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  • 1
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    Vibration isolation and suppression system for precision payloads in space (1999)
    Institute of Physics
    Details
    Publication Date: 1999-12-01
    Print ISSN: 0964-1726
    Electronic ISSN: 1361-665X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics
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    PAPER CURRENT
  • 2
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    Optical pathlength control in the nanometer regime on the JPL phase B interferometer testbed (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper describes experimental research being performed at the Jet Propulsion Laboratory to develop and validate control concepts arising out of NASA's Control Structure Interaction program. The facility is meant to be a ground testbed with relevance to a broad class of future precision optical space systems. The objective of the experimental program is to investigate a multi-layer control approach to the maintenance of nanometer level optical pathlength control in the presence of external disturbances and multiple structural resonances. A brief overview of the experimental facility is presented. The control design methodology is discussed, and several experimental results are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: In: Active and adaptive optical systems; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39451 15-74); p. 359-370.
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Selection of component modes for flexible multibody simulation (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 14; 278-286
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Multibody dynamics: Modeling component flexibility with fixed, free, loaded, constraint, and residual modes (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The assumed-modes method in multibody dynamics allows the elastic deformation of each component in the system to be approximated by a sum of products of spatial and temporal functions commonly known as modes and modal coordinates respectively. The choice of component modes used to model articulating and non-articulating flexible multibody systems is examined. Attention is directed toward three classical Component Mode Synthesis (CMS) methods whereby component normal modes are generated by treating the component interface (I/F) as either fixed, free, or loaded with mass and stiffness contributions from the remaining components. The fixed and free I/F normal modes are augmented by static shape functions termed constraint and residual modes respectively. A mode selection procedure is outlined whereby component modes are selected from the Craig-Bampton (fixed I/F plus constraint), MacNeal-Rubin (free I/F plus residual), or Benfield-Hruda (loaded I/F) mode sets in accordance with a modal ordering scheme derived from balance realization theory. The success of the approach is judged by comparing the actuator-to-sensor frequency response of the reduced order system with that of the full order system over the frequency range of interest. A finite element model of the Galileo spacecraft serves as an example in demonstrating the effectiveness of the proposed mode selection method.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 761-777
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Optical pathlength control on the JPL Phase B interferometer testbed (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Design and implementation of a controller for optical pathlength compensation on a flexible structure is presented. Nanometer level pathlength control is demonstrated in the laboratory. The experimental results are in close agreement with performance predictions.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Langley Research Center, The Fifth NASA(DOD Controls-Structures Interaction Technology Conference, Part 1; p 343-357
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Control-structure interaction in precision pointing servo loops (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The control-structure interaction problem is addressed via stability analysis of a generic linear servo loop model. With the plant described by the rigid body mode and a single elastic mode, structural flexibility is categorized into one of three types: (1) appendage, (2) in-the-loop minimum phase, and (3) in-the-loop nonminimum phase. Closing the loop with proportional-derivative (PD) control action and introducing sensor roll-off dynamics in the feedback path, stability conditions are obtained. Trade studies are conducted with modal frequency, modal participation, modal damping, loop bandwidth, and sensor bandwidth treated as free parameters. Results indicate that appendage modes are most likely to produce instability if they are near the sensor rolloff, whereas in-the-loop modes are most dangerous near the loop bandwidth. The main goal of this paper is to provide a fundamental understanding of the control-structure interaction problem so that it may benefit the design of complex spacecraft and pointing system servo loops. In this framework, the JPL Pathfinder gimbal pointer is considered as an example.
    Keywords: CYBERNETICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 12; 256-263
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Structural and Optical Pathlength Control Experiments on a Precision Truss (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: An experimental implementation of a nanometer level optical pathlength controller for long baseline space interferometry is presented. The pathlength compensation system is tested on a large precision truss structure and thus structural dynamics play a dominant role in the control system design.
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Optical pathlength control experiment on JPL phase B testbed (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An experimental implementation of a nanometer level optical pathlength control for large baseline space interferometry is presented. The pathlength compensation system is installed on a large flexible experimental truss, thus structural motions play a dominant role in the control system design. The associated control structure interaction problem is addressed to maintain the optical pathlength within the prescribed variation of 10-15 nanometer rms. By a successful blend of a structural control for damping augmentation and a direct pathlength control for the pathlength compensation, the optical pathlength variation has been maintained with 6 nanometer rms under the laboratory ambient disturbance and within 9 nanometer rms under a severe forced resonant disturbance.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 93-1695 , In: AIAA(ASME)ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pt. 6 (A93-33876 1; p. 3319-3327.
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Adaptive noncolocated velocity feedback for vibration damping (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method is proposed for adaptive noncolocated velocity feedback control of flexible structure vibrations. The approach, denoted as auto-tuning, is to drive the system into a sequence of controlled oscillations to provide accurate knowledge of the plant characteristics in the vicinity of the phase cross-over frequencies. An allpass phase notch filter cascade is used as the control architecture to phase stabilize each destabilizing mode in the plant transfer function. The allpass phase notch filter cascade is tuned precisely by the information extracted from the controlled oscillations.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 90-0659
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Reduced order component models for flexible multibody dynamics simulations (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Many flexible multibody dynamics simulation codes require some form of component description that properly characterizes the dynamic behavior of the system. A model reduction procedure for producing low order component models for flexible multibody simulation is described. Referred to as projection and assembly, the method is a Rayleigh-Ritz approach that uses partitions of the system modal matrix as component Ritz transformation matrices. It is shown that the projection and assembly method yields a reduced system model that preserves a specified set of the full order system modes. Unlike classical component mode synthesis methods, the exactness of the method described is obtained at the expense of having to compute the full order system modes. The paper provides a comprehensive description of the method, a proof of exactness, and numerical results demonstrating the method's effectiveness.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 90-0662
    Format: text
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