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19th International Conference on System Theory, Control and Computing (ICSTCC)

作者： Ha, Jaehoon Kang, Byungmo Hong, Kilho Oh, Seungjong Agcy Def Dev Syst PMO 4 Daejeon South Korea

ISBN: (纸本)9781479984817

A ship borne launcher normally has a two-axes yaw-pitch gimbal configuration that can designate the target regardless of external disturbances, such as waves or wind. This kind of ship borne launcher is also called an inertially stabilized platform. Inertial stabilization is important in many aerospace and military applications, for example carrying out optical sensor functions, image processing, or target tracking. Various studies accordingly have been performed to achieve desired inertial stabilization performance. A ship borne launcher is a highly nonlinear system that cannot easily be expressed in an analytical form when considering nonlinearity elements. In particular, it is difficult to decouple the dynamic model of a ship borne launcher. In this case, an experimentally obtained dynamic model is more accurate than the analytically derived dynamic model. This paper proposes a method to simplify this nonlinear system through a system identification method, specifically, eigensystem realization algorithm (ERA).

关键词： ship borne launcher inertial stabilization nonlinear system system identification eigensystem realization algorithm

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Validation of a Discrete Vortex Method for Low Reynolds Number Unsteady Flows

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AIAA JOURNAL 2014年第3期52卷 643-649页

作者： Hammer, Patrick Altman, Aaron Eastep, Frank Univ Dayton Dayton OH 45469 USA

An in-house discrete vortex method code based on steady and unsteady thin airfoil theory is used to rapidly resolve the flowfield and force coefficients for low Reynolds number unsteady aerodynamic applications. The Uhlman method is incorporated due to its ability to incorporate vortex motion, and surface effects in the volume and surface integrals make it ideal to calculate the pressure and the associated forces on the airfoil surface. The code is then used to study both low and high angle of attack impulsive motions, the AIAA Fluid Dynamics Technical Committee Low Reynolds Number Working Group 0-45 deg Pitch-Ramp-Hold Canonical cases, a similar 0-85 deg Pitch-Ramp-Hold to closer simulate perching, a 0-40-0 deg Pitch-Ramp-Hold-Return, and high reduced frequency pure plunge. In all cases, the flowfield and accompanying lift-and-drag results compared well with experimental and computational fluid dymanics results given the extent of the assumptions underlying the discrete vortex method.

关键词： Freestream Velocity Vortex Structure Two Dimensional Flow Lift Coefficient Flow Visualization Thin Airfoil Theory CFD Flow Separation Power Spectral Density eigensystem realization algorithm

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A multi-reference-based mode selection approach for the implementation of NExT-ERA in modal-based damage detection

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STRUCTURAL CONTROL & HEALTH MONITORING 2014年第8期21卷 1137-1153页

作者： Mahmood, S. M. Faisal Haritos, Nicholas Gad, Emad Zhang, Lihai Univ Melbourne Dept Infrastruct Engn Parkville Vic 3010 Australia Swinburne Univ Technol Fac Engn & Ind Sci Hawthorn Vic 3122 Australia

A modal-based global method for identification, localization and quantification of damage of a shear frame structure is presented in this paper. The method involves identification of modal parameters from the vibration responses of the structure only (output only) using a combination of natural excitation technique (NExT) and eigensystem realization algorithm (ERA), and determination of stiffness parameters using very few identified modes by employing a least squares solution procedure. Finally, damage is indicated by comparing the stiffnesses of the (possibly) damaged structure with that of the undamaged structure. The implementation of NExT-ERA requires a reference channel for modal identification, but several limitations of using a single reference channel have been identified from the investigations of this study. To overcome the limitations, a new approach called multi-reference-based mode selection is proposed in this paper. The approach makes use of all the available DOFs, but one at a time, as reference channels and identifies the best representative modes of the structure by a mode screening process and a mode separation process. The approach is also automated for expediency and possible real-time application. The presented damage detection methodology is implemented on the analytical phase I and experimental phase II of the IASC-ASCE SHM benchmark problem and shows an accuracy of around 90% in damage detection. Copyright (C) 2014 John Wiley & Sons, Ltd.

关键词： modal identification damage detection natural excitation technique eigensystem realization algorithm multi-reference-based mode selection SHM benchmark problem

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algorithm 945: modred-A Parallelized Model Reduction Library

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ACM TRANSACTIONS ON MATHEMATICAL SOFTWARE 2014年第4期40卷 30-30页

作者： Belson, Brandt A. Tu, Jonathan H. Rowley, Clarence W. Univ Calif Berkeley Dept Elect Engn & Comp Sci Berkeley CA 94720 USA Princeton Univ Princeton NJ 08540 USA

We describe a new parallelized Python library for model reduction, modal analysis, and system identification of large systems and datasets. Our library, called modred, handles a wide range of problems and any data format. The modred library contains implementations of the Proper Orthogonal Decomposition (POD), balanced POD (BPOD) Petrov-Galerkin projection, and a more efficient variant of the Dynamic Mode Decomposition (DMD). The library contains two implementations of these algorithms, each with its own advantages. One is for smaller and simpler datasets, requires minimal knowledge to use, and follows a common matrix-based formulation. The second, for larger and more complicated datasets, preserves the abstraction of vectors as elements of a vector space and, as a result, allows the library to work with arbitrary data formats and eases distributed memory parallelization. We also include implementations of the eigensystem realization algorithm (ERA), and Observer/Kalman Filter Identification (OKID). These methods are typically not computationally demanding and are not parallelized. The library is designed to be easy to use, with an object-oriented design, and includes comprehensive automated tests. In almost all cases, parallelization is done internally so that scripts that use the parallelized classes can be run in serial or in parallel without any modifications.

关键词： algorithms Experimentation Performance Model reduction system identification Python Proper Orthogonal Decomposition Balanced Proper Orthogonal Decomposition Dynamic Mode Decomposition Koopman modes Observer/Kalman Filter Identification eigensystem realization algorithm

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Investigation of the Aerodynamic Analysis of Super Long-Span Bridges by Using ERA-Based Reduced-Order Models

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JOURNAL OF BRIDGE ENGINEERING 2014年第9期19卷 04014033-04014033页

作者： Ebrahimnejad, L. Janoyan, K. D. Valentine, D. T. Marzocca, P. AECOM Boston MA 02110 USA Clarkson Univ Dept Civil & Environm Engn Potsdam NY 13699 USA Clarkson Univ Dept Mech & Aeronaut Engn Potsdam NY 13699 USA

Reduced-order models (ROM) are computationally efficient techniques, which have been used widely for predicting unsteady aerodynamic response of airfoils and wings. However, they have not been applied extensively to perform unsteady fluid dynamic analysis of super long-span bridges. This paper discusses the application of a reduced-order computational fluid dynamics (CFD) model based on the eigensystem realization algorithm (ERA) in the aerodynamic analysis of three well-studied long-span bridges. The aerodynamic impulse responses of the Great Belt Bridge (GBB) and Stonecutters and Messina Strait Bridges were used to construct the aerodynamic ROM, and then the aerodynamic forces due to arbitrary inputs and their corresponding flutter derivatives were evaluated and compared to those of the model coupled with an advanced CFD code. Results demonstrate reasonable prediction power and high computational efficiency of the technique that can serve for preliminary design, optimization, and control purposes. The methodology described in this paper has wide application in many civil engineering problems where flexible structures interact with unsteady fluid mechanical phenomena. (C) 2014 American Society of Civil Engineers.

关键词： Computational fluid dynamics Reduced-order models eigensystem realization algorithm Long-span bridges Aerodynamic analysis

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Efficient Computation of Unsteady Aerodynamic Loads Using Computational-Fluid-Dynamics Linearized Methods

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JOURNAL OF AIRCRAFT 2013年第2期50卷 425-440页

作者： Fleischer, Dietmar Breitsamter, Christian Tech Univ Munich Inst Aerodynam & Fluid Mech D-85747 Garching Germany

In the present work, generalized aerodynamic forces concerning the time and frequency domains are analyzed. Thereby, the transonic flow regime is of main interest. For this purpose, the low-frequency structural modes of the AGARD 445.6 wing and a wing-fuselage configuration known as the fuselage cropped delta wing are used to compute the corresponding generalized aerodynamic forces with the Euler methods AER-Eu (nonlinear, time domain) and AER-SDEu (linear, frequency domain). Furthermore, a reduced-order model based on the AER-Eu solver is generated as a linear state-space model for fast computations of generalized aerodynamic forces in the discrete time domain. This is realized by recording the responses of the AER-Eu solver to a set of orthogonal step functions. The resulting time series are further processed to extract the impulse responses required for the system identification with the eigensystem-realization algorithm. The transfer of the time domain results into frequency domain is achieved via the Fourier analysis of the time series of the harmonic responses and the extracted impulse responses for modal movement of the body. It is shown that the linear state-space reduced-order model based on appropriate computational-fluid-dynamics conditioning is an efficient way for the computation of generalized aerodynamic forces required in linear aeroelastic analysis.

关键词： Aerodynamic Force Vector Total Variation Diminishing eigensystem realization algorithm Frequency Domain Linear Time Invariant Harmonic Oscillation Transonic Flow Fuselage Configurations Euler Method Mean Aerodynamic Chord

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Wireless sensor integration for bridge model health monitoring

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JOURNAL OF VIBROENGINEERING 2013年第2期15卷 1028-1040页

作者： Liu, Chengyin He, Xianyin Shenzhen Grad Sch Harbin Inst Technol Shenzhen 518055 Peoples R China

An integrated hardware and software system for a scalable wireless sensor network (WSN) is designed and developed for structural health monitoring. An extension sensor board is designed, developed, and calibrated to meet the requirements for structural vibration monitoring and modal identification. The extension sensor board has 3 axes of accelerometers in three directions and a temperature sensor. Software components have been implemented within the TinyOS operating system to provide a flexible software platform and scalable performance for structural health monitoring applications. The prototype WSN is deployed on a reduced-scale bridge model with 3 nodes in a single-hop network for performing dynamic monitoring civil engineering structures. Two output-only time-domain system identification methods are employed namely, the Frequency Domain Decomposition (FDD) method and the Natural Excitation Technique (NExT) combined with the eigensystem realization algorithm (ERA). Testing results show that the WSN provides accurate vibration data for identifying vibration modes of a bridge.

关键词： wireless sensor network structural health monitoring frequency domain decomposition natural excitation technique eigensystem realization algorithm

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Covariance-Based realization algorithm for the Identification of Aeroelastic Dynamics

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2012年第4期35卷 1169-1177页

作者： Miller, Daniel N. de Callafon, Raymond A. Brenner, Martin J. Univ Calif San Diego Dept Mech & Aerosp Engn La Jolla CA 92093 USA NASA Dryden Flight Res Ctr Edwards AFB CA 93523 USA

A novel subspace system identification method based on covariance estimates and inspired by classical realization techniques is presented that constructs system estimates from measured input output data. The resulting algorithm allows for the identification of parametric system models from data sets of large signal dimension and is applicable to data perturbed by colored noise and acquired in closed-loop operation due to the unbiased estimation of cross-covariance functions, even in low signal-to-noise conditions. The algorithm is applied to data measured onboard an F/A-18. The results demonstrate the effectiveness of the algorithm in efficiently computing accurate, unbiased linear dynamic models from large data sets of high-dimensional signal sets obtained from aircraft in flight.

关键词： Linear Time Invariant System Computing Ailerons Accelerometer eigensystem realization algorithm Singular Value Decomposition Leading Edge Flap Pressure Sensors White Noise Aircraft Structures

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Decentralized NExT/ERA and RDT/ERA system identification in wireless smart sensor networks

Decentralized NExT/ERA and RDT/ERA system identification in ...

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International Conference on Civil, Architectural and Hydraulic Engineering (ICCAHE 2012)

作者： Cui, Dingyu Xin, Kegui Spencer, B. F., Jr. Liu, Yufei Tsinghua Univ Dept Civil Engn Beijing 100084 Peoples R China UIUC Dept Civil & Environm Engn Urbana IL 61800 USA

ISBN: (纸本)9783037854846

Wireless smart sensor networks (WSSN) have many advances compared with traditional structural health monitoring (SHIM) such as wireless process, real-time calculation and low cost. However power consumption is considered as one of the most limitations in this field. The unique features offered by decentralized data aggregation (DDA) technique with the potential to overcome power consumption enable implementation of the dense array of WSSN on large structures. This paper presents a system identification of a simply supported plate based on the random decrement technique (RDT) and natural excitation technique (NExT) in combination with eigensystem realization algorithm (ERA) using Illinois Structural Health Monitoring Project (ISHMP) Services Toolsuite. Finally the system parameters including natural frequency and mode shapes are in accordance with numerical simulation showing efficacy and feasibility of decentralized NExT/ERA and RDT/ERA system identification.

关键词： Natural excitation technique Random decrement technique eigensystem realization algorithm Wireless smart sensors Decentralized data aggregation

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Study of Modal Parameter Identification from Ambient Vibration on a Deep Radial Gate

Study of Modal Parameter Identification from Ambient Vibrati...

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International Conference on Vibration, Structural Engineering and Measurement (ICVSEM 2011)

作者： Cai, Yuan Qi Zhang, Ke Wuhan Univ Sch Civil Engn Wuhan 430072 Peoples R China

ISBN: (纸本)9783037852644

In the engineering background of the prototype test of a deep radial gate on three gorges dam, two methods are provided for the modal parameter identification of the radial gate, one is applying operation modal analysis (OMA) to a gate which is under flood discharge, the other one is applying experiment modal analysis (EMA) to a inactive gate with some other gates under flood discharge. This paper is based on the feasibility study on the former method. We use the natural excitation technology (NExT) combined with the eigensystem realization algorithm (ERA) to determine the dynamic characteristics of a gate. Displacement data at 7 locations were processed using NExT-ERA to extract the natural frequency and associated damping ratio. The results show the effectiveness of this modal identification methodology and the possibility of implementing it on other hydraulic structure.

关键词： Ambient vibration Three Gorges Project Radial gate Modal parameter identification eigensystem realization algorithm

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