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  • SPACECRAFT DESIGN, TESTING AND PERFORMANCE  (5)
  • STRUCTURAL MECHANICS  (1)
  • 1
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    Dynamics During Thrust Maneuvers of Flexible Spinning Satellites with Axial and Radial Booms (1986)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The dynamic response to operational maneuvers of spinning symmetric spacecraft with radial and axial booms was analyzed as part of the prelaunch dynamic analysis of the ISEE-3 spacecraft placed in a halo orbit around an Earth-Sun libration point, and later renamed ICE when it was directed to fly-by comet Giacobini-Zinner. The results presented use simple spacecraft models, and frequently give predictions that are good and easily obtained when the results from using a general purpose multibody dynamics program were very time consuming to obtain. Deployment of radial booms, spin-up after partial deployment, stationkeeping, and trajectory changes are analyzed. The latter two can involve both axial thrusting and pulsed radial thrusting once per revolution.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: ESA Proceedings of the Second International Symposium on Spacecraft Flight Dynamics; p 13-18
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Identifiability of conservative linear mechanical systems (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: With a sufficiently great number of sensors and actuators, any finite dimensional dynamic system is identifiable on the basis of input-output data. It is presently indicated that, for conservative nongyroscopic linear mechanical systems, the number of sensors and actuators required for identifiability is very large, where 'identifiability' is understood as a unique determination of the mass and stiffness matrices. The required number of sensors and actuators drops by a factor of two, given a relaxation of the identifiability criterion so that identification can fail only if the system parameters being identified lie in a set of measure zero. When the mass matrix is known a priori, this additional information does not significantly affect the requirements for guaranteed identifiability, though the number of parameters to be determined is reduced by a factor of two.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of the Astronautical Sciences (ISSN 0021-9142); 33; 95-118
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Research study: Space vehicle control systems (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: From the control point of view, spacecraft are classified into two main groups: those for which the spacecraft is fully defined before the control system is designed; and those for which the control system must be specified before certain interchangeable parts of a multi-purpose spacecraft are selected for future missions. Consideration is given to both classes of problems.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-161368
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    A definition of the degree of controllability - A criterion for actuator placement (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The unsolved problem of how to control the attitude and shape of future very large flexible satellite structures represents a challenging problem for modern control theory. One aspect of this problem is the question of how to choose the number and locations throughout the spacecraft of the control system actuators. Starting from basic physical considerations, this paper develops a concept of the degree of controllability of a control system, and then develops numerical methods to generate approximate values of the degree of controllability for any spacecraft. These results offer the control system designer a tool which allows him to rank the effectiveness of alternative actuator distributions, and hence to choose the actuator locations on a rational basis. The degree of controllability is shown to take a particularly simple form when the satellite dynamics equations are in modal form. Examples are provided to illustrate the use of the concept on a simple flexible spacecraft.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Dynamics and control of large flexible spacecraft; Jun 21, 1979 - Jun 23, 1979; Blacksburg, VA
    Format: text
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  • 5
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    Comparison of several system identification methods for flexible structures (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: In the last few years various methods of identifying structural dynamics models from modal testing data have appeared. This paper presents a comparison of four of these algorithms: the Eigensystem Realization Algorithm (ERA), the modified version ERA/DC where DC indicates that it makes use of data correlations, the Q-Markov Cover algorithm, and an algorithm due to Moonen, DeMoor, Vandenberghe and Vandewalle. The comparison is made using a five mode computer model of the 20 meter Mini-Mast truss structure at NASA Langley Research Center, and various noise levels are superimposed to produce simulated data. The results show that for the example considered ERA/DC generally gives the best results; that ERA/DC is always at least as good as ERA which is shown to be a special case of ERA/DC; that Q-Markov requires the use of significantly more data than ERA/DC to produce comparable results; and that in some situations Q-Markov cannot produce comparable results.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 91-0947 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; Apr 08, 1991 - Apr 10, 1991; Baltimore, MD; United States
    Format: text
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  • 6
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    Learning control for slewing of a flexible panel (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper studies the applicability of a discrete-time learning control method to the slewing control of a large flexible panel. Among the issues discussed are feasibility of the desired trajectories and their specification schemes, learning control by linear feedback, limitation of the actuator device output, and robustness to parameter changes or modeling errors associated with the chosen learning control design. To demonstrate the effectiveness of learning control, the system is designed with a proportional controller of the base angle only. Then application of the learning control is shown to make the system learn quickly to achieve the desired slewing without residual vibration at the end of the maneuver. Simulation results are reported and discussed.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: VPI&SU Symposium; May 08, 1989 - May 10, 1989; Blacksburg, VA; United States
    Format: text
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