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  • 1
    Electronic Resource
    Electronic Resource
    Nonlinear time-domain models of human controllers (1970)
    Springer
    Journal of optimization theory and applications 5 (1970), S. 23-38 
    Details
    ISSN: 1573-2878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Data from a compensatory tracking task are analyzed by using time-domain models. The linear time-domain results are transformed and compared with frequency-domain results. The nonlinear time-domain model of the same data reduced the remnant or residual power by only a small amount. The need for testing models on independent data is discussed. A novel, but attractive, method of generating functions for an efficient functional expansion of time-domain models is offered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928122
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    Paper (German National Licenses)
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  • 2
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    Nonlinear time-domain models of human controllers (1970)
    Springer
    Details
    Publication Date: 1970-01-01
    Print ISSN: 0022-3239
    Electronic ISSN: 1573-2878
    Topics: Mathematics
    Published by Springer
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    PAPER CURRENT
  • 3
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    A mathematical problem and a Spacecraft Control Laboratory Experiment (SCOLE) used to evaluate control laws for flexible spacecraft. NASA/IEEE design challenge (1984)
    In:  CASI
    Details
    Publication Date: 2004-12-04
    Description: Discussed here is a NASA program which was initiated to make direct comparisons of control laws for a mathematical problem. An experimental test item is being assembled under the cognizance of the Spacecraft Control Branch at Langley Research Center. The physical apparatus will consist of a softly supported dynamic model of an antenna attached to the Space Shuttle by a flexible beam. The control objective will include the task of directing the line of sight of the Shuttle/antenna configuration toward a fixed target, under conditions of noisy data, limited control authority, and random disturbances.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Spacecraft Control Laboratory Experiment (SCOLE) Workshop, 1984; p 1-27
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    On the use of maximum likelihood estimation for the assembly of Space Station Freedom (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Distributed parameter models of the Solar Array Flight Experiment, the Mini-MAST truss, and Space Station Freedom assembly are discussed. The distributed parameter approach takes advantage of (1) the relatively small number of model parameters associated with partial differential equation models of structural dynamics, (2) maximum-likelihood estimation using both prelaunch and on-orbit test data, (3) the inclusion of control system dynamics in the same equations, and (4) the incremental growth of the structural configurations. Maximum-likelihood parameter estimates for distributed parameter models were based on static compliance test results and frequency response measurements. Because the Space Station Freedom does not yet exist, the NASA Mini-MAST truss was used to test the procedure of modeling and parameter estimation. The resulting distributed parameter model of the Mini-MAST truss successfully demonstrated the approach taken. The computer program PDEMOD enables any configuration that can be represented by a network of flexible beam elements and rigid bodies to be remodeled.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: In: IEEE Conference on Decision and Control, 30th, Brighton, United Kingdom, Dec. 11-13, 1991, Proceedings. Vol. 3 (A93-13001 02-63); p. 2200-2205.
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Distributed parameter estimation for NASA Mini-Mast truss through displacement measurements (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Most methods of system identification of large flexible structures by far are based on the lumped parameter approach. Because of the considerable computational burden due to the large number of unknown parameters, distributed parameter approach, which greatly decreases the number of unknowns, has being investigated. In this paper a distributed parameter model for the estimation of modal characteristics of NASA Mini-Mast truss has been formulated. Both Bernoulli-Euler beam and Timoshenko beam equations are used to characterize the lateral bending vibrations of the truss. The measurement of the lateral displacement at the tip of the truss is provided to the maximum likelihood estimator. Closed-form solutions of the partial differential equations and closed-form expressions of the sensitivity functions are derived so that the estimation algorithm is highly efficient. The resulting estimates from test data by using Timoshenko beam model are found to be comparable to those derived from finite element analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: In: Structures sensing and control; Proceedings of the Meeting, Orlando, FL, Apr. 2, 3, 1991 (A93-22001 07-35); p. 266-277.
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Special class of nonlinear damping models in flexible space structures (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A special class of nonlinear damping models is investigated in which the damping force is proportional to the product of positive integer or the fractional power of the absolute values of displacement and velocity. For a one-degree-of-freedom system, the classical Krylov-Bogoliubov 'averaging' method is used, whereas for a distributed system, both an ad hoc perturbation technique and the finite difference method are employed to study the effects of nonlinear damping. The results are compared with linear viscous damping models. The amplitude decrement of free vibration for a single mode system with nonlinear models depends not only on the damping ratio but also on the initial amplitude, the time to measure the response, the frequency of the system, and the powers of displacement and velocity. For the distributed system, the action of nonlinear damping is found to reduce the energy of the system and to pass energy to lower modes.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 14; 77-83
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Software for continuum modeling of controls-structures interactions (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: It is clear that computer software is needed to assist in the generation of the equations of motion for complex, flexible spacecraft. Daniel Poelaert of ESTEC has developed the software DISTEL with which he has modeled the structural dynamics for different satellites. He is interested in expanding the capabilities of DISTEL to include structural damping and control systems. Unfortunately, the software has not been released. The author has developed similar software, PDEMOD, which has been used to model the Spacecraft control Laboratory Experiment (SCOLE), the Solar Array Flight Experiment (SAFE), the Mini-MAST truss, and the LACE satellite. PDEMOD has been used also for optimal parameter estimation and integrated control-structures design. PDEMOD is also being extended to include structural damping and control systems which are imbedded into the same equations for the structural dynamics. This paper will address the formulation of the equations for the structural dynamics of spacecraft structures which are constructed of a 3-dimensional arrangement of rigid bodies and flexible beam elements. Control system dynamics are imbedded into the same equations so that model order reduction approximations are not necessary. The input data consists of the physical data of the elements and the topological information describing how the elements are connected. PDEMOD accomplishes the following: (1) automatically assembles the equations of motion for the entire structural model; (2) calculates the modal frequencies; (3) calculates the mode shapes; (4) generates perspective views of the mode shapes; and (5) forms selected transfer functions. The software PDEMOD continues to be developed to provide additional features to assist in analyzing and synthesizing control and structural systems for flexible spacecraft.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA Workshop on Distributed Parameter Modeling and Control of Flexible Aerospace Systems; p 587-603
    Format: application/pdf
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  • 8
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    A piecewise continuous Timoshenko beam model for the dynamic analysis of tapered beam-like structures (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Distributed parameter modeling offers a viable alternative to the finite element approach for modeling large flexible space structures. The introduction of the transfer matrix method into the continuum modeling process provides a very useful tool to facilitate the distributed parameter model applied to some more complex configurations. A uniform Timoshenko beam model for the estimation of the dynamic properties of beam-like structures has given comparable results. But many aeronautical and aerospace structures are comprised of non-uniform sections or sectional properties, such as aircraft wings and satellite antennas. This paper proposes a piecewise continuous Timoshenko beam model which is used for the dynamic analysis of tapered beam-like structures. A tapered beam is divided into several segments of uniform beam elements. Instead of arbitrarily assumed shape functions used in finite element analysis, the closed-form solution of the Timoshenko beam equation is used. Application of the transfer matrix method relates all the elements as a whole. By corresponding boundary conditions and compatible conditions a characteristic equation for the global tapered beam has been developed, from which natural frequencies can be derived. A computer simulation is shown in this paper, and compared with the results obtained from the finite element analysis. While piecewise continuous Timoshenko beam model decreases the number of elements significantly; comparable results to the finite element method are obtained.
    Keywords: STRUCTURAL MECHANICS
    Type: North Carolina Agricultural and Technical State Univ., The Center for Aerospace Research: A NASA Center of Excellence at North Carolina Agricultural and Technical State University; 13 p
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  • 9
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    Likelihood estimation for distributed parameter models for NASA Mini-MAST truss (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A maximum likelihood estimation for distributed parameter models of large flexible structures was formulated. Distributed parameter models involve far fewer unknown parameters than independent modal characteristics or finite element models. The closed form solutions for the partial differential equations with corresponding boundary conditions were derived. The closed-form expressions of sensitivity functions led to highly efficient algorithms for analyzing ground or on-orbit test results. For an illustration of this approach, experimental data of the NASA Mini-MAST truss was used. The estimations of modal properties involve lateral bending modes and torsional modes. The results show that distributed parameter models are promising in the parameter estimation of large flexible structures.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Fourth NASA Workshop on Computational Control of Flexible Aerospace Systems, Part 2; p 881-90
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  • 10
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    A comparison of software for the modeling and control of flexible systems (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A researcher proposes a cooperative effort among specialists who use or develop software for simulating and analyzing the control of flexible aerospace systems. A comparison of existing software for modeling control systems and flexible structures, applied to several example problems would be quite valuable. The comparison would indicate computational efficiency and capabilities with respect to handling nonlinearities and graphical output. Because of the diversity of applications of such software, the researcher believes that the proposed cooperative effort can transcend projects involving specific applications. Comparisons of software capability and efficiency can be made and gaps can be identified. In this way the results of the cooperative effort can provide guidance for individual projects. Several charts which outline the objectives and approach of the proposed cooperative effort are given here.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Proceedings of the Workshop on Computational Aspects in the Control of Flexible Systems, Part 1; p 265-279
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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