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Identification of reduced-order model for an aeroelastic system from flutter test data

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Chinese Journal of Aeronautics 2017年第1期30卷 337-347页

作者： Tang Wei Wu Jian Shi Zhongke School of Automation Northwestern Polytechnical University

Recently, flutter active control using linear parameter varying（LPV） framework has attracted a lot of attention. LPV control synthesis usually generates controllers that are at least of the same order as the aeroelastic models. Therefore, the reduced-order model is required by synthesis for avoidance of large computation cost and high-order controller. This paper proposes a new procedure for generation of accurate reduced-order linear time-invariant（LTI） models by using system identification from flutter testing data. The proposed approach is in two steps. The well-known poly-reference least squares complex frequency（p-LSCF） algorithm is firstly employed for modal parameter identification from frequency response measurement. After parameter identification,the dominant physical modes are determined by clear stabilization diagrams and clustering technique. In the second step, with prior knowledge of physical poles, the improved frequencydomain maximum likelihood（ML） estimator is presented for building accurate reduced-order model. Before ML estimation, an improved subspace identification considering the poles constraint is also proposed for initializing the iterative procedure. Finally, the performance of the proposed procedure is validated by real flight flutter test data.

关键词： Aeroelastic system Flutter test Maximum likelihood reduced-order model Subspace identification

A nonlinear POD reduced order model for limit cycle oscillation prediction

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Science China(Physics,Mechanics & Astronomy) 2010年第7期53卷 1325-1332页

作者： CHEN Gang LI YueMing YAN GuiRong MOE Key Laboratory for Strength&Vibration College of AerospaceXi’an Jiaotong UniversityXi’an 710049China

As the amplitude of the unsteady flow oscillation is large or large changes occur in the mean background flow such as limit cycle oscillation,the traditional proper orthogonal decomposition reduced order model based on linearized time or frequency domain small disturbance solvers can not capture the main nonlinear features.A new nonlinear reduced order model based on the dynamically nonlinear flow equation was *** nonlinear second order snapshot equation in the time domain for proper orthogonal decomposition basis construction was obtained from the Taylor series expansion of the flow *** NLR 7301 airfoil configuration and Goland+ wing/store aeroelastic model were used to validate the capability and efficiency of the new nonlinear reduced order *** simulation results indicate that the proposed new reduced order model can capture the limit cycle oscillation of aeroelastic system very well,while the traditional proper orthogonal decomposition reduced order model will lose effectiveness.

关键词： reduced-order model limit cycle oscillation proper orthogonal decomposition aeroelasticity

Comparative study of reduced-order modeling method for the cavitating flow over a hydrofoil

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Journal of Hydrodynamics 2023年第4期35卷 679-699页

作者： Yan-zhao Wu Ran Tao Di Zhu Ruo-fu Xiao College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing100083China College of Engineering China Agricultural UniversityBeijing100083China

As a high-dimensional complex nonlinear dynamic system,the analysis of the essence of flow has always been a difficult problem,especially in the flow including phase *** recent years,it has become a feasible method to reduce the dimension of flow structure by reduced-order modeling(ROM)*** this paper,through the cavitation numerical simulation of NACA0015 hydrofoil,two ROM methods are used to reduce and restore three different cavitation respectively-proper orthogonal decomposition(POD)and dynamic mode decomposition(DMD).The applicability of two methods in cavitation is discussed and reasons are *** results show that for stable cavitation,POD,DMD methods can accurately restore the flow field of a few modes with high *** unstable cavitation,only POD method can restore real flow field *** situation is mainly due to the fact that POD,DMD method are applicable to different energy ratios,and different main mode selection criterion of DMD will lead to different main *** can greatly simplify the complexity of *** a reasonable ROM can improve the accuracy of a small amount of database,and provide a basis for intelligent prediction of flow analysis.

关键词： Hydrofoil cavitation reduced-order model proper orthogonal decomposition dynamic mode decomposition

reduced-order modeling and Dynamic Stability Analysis of MTDC Systems in DC Voltage Control Timescale

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CSEE Journal of Power and Energy Systems 2020年第3期6卷 591-600页

作者： Li Guo Pengfei Li Xialin Li Fei Gao Di Huang Chengshan Wang Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjin 300072China Shanghai Jiao Tong University Shanghai 200240China Guangzhou Power Supply Bureau of Guangdong Power Grid Co. Ltd.Guangzhou 510620China

An equivalent source-load MTDC system including DC voltage control units,power control units and interconnected DC lines is considered in this paper,which can be regarded as a generic structure of low-voltage DC microgrids,mediumvoltage DC distribution systems or HVDC transmission systems with a common DC bus.A reduced-order model is proposed with a circuit structure of a resistor,inductor and capacitor in parallel for dynamic stability analysis of the system in DC voltage control *** relationship between control parameters and physical parameters of the equivalent circuit can be found,which provides an intuitive insight into the physical meaning of control *** this model,a second-order characteristic equation is further derived to investigate system dynamic stability mechanisms in an analytical *** a result,the system oscillation frequency and damping are characterized in a straight forward manner,and the role of electrical and control parameters and different system-level control strategies in system dynamic stability in DC voltage control timescale is *** effectiveness of the proposed reduced-order model and the correctness of the theoretical analysis are verified by simulation based on PSCAD/EMTDC and an experiment based on a hardware low-voltage MTDC system platform.

关键词： DC voltage control timescale dynamic stability equivalent source-load MTDC system reduced-order model second-order characteristic equation

Self-consistent Clustering Analysis-Based Moving Morphable Component(SMMC)Method for Multiscale Topology Optimization

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固体力学学报（英文版） 2023年第6期36卷 884-898页

作者： Yangfan Li Jiachen Guo Hengyang Li Huihan Chen Department of Mechanical Engineering Northwestern UniversityEvanstonIL 60208USA Theoretical and Applied Mechanics Program Northwestern UniversityEvanstonIL 60208USA Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

Current multiscale topology optimization restricts the solution space by enforcing the use of a few repetitive microstruc-tures that are predetermined,and thus lack the ability for structural concerns like buckling strength,robustness,and ***,in this paper,a new multiscale concurrent topology optimization design,referred to as the self-consistent analysis-based moving morphable component(SMMC)method,is *** with the conventional moving morphable component method,the proposed method seeks to optimize both material and structure simultaneously by explicitly designing both macrostructure and representative volume element(RVE)-level *** exam-ples with transducer design requirements are provided to demonstrate the superiority of the SMMC method in comparison to traditional *** proposed method has broad impact in areas of integrated industrial manufacturing design:to solve for the optimized macro and microstructures under the objective function and constraints,to calculate the structural response efficiently using a reduced-order model:self-consistent analysis,and to link the SMMC method to manufacturing(industrial manufacturing or additive manufacturing)based on the design requirements and application areas.

关键词： Topology optimization Moving morphable component method Multiscale concurrent design reduced-order model

reduced model of Droop-controlled Converters for Transient Simulation Analysis

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Chinese Journal of Electrical Engineering 2022年第3期8卷 112-122页

作者： Yingjie Tan Yang Shen Min Xu Chao Shen Jinyong Lei Electric Power Research Institute CSGGuangzhou 510663China College of Electrical and Information Engineering Hunan UniversityChangsha 410082China

In recent years,the transient stability problems encountered by power grids have increasingly attracted interest due to the connection of renewable energy *** of the effective methods for studying the transient characteristics of a system is transient simulation *** reduce the simulation time,especially in a system with numerous renewable energy resources,model reduction has been widely ***,when a general reduced model is adopted to analyze different transient characteristics,a tradeoff between accuracy and simulation speed *** this study,reduced model selection is implemented to resolve this *** the droop-controlled converter as an example,this approach allows the transient simulation analysis of voltage,frequency,and power angle ***,a full-order model of the droop-controlled inverter is ***,the singular perturbation method is applied to derive different reduced-order ***,considering accuracy and simulation speed simultaneously,the most suitable reduced models for transient angle,voltage,and frequency simulation analyses are determined through time-domain simulation ***,the simulation results based on Matlab/Simulink are used to verify the correctness of the reduced model selection.

关键词： Droop-controlled inverter transient analysis reduced-order model singular perturbation

State-shared model for multiple-input multiple-output systems

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控制理论与应用（英文版） 2005年第4期3卷 348-356页

作者： Zhenhua TIAN Karlene A. HOO Deparmaent of Chemical Engineering Texas Tech University Lubbock TX USA

This work proposes a method to construct a state-shared model for multiple-input multiple-output （MIMO） systems. A state-shared model is defined as a linear time invariant state-space structure that is driven by measurement signals-the plant outputs and the manipulated variables, but shared by different multiple input/output models. The genesis of the state-shared model is based on a particular reduced non minimal realization. Any such realization necessarily fulfills the requirement that the output of the state-shared model is an asymptotically correct estimate of the output of the plant, if the process model is selected appropriately. The approach is demomtrated on a nonlinear MIMO system - a physiological model of calcium fluxes that controls muscle contraction and relaxation in human cardiac myocytes.

关键词： Adaptive identifier reduced-order model Multiple models Calcium fluxes Myocytes