Hu Lin Du Ai-Li Fan Zi-Chen Deng Celso Grebogi School of Mathematics and Statistics Northwestern Polytechnical University Xi'an 710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi'an 710072 China School of Aeronautics Northwestern Polytechnical University Xi'an 710072 China Institute for Complex Systems and Mathematical Biology Kingdom College University of Aberdeen Aberdeen AB24 3UE United Kingdom

We demonstrate the existence of entropic stochastic resonance (ESR) of passive Brownian particles with finite size in a double- or triple-circular confined cavity, and compare the similarities and differences of ESR in the double-circular cavity and triple-circular cavity. When the diffusion of Brownian particles is constrained to the double- or triple-circular cavity, the presence of irregular boundaries leads to entropic barriers. The interplay between the entropic barriers, a periodic input signal, the gravity of particles, and intrinsic thermal noise may give rise to a peak in the spectral amplification factor and therefore to the appearance of the ESR phenomenon. It is shown that ESR can occur in both a double-circular cavity and a triple-circular cavity, and by adjusting some parameters of the system, the response of the system can be optimized. The differences are that the spectral amplification factor in a triple-circular cavity is significantly larger than that in a double-circular cavity, and compared with the ESR in a double-circular cavity, the ESR effect in a triple-circular cavity occurs within a wider range of external force parameters. In addition, the strength of ESR also depends on the particle radius, and smaller particles can induce more obvious ESR, indicating that the size effect cannot be safely neglected. The ESR phenomenon usually occurs in small-scale systems where confinement and noise play an important role. Therefore, the mechanism that is found could be used to manipulate and control nanodevices and biomolecules.

关键词： Brownian motion Stochastic dynamical systems Brownian dynamics Fokker–Planck equation Langevin equation

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Fixed-interval smoothing of an aeroelastic airfoil model with cubic or free-play nonlinearity in incompressible flow

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Acta Mechanica Sinica 2021年第7期37卷 1168-1182,I0003页

作者： Qi Liu Yong Xu Yongge Li Jurgen Kurths Xiaochuan Liu School of Mathematics and Statistics Northwestern Polytechnical UniversityXi’an 710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an 710072China Potsdam Institute for Climate Impact Research Potsdam 14473Germany Lobachevsky University of Nizhny Novgorod Nizhnij NovgorodRussia AVIC Aircraft Strength Research Institute Xi’an 710065China

Fixed-interval smoothing,as one of the most important types of state estimation,has been concerned in many practical problems especially in the analysis of flight test ***,the existing sequential filters and smoothers usually cannot deal with nonlinear or high-dimensional systems well.A state-of-the-art technique is employed in this study to explore the fixed-interval smoothing problem of a conceptual two-dimensional airfoil model in incompressible flow from noisy measurement ***,the governing equations of the airfoil model are assumed to be known or only partially known.A single objective optimization problem is constructed with the classical Runge–Kutta scheme,and then estimations of the system states,the measurement noise and even the unknown parameters are obtained simultaneously through minimizing the objective *** and feasibility of the method are examined under several simulated measurement data corrupted by different measurement *** the obtained results indicate that the introduced algorithm is applicable for the airfoil model with cubic or free-play structural nonlinearity and leads to accurate state and parameter ***,it is highly robust to Gaussian white and even more complex heavy-tailed measurement *** should be emphasized that the employed algorithm is still effective to high-dimensional nonlinear aeroelastic systems.

关键词： Airfoil model Incompressible flow State estimation Parameter estimation

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Open-/Closed-loop Active Learning for Data-driven Predictive control

arXiv

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arXiv 2024年

作者： Feng, Shilun Shi, Dawei Shi, Yang Zheng, Kaikai The State Key Laboratory of Intelligent Control and Decision of Complex Systems MIIT Key Laboratory of Servo Motion System Drive and Control School of Automation Beijing Institute of Technology Beijing100081 China The Department of Mechanical Engineering Faculty of Engineering University of Victoria VictoriaBCV8N 3P6 Canada

An important question in data-driven control is how to obtain an informative dataset. In this work, we consider the problem of effective data acquisition of an unknown linear system with bounded disturbance for both open-loop and closed-loop stages. The learning objective is to minimize the volume of the set of admissible systems. First, a performance measure based on historical data and the input sequence is introduced to characterize the upper bound of the volume of the set of admissible systems. On the basis of this performance measure, an open-loop active learning strategy is proposed to minimize the volume by actively designing inputs during the open-loop stage. For the closed-loop stage, an closed-loop active learning strategy is designed to select and learn from informative closed-loop data. The efficiency of the proposed closed-loop active learning strategy is proved by showing that the unselected data cannot benefit the learning performance. Furthermore, an adaptive predictive controller is designed in accordance with the proposed data acquisition approach. The recursive feasibility and the stability of the controller are proved by analyzing the effect of the closed-loop active learning strategy. Finally, numerical examples and comparisons illustrate the effectiveness of the proposed data acquisition strategy. Copyright © 2024, The Authors. All rights reserved.

关键词： Active learning

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Thermoelastic Modeling and Transient Responses with Piezoelectric and Size Effects

SSRN

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SSRN 2024年

作者： Li, Si-Yang Wu, Hua Yu, Ya-Jun School of Mechanics Civil Engineering and Architecture Northwestern Polytechnical University Xi’an710072 China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China School of Aeronautics Northwestern Polytechnical University Xi’an710072 China National Key Laboratory of Strength and Structural Integrity Xi’an710072 China

Generalized piezoelectric thermoelastic models play significantly important role in multi-field coupling analysis, especially in extreme environments, of nanosensors, nanogenerators and superconductivity. In this work, generalized thermoelastic theory is firstly proposed by considering higher-order thermal lagging and size effect. Then, unified generalized piezoelectric thermoelastic coupling model is obtained by further combining piezoelectric effect. Transient piezoelectric thermoelastic responses of piezoelectric materials under thermal shock are investigated. Numerical results are obtained from analytical solution in Laplace domain by adopting numerical inverse Laplace transform. The obtained results are graphically illustrated, from which the effects of lagging effect and size effect are clarified. This work provides theoretical model and numerical method to predict transient thermoelastic behaviors of piezoelectric materials across different time and space scales. © 2024, The Authors. All rights reserved.

关键词： Transient analysis

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Frequency comb in a parametrically modulated micro-resonator

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Acta Mechanica Sinica 2022年第11期38卷 79-88页

作者： Xuefeng Wang Qiqi Yang Zhan Shi Ronghua Huan Weiqiu Zhu Xingjian Jing Zichen Deng Xueyong Wei Department of Engineering Mechanics MIIT Key Laboratory of Dynamics and Control of Complex SystemsNorthwestern Polytechnical UniversityXi’an710072China Department of Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang UniversityHangzhou310027China State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an710049China Department of Mechanical Engineering City University of Hong KongHong Kong999077China

In this paper,we report the frequency comb response experimentally and analytically in a rhombic micro-resonator with parametrical *** the electrostatically actuated rhombic micro-resonator is modulated axially by a low-frequency periodic excitation,a comb-like vibration response with few equidistant positioned fingers in the frequency domain is *** finger spacing of frequency comb response is exactly consistent with modulation frequency and the number and amplitude of the fingers can be tuned by modulation strength.A mixed frequency comb with extra comb fingers is further generated when the resonator is modulated simultaneously by two different low-frequency excitation *** adjusting the relation of the two modulation frequencies,unequal spacing frequency combs are achieved for the first time,which leads to a more flexible tunability of the comb spacing for different *** analysis based on the dynamic model well explains the corresponding observations.

关键词： Micro-resonator Nonlinear dynamics Vibration Parametrical modulation Frequency comb

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Residual-Based Multi-peak Sampling Algorithm in Inverse Problems of Dynamical systems

arXiv

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arXiv 2023年

作者： An, Xiao-Kai Du, Lin Deng, Zi-Chen Zhang, Yu-Jia Miit Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi'An710072 China School of Mathematics and Statistics Northwestern Polytechnical University Xi'An710072 China School of Aeronautics Northwestern Polytechnical University Xi'An710072 China

Stochastic differential equations can describe a wide range of dynamical systems, and obtaining the governing equations of these systems is the premise of studying the nonlinear dynamic behavior of the system. Neural networks are currently the most popular approach in the inverse problem of dynamical systems. In order to obtain accurate dynamical equations, neural networks need a large amount of trajectory data as a training set. To address this shortcoming, we propose a residual-based multi-peaks sampling algorithm. Evaluate the training results of each epoch of neural network, calculate the probability density function P(x) of the residual, perform sampling where the P(x) is large, and add samples to the training set to retrain the neural network. In order to prevent the neural network from falling into the trap of overfitting, we discretize the sampling points. We conduct case studies using two classical nonlinear dynamical systems and perform bifurcation and first escape probability analyzes of the fitted equations. Results show that our proposed sampling strategy requires only 20∼30% of the sample points of the original method to reconstruct the stochastic dynamical behavior of the system. Finally, the algorithm is tested by adding interference noise to the data, and the results show that the sampling strategy has better numerical robustness and stability. Copyright © 2023, The Authors. All rights reserved.

关键词： Dynamical systems

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Data-Driven Learning and control with Event-Triggered Measurements

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IEEE Transactions on Automatic control 2025年

作者： Feng, Shilun Shi, Dawei Chen, Tongwen Shi, Ling Beijing Institute of Technology State Key Laboratory of Intelligent Control and Decision of Complex Systems MIIT Key Laboratory of Servo Motion System Drive and Control School of Automation Beijing100081 China University of Alberta Department of Electrical and Computer Engineering EdmontonABT6G 1H9 Canada Hong Kong University of Science and Technology Department of Electronic and Computer Engineering Clear Water Bay Kowloon Hong Kong

Event-triggered control has attracted considerable attention for its effectiveness in resource-restricted applications. To make event-triggered control as an end-to-end solution, a key issue is how to effectively learn unknown system dynamics from event-triggered measurements and consequently, develop a learning-based event-triggered controller. Existing works learn system dynamics based on periodic time-triggered measurements, and it is yet to know how to learn a controller with performance guarantee based on event-triggered measurements. To address this issue, we consider the problem of learning an event-triggered state feedback controller for an unknown linear system based on event-triggered state measurements in this work. In particular, we first analyze the event-triggered measurements within a set-membership framework. We prove that the estimation error belongs to a bounded ellipsoid determined by the historical measurements and the event-triggering condition. Subsequently, we demonstrate that all admissible systems compatible with the collected data samples can be explicitly represented in the form of quadratic matrix inequalities using the state estimates. With the acquired set of admissible systems, a co-design problem for the data-driven controller and event-triggering condition is solved using the linear matrix inequality technique, with guaranteed closed-loop stability and L2-gain performance. Finally, numerical examples and comparisons are provided to illustrate the effectiveness of the proposed event-triggered learning and control approach. © 1963-2012 IEEE.

关键词： Networked control systems

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