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Study on excitation force characteristics in a coupled shaker-structure system considering structure modes coupling

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Chinese Journal of Aeronautics 2022年第7期35卷 227-245页

作者： Guiwei ZHANG Xiaochen WANG zhichun yang School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

The interaction between an elastic structure and electrodynamic shakers commonly exists in Ground Flutter Simulation Tests(GFST)with multi-point excitations,causing a considerable discrepancy between the practical excitation forces and desired *** investigate the excitation force characteristics on a cantilever beam excited by a voltage-sourced electrodynamic shaker,the coupled shaker-beam system is modeled to derive the excitation force formula using Hamilton’s principle and Galerkin’s *** results using the multi-mode beam model coupled with the shaker model are in good agreement with experimental results,verifying that the proposed multi-mode method can accurately predict the excitation ***,parametric studies show that the influence of system parameters on the excitation force is related to the shaker’s operating *** in current mode of shaker,when the beam resonant frequency approaches the suspension frequency of shaker armature,the variation of excitation force amplitude in voltage mode is no longer ***,if the exciting point in the GFST is located far away from the modal node,it is essential to compensate the force because the accuracy of tests can be reduced *** coupled shaker-beam model proposed in this paper can provide the basis for compensation measures.

关键词： Electrodynamic shaker Force characteristics Galerkin’s approach Lumped parameter model Parameters estimation

Bandgap formation and low-frequency structural vibration suppression for stiffened plate-type metastructure with general boundary conditions

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Chinese Journal of Aeronautics 2023年第10期36卷 210-228页

作者： Tian ZHAO zhichun yang Yanlong XU Wei TIAN School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

Metastructures with unique mechanical properties have shown attractive potential application in vibration and noise ***,most of the metastructures deal with the vibration bandgap properties of infinite structures without considering specific boundary condition and dynamic behaviors,which cannot be directly applied to the engineering *** this research,we design a Stiffened Plate-type Metastructure(SPM)composed of a plate with periodic stiffeners and cantilever beam-type resonators subjected to general boundary conditions for low-frequency vibration *** effects of boundary conditions and the number and orientation of the stiffeners on Locally Resonant(LR)type bandgap properties in SPM are further *** analytical modeling framework is developed to predict the bandgap formations and vibration behaviors of SPMs in finite-size *** governing equations of the SPM reinforced by various arrangements of stiffeners are derived based on the first-order shear deformation theory and Hamilton’s principle,and a Fourier series combined with auxiliary functions is employed to satisfy the arbitrary boundary *** element analysis and experimental investigations of vibration behaviors for the SPM are carried out to validate the accuracy and reliability of the present analytical *** practical designs of the SPMs with specific boundary conditions,it is found that there exist optimal numbers of stiffeners and resonators which can produce the significant LR-type bandgap ***,various arrangements of stiffeners and resonators are explored for different boundary conditions by breaking the requirement of spatially *** is shown that for the designed SPM,the vibration modes of its host structure should be considered to widen the frequency range in which the resonators transfer and store energy,and hence improve the performance of low-frequency vibration *** present work can pro

关键词： Bandgap Locally resonant Metastructure Stiffened plate Vibration suppression

Suppressing nonlinear aeroelastic response of laminated composite panels in supersonic airflows using a nonlinear energy sink

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Chinese Journal of Aeronautics 2021年第2期34卷 376-385页

作者： Jian ZHOU Minglong XU zhichun yang Yingsong GU State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace EngineeringXi'an Jiaotong UniversityXi'an 710049China School of Aeronautics Northwestern Polyteclmical UniversityXi'an 710072China

This paper proposes using a Nonlinear Energy Sink(NES) to suppress the nonlinear aeroelastic response of laminated composite panels in supersonic airflows. Relevant aeroelastic equations are established using Hamilton’s principle and a finite element approach, drawing upon Von Karman’s large deflection theory and first order piston theory. The idea of the NES suppression region is proposed and the effects of NES parameters on the NES suppression region are studied in detail. The results show that the nonlinear aeroelastic responses of the panel can be completely suppressed by the Transient Resonance Capture(TRC);the appropriate NES parameter values can increase the critical dynamic pressure for flutter and suppress the nonlinear aeroelastic response effectively. Increasing the mass ratio of the NES can improve the NES suppression region;the nonlinear stiffness coefficient and damping of the NES within a specific range can suppress the nonlinear aeroelastic response. The most effective installation position for a NES is in a specific region behind the center-line of the panel in the direction of the airflow.

关键词： Aeroelasticity Laminated composite panel Nonlinear dynamics Nonlinear energy sink Panel flutter Passive suppression

Robust control of exciting force for vibration control system with multi-exciters

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Science China(Technological Sciences) 2013年第10期56卷 2516-2524页

作者： SONG QiaoZhi yang zhichun WANG Wei Institute of Structural Dynamics and Control School of Aeronautics Northwestern Polytechnical University

Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to be,especially when multi-exciters are used as actuators to precisely actuate large flexible *** is necessary to consider these effects to ensure the force generated by each exciter is the same as *** this paper,a robust control method is proposed for the multi-input and multi-output(MIMO)structural vibration control system to trace the target actuating force of each exciter.A special signal is designed and put into the coupled mul-ti-exciter-structure system,and the input and output signals of the system are used to build a dynamic model involving both the dynamical characters of the exciters and the structure using the subspace identification *** the uncertainty factors of the multi-exciter/structure system,an H-infinity robust controller is designed to decouple the coupling between structure and exciters based on the identified system model.A MIMO vibration control system combined with a flexible plate and three electromagnetic exciters is adopted to demonstrate the proposed method,both numerical simulation and model experiments showing that the output force of each exciter can trace its target force accurately within the requested frequency band.

关键词： multi-exciters system exciting force control subspace identification robust control experiment modeling

Aeroelastic effect on aerothermoacoustic response of metallic panels in supersonic flow

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Chinese Journal of Aeronautics 2016年第6期29卷 1635-1648页

作者： Wang Xiaochen yang zhichun Zhou Jian Hu Wei School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Xi’an Aerospace Propulsion Institute Xi’an 710100China

A finite element formulation is presented for the analysis of the aeroelastic effect on the aerothermoacoustic response of metallic panels in supersonic flow. The first-order shear deformation theory(FSDT) and the von Karman nonlinear strain-displacement relationships are employed to consider the geometric nonlinearity induced by large deflections. The piston theory and the Gaussian white noise are used to simulate the mean flow aerodynamics and the turbulence from the boundary layer. The thermal loading is assumed to be steady and uniformly distributed, and the material properties are assumed to be temperature independent. The governing equations of motion are firstly formulated in structural node degrees of freedom by using the principle of virtual work,and then transformed and reduced to a set of coupled nonlinear Duffing oscillators in modal coordinates. The dynamic response of a panel is obtained by the Runge-Kutta integration method. The results indicate that the increasing aeroelastic effect can lead the panel vibration from a random motion to a highly ordered motion in the fashion of diffused limit cycle oscillations(LCOs), and remarkably alter the stochastic bifurcation and the spectrum of the aerothermoacoustic *** the other hand there exists a counterbalance mechanism between the external random loading and the aeroelastic effect, which mainly functions through the nonlinear frequency-amplitude response. It is surmised that the aeroelastic effect must be considered in sonic fatigue analysis for panel structures in supersonic flow.

关键词： Aeroelastic effect Aerothermoacoustic response Metallic panels Nonlinear frequencyamplitude response Sonic fatigue

Robust flutter analysis based on genetic algorithm

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Science China(Technological Sciences) 2012年第9期55卷 2474-2481页

作者： GU YingSong ZHANG XinPing yang zhichun Institute of Structural Dynamics and Control Northwestern Polytechnical UniversityXi'an 710072China A VIC Shaanxi Aircraft Industry(Group)Corporation LTD. Hanzhong 723213China

Robust flutter analysis considering model uncertain parameters is very important in theory and engineering *** robust flutter solution based on structured singular value subject to real parametric uncertainties may become difficult because the discontinuity and increasing complexity in real mu *** is crucial to solve the worst-case flutter speed accurately and efficiently for real parametric *** this paper,robust flutter analysis is formulated as a nonlinear programming *** proper nonlinear programming technique and classical flutter analysis method,the worst-case parametric perturbations and the robust flutter solution will be captured by optimization *** the derived nonlinear programming problem,the parametric uncertainties are taken as design variables bounded with perturbed intervals,while the flutter speed is selected as the objective *** model is optimized by the genetic algorithm with promising global optimum *** present approach avoids calculating purely real mu and makes robust flutter analysis a plain *** is illustrated by a special test case that the robust flutter results coincide well with the exhaustive *** is also demonstrated that the present method can solve the match-point robust flutter solution under constant Mach number accurately and *** method is implemented in problem with more uncertain parameters and asymmetric perturbation interval.

关键词： Flutter genetic algorithm robust flutter analysis match-point solution nonmatch-point solution

Boundary condition modelling and identification for cantilever-like structures using natural frequencies

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Chinese Journal of Aeronautics 2019年第6期32卷 1451-1464页

作者： Wei LIU zhichun yang Le WANG Ning GUO School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Xi’an Aerospace Propulsion Institute Xi’an 710100China

The actual boundary conditions of cantilever-like structures might be non-ideally clamped in engineering practice, and they can also vary with time due to damage or aging. Precise modelling of boundary conditions, in which both the boundary stiffness and the boundary mass should be modelled correctly, might be one of the most significant aspects in dynamic analysis and testing for such structures. However, only the boundary stiffness was considered in the most existing methods. In this paper, a boundary condition modelling and identification method for cantilever-like structures is proposed to precisely model both the boundary stiffness and the boundary mass using sensitivity analysis of natural frequencies. The boundary conditions of a cantilever-like structure can be parameterized by constant mass, constant rotational inertia,constant translational stiffness, and constant rotational stiffness. The relationship between natural frequencies and boundary parameters is deduced according to the vibration equation for the lateral vibration of a non-uniform beam. Then, an iterative identification formulation is established using the sensitivity analysis of natural frequencies with respect to the boundary parameters. The regularization technique is also used to solve the potential ill-posed problem in the identification *** simulations and experiments are performed to validate the feasibility and accuracy of the proposed method. Results show that the proposed method can be utilized to precisely model the boundary parameters of a cantilever-like structure.

关键词： Boundary condition identification Boundary condition modelling Iterative method Natural frequency Sensitivity analysis

Design of low-frequency circular metastructure isolators with high-load-bearing capacity

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Chinese Journal of Aeronautics 2024年第10期37卷 207-220页

作者： Ning CHEN zhichun yang Te yang Yizhou SHEN Wei TIAN Yanlong XU School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory of Strength and Structural Integrity Xi’an 710065China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an 710049China

Traditional vibration isolation structures cannot work effectively for low-frequency vibration under heavy loads,due to the inherent contradiction between the high-static and lowdynamic stiffness of these *** the challenge can be effectively addressed by introducing a negative stiffness mechanism,the existing structures inevitably have complex ***,a class of man-made structures with both extraordinary mechanical properties and simple configurations,provide a new insight for low-frequency vibration isolation *** this paper,circular metastructure isolators consisting of some simple beams are designed for low-frequency vibration,including a single-layer isolator and a double-layer isolator,and their static and dynamic characteristics are studied,*** the static characteristic,the force–displacement and stiffness–displacement curves are obtained by finite element simulation;for the dynamic characteristic,the vibration transmissibility curves are obtained analytically and *** result shows that the circular nonlinear single-layer isolator has excellent lowfrequency isolation performance,and the isolation frequency band will decrease about 20 Hz when the isolated mass is fixed at 1.535 kg,compared with a similar circular linear *** static and dynamic properties are well verified through *** work provides an innovative approach for the low-frequency vibration isolation and has wide potential applications in aeronautics.

关键词： Isolator Low-frequency Curved beam Metastructure Stiffness

Recent progress on flutter‐based wind energy harvesting

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International Journal of Mechanical System Dynamics 2022年第1期2卷 82-98页

作者： Zhiyuan Li Shengxi Zhou zhichun yang School of Aeronautics Northwestern Polytechnical UniversityXi'anChina Research&Development Institute in Shenzhen Northwestern Polytechnical UniversityShenzhenChina

Wind energy harvesting technology can convert wind energy into electric energy to supply power for microelectronic *** has great potential in many specific applications and environments,such as remote areas,sea surfaces,mountains,and so *** the past few years,flutter‐based wind energy harvesting,which generates electric energy based on the limit cycle oscillation created by structural aeroelastic instability,has received increasing attention,and as a consequence,different energy harvesting structures,theories,and methods have been *** this paper,three types of flutter‐based energy harvesters(FEHs)including airfoil‐based,flat plate‐based,and flexible body‐based FEHs are reviewed,and related concepts and theoretical models are *** recent progress in FEH performance enhancement methods is classified into structural improvement and optimization,the introduction of nonlinearity,and hybrid structures and ***,the main FEH challenges are summarized,and future research directions are discussed.

关键词： dynamics flutter performance enhancement wind energy harvesting working principle