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MODAL IDENTIFICATION OF GYROSCOPIC DISTRIBUTED-PARAMETER SYSTEMS

AIAA JOURNAL 1990年第12期28卷 2104-2109页

作者： NORRIS, MA SILVERBERG, L VIRGINIA POLYTECH INST & STATE UNIV ENGN SCI & MECHBLACKSBURGVA 24061 N CAROLINA STATE UNIV MISS RES CTRRALEIGHNC 27695

A new modal identification method for gyroscopic distributed-parameter systems is presented. The method represents an extension of previous work for the class of self-adjoint distributed-parameter systems. The modal identification method is formulated as a variational problem in which stationary values of a functional quotient are sought. The computation of the functional quotient is carried out using a set of admissible functions defined over the spatial domain of the system. As an illustration, the modal identification of a whirling shaft undergoing bending vibration is carried out and the effectiveness of the method is verified.

关键词： Distributed Parameter System Rotating Unbalance eigensystem realization algorithm Stiffness Matrices Singular Value Decomposition Numerical Simulation Synchronous Precession Dirac Delta Function Helicopter Blade Satellites

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System identification in the presence of completely unknown periodic disturbances

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2000年第2期23卷 251-259页

作者： Goodzeit, NE Phan, MQ Princeton Univ Dept Mech & Aerosp Engn Princeton NJ 08544 USA

A system identification method to extract the disturbance-free dynamics and the disturbance effect correctly despite the presence of unknown periodic disturbances is presented. The disturbance frequencies and waveforms can be completely unknown and arbitrary Only measurements of the excitation input and the disturbance-contaminated response are used for identification. Initially, the disturbances are modeled implicitly. When the order of an assumed input-output model exceeds a certain minimum value, the disturbance information is completely absorbed in the identified model coefficients. A special interaction matrix explains the mechanism by which information about the system and the disturbances are intertwined and more importantly, how they can be separated uniquely and exactly for later use in identification and control. From the identified information a feedforward controller can be developed to reject the unwanted disturbances without requiring the measurement of a separate disturbance-correlated signal. The multi-input multi-output formulation is first derived in the deterministic setting for which the system and disturbance identification is exact. Extensions to handle noise-contaminated data are also provided. Experimental results illustrate the method on a flexible structure. A companion paper addresses the problem where the disturbance effect is modeled explicitly.

关键词： System Identification Lightly Damped Structures Trusses eigensystem realization algorithm Singular Value Decomposition Neural Networks Feedback Control Accelerometer White Noise

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IDENTIFYING APPROXIMATE LINEAR-MODELS FOR SIMPLE NONLINEAR-SYSTEMS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1986年第4期9卷 385-390页

作者： HORTA, LG JUANG, JN Struct. Dyn. Branch NASA Langley Res. Cent. Hampton VA USA

This paper addresses the identification (realization) of approximate linear models from response data for certain nonlinear dynamic systems. Response characteristics for several typical nonlinear joints are analyzed mathematically and represented by series expansions. The parameters of the series expansion are then compared with the modal parameters of a linear model identified by the eigensystem realization algorithm. The agreement of the identified model and the analytically derived representation is excellent for the cases studied. Also, laboratory data from a model exhibiting stiffening behavior was analyzed using the eigensystem realization algorithm and fast Fourier transform.

关键词： Nonlinear Systems eigensystem realization algorithm Structural System Singular Value Decomposition Rigid Body Kinematics Numerical Integration Transient Response Bending Stiffness Frequency Domain Accelerometer

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Dynamic system characterization via Eigenvalue orbits

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1999年第3期22卷 447-454页

作者： Marczyk, J Rodellar, J Barbat, AH Tech Univ Catalonia Sch Civil Engn Dept Struct Mech Barcelona Spain Tech Univ Catalonia Sch Civil Engn Dept Appl Math 3 Barcelona Spain

A new model-free approach for the description of general dynamical systems with unknown structure, order, and excitation is introduced. The approach is based on the new concept of eigenvalue orbit, The eigenorbits are obtained by building an associated linear time-variant system through a matrix that relates the output measurements in a moving horizon window and viewing the trajectories of its time-varying eigenvalues. How the eigenorbits may be computed from the measurements and used for the characterization of the original system is shown. The basic properties of the eigenorbits are presented via a series of theorems for the case of a discrete-time, linear time-invariant system. A set of examples are included to illustrate these properties for more general classes of systems and to suggest some practical issues that can be drawn from the orbits.

关键词： Eigenvalues Linear Time Invariant Mathematical Models eigensystem realization algorithm Singular Value Decomposition Aspect Ratio Four Degree of Freedom Orbit Determination Dissipative System Neural Networks

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Modal parameter identification of controlled structures

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1997年第1期20卷 184-186页

作者： Kasai, T Komatsu, K Sano, M National Aerospace Laboratory Chofu Tokyo 182 Japan

The simple numerical procedure presented for extracting the modal parameters of a closed-loop structural system is formulated via the extended Kalman Filter (EKF) technique. The unknown parameters encompass eigenfrequencies, damping ratios, mode shapes, and modal masses; the initial values required by the EKF formulation are furnished by FEM preanalysis. The modal model is easily modified by experimental results in virtue of the FEM-experimental modal analysis commonality. (AIAA)

关键词： Linear Quadratic Regulator Vibration Suppression Pilot Angle of Attack Control Surfaces Structural System Experimental Aircraft Aeronautical Industry Development Center eigensystem realization algorithm Digital Flight Control System

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Time-domain identification of low-order models for flexible structures

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1999年第6期22卷 908-909页

作者： Bauer, RJ Hughes, PC Dalhousie Univ Halifax NS B3J 1Z1 Canada Univ Toronto Inst Aerosp Studies Toronto ON M3H 5T6 Canada

Consideration is given to a novel approach to system identification that applies cubic smoothing splines to the system Markov parameters calculated by Observer Kalman Filter Identification. Applying this smoothing procedure early in the identification process allows models that are both low order and accurate to be directly identified. Experiments with Daisy, a flexible spacecraft emulator, demonstrate significant computational savings and numerical robustness by avoiding the model overspecification and reduction process. (AIAA)

关键词： Flexible Structures eigensystem realization algorithm Model Order Reduction Reaction Wheels Control System Design Space Structures Satellites Yaw

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Global-local observer Markov parameter identification for system realization

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1996年第6期19卷 1221-1225页

作者： Papadopoulos, M Garcia, E Tolson, RH GEORGE WASHINGTON UNIV DEPT CIVIL MECH & ENVIRONM ENGNJOINT INST ADVANCEMENT FLIGHT & SCIHAMPTONVA 23681 NASA LANGLEY RES CTRHAMPTONVA 23681

The observer/Kalman filter identification method uses general input/output data to compute the Markov parameters of an asymptotically stable observer. A state space realization is subsequently obtained from these estimated Merkov parameters. However, numerical ill-conditioning, data acquisition, and computer memory constraints may Limit the number of measurements that can be processed far Markov parameter estimation. Use of Limited measurements then will reduce spatial information. A global-local version of the observer/Kalman filter identification was therefore developed to overcome this dilemma. This method obtains a local state space realization from a reduced set of measurements. A global state space realization is subsequently obtained from a least squares process on the remaining measurements. A six-degree-of-freedom numerical simulation and experimental data from a frame structure are presented to validate the proposed method.

关键词： Observer Kalman Filter Identification Data Acquisition System Six Degree of Freedom Numerical Simulation Computer Memory eigensystem realization algorithm Frequency Response Functions Stiffness Matrices Data Correlation State Space Representation

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Optimal sensor placement for modal identification using system-realization methods

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1996年第3期19卷 729-731页

作者： Kammer, DC University of Wisconsin-Madison Madison Wisconsin 53706-1691

For a typical modern ground vibration test, a large number of sensors is usually available to the test engineer. There are, however, currently important modal identification problems in which the number of available sensors is very limited, and their positions are essentially fixed once in service. Here, the Effective Independence (EfI) sensor placement method proposed by Kammer (1991) is considered. The EfI method maximizes both the spatial independence and signal strength of the targeted finite element model mode shapes, partitioned to the corresponding sensor locations, by maximizing the determinant of an associated Fisher information matrix. Although the EfI method has been shown to place sensors to the benefit of posttest correlation and model updating, it is not clear that the method enhances the modal identification process itself. This study presents the formal relationship between the EfI sensor placement technique and system-realization methods of modal identification. A currently popular system-realization method, called the eigensystem realization algorithm (Juang and Pappa, 1985), is considered. (AIAA)

关键词： Sensors Finite Element Modeling eigensystem realization algorithm Output Feedback Singular Value Decomposition Flexible Structures Structural System Accelerometer Robust Control Astronautics

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Removing bias from discrete time models based on finite interval response data

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1996年第6期19卷 1216-1220页

作者： Baker, ML Mingori, DL California Univ. Los Angeles

Modern off-line system identification methods necessarily form a system realization using a finite amount of data The models constructed are usually of an order smaller than the actual order of the physical system because it is not practical to model the relatively unimportant states. A method is presented to improve the selection of the important states and the model order in system identification methods based on generalized Hankel matrices. When forming a reduced-order model, it is critical to be able to accurately identify the important states and to select the appropriate model order. Some currently popular methods implicitly contain a frequency weighting that comes from the use of a finite time interval of data in the identification. A method is presented to remove this implicit bias, and excellent results are obtained, even when the response data used span only a fraction of a cycle of the dominant frequency.

关键词： Observability Gramian eigensystem realization algorithm Stiffness Matrices Singular Value Decomposition Second Order Differential Equations Material Properties State Space Systems Viscous Damping

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Aeroelastic dynamic analysis of a full F-16 configuration for various flight conditions

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AIAA JOURNAL 2003年第3期41卷 363-371页

作者： Geuzaine, P Brown, G Harris, C Farhat, C Univ Colorado Dept Aerosp Engn Sci Ctr Aerosp Struct Boulder CO 80309 USA

An overview is given of recent advances in a three-field methodology for modeling and solving nonlinear fluid-structure interaction problems, and its application to the prediction of the aeroelastic frequencies and damping coefficients of a full F-16 configuration in various subsonic, transonic, and supersonic airstreams is reported. In this three-field methodology the How is described by the arbitrary Lagrangian-Eulerian form of the Enter equations, the structure is represented by a detailed finite element model, and the fluid mesh is unstructured, dynamic, and updated by a robust torsional spring analogy method. Simulation results are presented for stabilized, accelerated, low-g, and high-g flight conditions, and correlated with flight-test data. Consequently, the practical feasibility and potential of the described computational-fluid-dynamics-based computational method for the flutter analysis of high-performance aircraft, particularly in the transonic regime, are discussed.

关键词： Arbitrary Lagrangian Eulerian Computational Methods Euler Equations Dynamic Analysis High Performance Aircraft Freestream Mach Number Angle of Attack eigensystem realization algorithm Transonic Wind Tunnel Energy Transfer

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