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MULTIPLE-INPUT, MULTIPLE-OUTPUT TIME-SERIES MODELS FROM SHORT DATA RECORDS

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1993年第3期16卷 549-556页

作者： HOLLKAMP, JJ USAF Wright Lab. Wright-Patterson AFB OH

An algorithm to estimate multiple-input, multiple-output, time-series models for structural system identification using short time histories is presented. The method uses order overspecification to reduce estimation bias and automatically sorts identified system modes from computational modes. The system natural frequencies, damping factors, mode shapes, and modal participation factors are estimated and can be used to reconstruct single-input, single-output models for every input-output pair. Experimental data from a large cantilevered flexible truss are used to demonstrate the technique. Modal estimates are comparable to those obtained using accepted methods such as the eigensystem realization algorithm.

关键词： Multiple Input, Multiple Output eigensystem realization algorithm Trusses System Identification Frequency Response Functions Observer Kalman Filter Identification FEM Aerospace Engineering Accelerometer Structural Dynamics

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FREQUENCY-WEIGHTED SYSTEM-IDENTIFICATION AND LINEAR QUADRATIC CONTROLLER-DESIGN

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1993年第2期16卷 330-336页

作者： HORTA, LG PHAN, M JUANG, JN LONGMAN, RW SULLA, JL LOCKHEED ENGN & SCI CO HAMPTONVA 23666

Application of filters for the frequency weighting of Markov parameters (pulse response functions) is described in relation to system/observer identification. The time domain identification approach recovers a model that has a pulse response weighted according to frequency. The identified model is composed of the original system and filters. The augmented system occurs in a form that can be used directly for frequency-weighted linear quadratic controller design. Data from either single or multiple experiments can be used to recover the Markov parameters. Measured acceleration signals from a truss structure are used for system identification and the model obtained is for frequency-weighted controller design. The procedure makes the identification and controller design complementary problems.

关键词： Linear Quadratic Regulator Trusses Frequency Response Functions Finite Element Modeling Spacecraft Dynamics Linear Quadratic Control Problem eigensystem realization algorithm Multiple Input Multiple Output Systems Aerospace Engineering Damping Ratio

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SPACECRAFT IN-ORBIT IDENTIFICATION USING eigensystem realization METHODS

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1992年第2期15卷 352-359页

作者： COOPER, JE WRIGHT, JR WRIGHT J R (Manchester Victoria University England)

In this paper two multi-input/multi-output state space methods suitable for the in-orbit system identification of space structures are considered. The ERA (eigensystem realization algorithm) method, which has already been used successfully on the Solar Array Flight Experiment, is compared with the ERA/DC (ERA using data correlations) method in terms of the formulation and computational effort. The methods are applied to simulated data from a space station type model. The ERA/DC method requires less model overspecification in the presence of noise than does the ERA method for similar quality of results. A revision of the ERA/DC method is suggested.

关键词： eigensystem realization algorithm Space Stations Large Space Structures State Space Representation Data Correlation Spacecraft Orbits Singular Value Decomposition Mathematical Models Single Input Single Output System Frequency Response Functions

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IDENTIFICATION, REDUCTION, AND REFINEMENT OF MODEL PARAMETERS BY THE eigensystem realization-algorithm

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1990年第6期13卷 1051-1059页

作者： YANG, CD YEH, FB TUNGHAI CHRISTIAN UNIV DEPT MATHTAICHUNGTAIWAN

A new identification scheme is developed to determine model parameters of vibrating structures from experimental data. The eigensystem realization algorithm, which forms the basis for a rational choice of model size determined by the singular values and accuracy indicators, is exploited and extended here to identify the mass, damping, and stiffness matrices directly from the singular value decomposition of the Hankel matrix. This approach provides a closed-loop identification framework that feeds back the output of eigensystem realization algorithm (ERA) and modifies the elements and the dimensions of the matrices accordingly by incorporating the model reduction and model refinement algorithm developed in this paper.

关键词： Stiffness Matrices eigensystem realization algorithm Singular Value Decomposition State Space Representation Second Order Differential Equations Structural Dynamics Flexible Structures Large Space Structures Mathematical Models Modal Analysis

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PRACTICAL ASPECTS OF ON-ORBIT MODAL IDENTIFICATION USING FREE-DECAY DATA

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JOURNAL OF SPACECRAFT AND ROCKETS 1992年第2期29卷 264-270页

作者： SCHENK, A PAPPA, RS NASA LANGLEY RES CTRSPACECRAFT DYNAM BRANCHHAMPTONVA 23665

This paper discusses practical aspects of performing on-orbit modal identification using time domain analysis of free-decay data. The effects of environmental constraints, structural characteristics, excitation, and sensing are reviewed. In a recent laboratory application, an on-orbit experiment is simulated using a limited number of excitation and measurement points. The identified modal parameters correlate well, though not uniquely, with those obtained in a complete modal survey. Practical difficulties in performing the correlation are illustrated.

关键词： Frequency Response Functions Space Station Freedom eigensystem realization algorithm Trusses Reaction Control System Data Acquisition Accelerometer Structural Response Control Moment Gyros Space Experiments

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INTEGRATED SYSTEM-IDENTIFICATION AND STATE ESTIMATION FOR CONTROL OF FLEXIBLE SPACE STRUCTURES

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1992年第1期15卷 88-95页

作者： CHEN, CW HUANG, JK PHAN, M JUANG, JN NASA LANGLEY RES CTRSPACECRAFT DYNAM BRANCHHAMPTONVA 23665

A novel approach is developed for identification of a state-space model and a Kalman filter gain from input and output data. There are four steps involved in this approach. First, the relation between a stochastic state-space model of a dynamical system and the coefficients of its autoregressive model with exogeneous input is derived. Second, an adaptive least-squares transversal predictor is used to estimate the coefficients of the model. Third, a state-space model and a steady-state Kalman filter gain of the dynamical system are then identified from the coefficients of the model by using the eigensystem realization algorithm. Fourth, a modal state estimator is constructed using the modal parameters of the identified model. On-line implementation of this algorithm can continually improve the modal parameters and the filter gain. It can also gradually update the system model when the system characteristics are slowly changing. Numerical examples are used to illustrate the feasibility of the new approach.

关键词： System Identification Space Structures Kalman Filter Gain eigensystem realization algorithm Autoregressive Model Adaptive Filter White Noise Singular Value Decomposition Flexible Structures NASA Langley Research Center

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COMPARISON OF 2 DISSIMILAR MODAL IDENTIFICATION TECHNIQUES

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1992年第4期15卷 840-846页

作者： PAPPA, RS SCHENK, A NIEDBAL, N KLUSOWSKI, E GERMAN AEROSP RES ESTAB INST AEROELASTICITYW-3400 GOTTINGENGERMANY

Recent laboratory results using a refined phase resonance method and the eigensystem realization algorithm on the same test structure are reported. These methods are dissimilar modal identification techniques suitable for future large spacecraft. The theory, application approach, and results obtained for each technique are summarized and compared. Although both methods worked well in this investigation, significant differences occurred in some identified mode shapes. Comparison of independently derived modal parameters provides the means for disclosing such discrepancies in flight projects.

关键词： eigensystem realization algorithm Cantilever Beam Structural Damping Accelerometer Data Analysis Singular Value Decomposition Structural Response Stiffness Matrices Data Acquisition Viscous Damping

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ROBUST MODAL IDENTIFICATION ESTIMATION OF THE MINI-MAST TESTBED

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1992年第3期15卷 642-647页

作者： ROEMER, MJ MOOK, DJ SUNY BUFFALO DEPT MECH & AEROSP ENGNBUFFALONY 14260

The Mini-Mast is a 20-m-long, three-dimensional, deployable/retractable truss structure designed to imitate future trusses in space. This structure has undergone various static and dynamic experiments to identify its modal properties so that control laws can be developed and tested. This paper presents results from a robust (with respect to measurement noise sensitivity), time-domain, modal identification technique for idenifying the modal properties of the Mini-Mast structure even in the presence of noisy measurements. Three testing/analysis procedures are considered: 1) sinusoidal excitation near the resonant frequencies of the Mini-Mast, 2) frequency response function averaging of several modal tests, and 3) random input excitation with a free response period. The results indicate that the robust technique of the paper is more accurate using the actual experimental data than are existing techniques.

关键词： Resonant Frequencies Frequency Response Functions Trusses eigensystem realization algorithm White Noise Vortices Finite Element Modeling Singular Value Decomposition Modal Analysis Kalman Filter

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SENSOR PLACEMENT FOR ON-ORBIT MODAL TESTING

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JOURNAL OF SPACECRAFT AND ROCKETS 1992年第2期29卷 239-247页

作者： LIM, TW Lockheed Engineering and Sciences Company Hampton Virginia 23666

A systematic procedure Of Placing sensors for the on-orbit modal identification of large flexible space structures is addressed. The concepts of system and component modal costs are introduced as a means of selecting target modes for modal testing. Assuming that a time-domain modal identification algorithm is employed to identify the modes from measured time response data, the sensors are placed to enhance the recovery of the target modes. As an application example of the procedure, an accelerometer placement study for the Space Station Freedom On-Orbit Modal Identification Experiment is presented.

关键词： Sensors Large Space Structures Accelerometer Space Station Freedom Finite Element Modeling Trusses Radiators eigensystem realization algorithm Reaction Control System Singular Value Decomposition

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RECURSIVE FORM OF THE eigensystem realization-algorithm FOR SYSTEM-IDENTIFICATION

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1989年第5期12卷 647-652页

作者： LONGMAN, RW JUANG, JN NASA LANGLEY RES CTRHAMPTONVA 23665

An algorithm is developed for recursively calculating the minimum realization of a linear system from sampled impulse response data. The Gram-Schmidt orthonormalization technique is used to generate an orthonormal basis for factorization of the data matrix. The system matrix thus identified is in upper Hessenberg form, which has advantages for the identification of modal parameters including damping coefficients, frequencies, mode shapes, and modal participation factors. It also has the property that once an element of the system matrix is computed, it is never altered as the dimension of the model is increased in the recursive process. Numerical examples are presented for comparison of the recursive and nonrecursive forms of the eigensystem realization algorithm.

关键词： eigensystem realization algorithm Linear Time Invariant System Damping Coefficient Singular Value Decomposition Flexible Structures Frequency Domain Ofeq

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