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  • 1
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    Modeling and stability of segmented reflector telescopes - A decentralized approach (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The decentralization of a segmented reflector telescope based on a finite-element model of its structure is considered. The decentralization of the system at the panel level is considered. Each panel is originally treated as an isolated subsystem so that the controller design is performed independently at the local level, and then applied to the composite system for stability analysis. The panel-level control laws were designed by means of pole placement using local output feedback. Simulation results show a better 1000:1 vibration attenuation in panel position when compared to the open-loop system. It is shown that the overall closed-loop system is exponentially stable provided that certain conditions are met. The advantage to the decentralized approach is that the design is performed in terms of the low-dimensionality subsystems, thus drastically reducing the design computational complexities.
    Keywords: CYBERNETICS
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  • 2
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    Dynamic Modeling and Simulation Study for the Galileo Spacecraft Pulsed-Mode Spinup/400 N Main Engine Burn/Spindown Maneuvers (1996)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Description: Two Galileo dynamic models were developed to simulate the spinup/400-N main engine burn/spindown maneuvers for the critical events of Jupiter Orbit Insertion (JOI) and Perijove Raise Maneuver (PRM). The dynamic interaction among the spin thruster pulsing frequency science/magnetometer (SCI/MAG) boom flexible modes, and the propellant slosh modes were studied.
    Keywords: Astrodynamics
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  • 3
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    Galileo Mission to Jupiter (1996)
    In:  Other Sources
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    Publication Date: 2018-06-08
    Keywords: Lunar and Planetary Science and Exploration
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  • 4
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    Experimental study of robustness in adaptive control for large flexible structures (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An experimental study is performed to investigate the robustness of model reference adaptive control for the large flexible structures control application. The main nonidealities of concern are unmodeled dynamics, input saturation, and time delay effects (here, actuator and sensor dynamics are lumped into the last item for convenience). This study focuses on the robustness with respect to input saturation and time delay effects, since robustness to unmodeled dynamics is inherent to the basic algorithm and has been demonstrated experimentally elsewhere.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 90-3498 , AIAA Guidance, Navigation and Control Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
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  • 5
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    Adaptive control for flexible space structures with measurement noise (1987)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Simulation results are presented to address the problem of measurement noise in the design of adaptive controllers for large flexible space structures. In order to reduce the unrealistically high overall control demand resulting from the presence of leakage terms, a method has been developed for the introduction of noise filters into the adaptive controller while at the same time ensuring the global stability of the adaptive algorithm. A branch filter allows filtering of the output error without introducing phase lag into the adaptive loop. The technique is demonstrated in the simulation of an adaptive payload articulation control for a Space Station model.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: 1987 American Control Conference; Jun 10, 1987 - Jun 12, 1987; Minneapolis, MN; United States
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  • 6
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    Adaptive Control For Space-Station Joints (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Input gain weighting added to existing adaptive-control algorithm. Report discusses concept for adaptive control of rotations of various appended structures about joints on space station, with suppression of vibrations in both station and appendages. Concept relevant to such terrestrial applications as control of aircraft, suppression of vibrations in large buildings, and robotics.
    Keywords: ELECTRONIC SYSTEMS
    Type: NPO-17063 , NASA Tech Briefs (ISSN 0145-319X); 12; 6; P. 63
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  • 7
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    Adaptive Control For Flexible Structures (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Paper discusses ways to cope with measurement noise in adaptive control system for large, flexible structure in outer space. System generates control signals for torque and thrust actuators to turn all or parts of structure to desired orientations while suppressing torsional and other vibrations. Main result of paper is general theory for introduction of filters to suppress measurement noise while preserving stability.
    Keywords: ELECTRONIC SYSTEMS
    Type: NPO-17115 , NASA Tech Briefs (ISSN 0145-319X); 12; 2; P. 34
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  • 8
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    Control and Simulation of Space-Station Vibrations (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Adaptive control system reduces effects of model uncertainties. Report outlines method for finite-element dynamic analysis of space station. Purpose is to determine periods and modes of oscillation of structure and to analyze effect of proposed adaptive control system to damp out unwanted vibrations. With simplifications proposed, finite-element simulations performed during dynamic event, like docking of Space Shuttle, and used to control vibration-damping actuators.
    Keywords: MECHANICS
    Type: NPO-16852 , NASA Tech Briefs (ISSN 0145-319X); 11; 9; P. 87
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  • 9
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    Adaptive control experiment with a large flexible structure (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A large space antenna-like ground experiment structure has been developed for conducting research and validation of advanced control technology. A set of proof-of-concept adaptive control experiments for transient and initial deflection regulation with a small set of sensors and actuators were conducted. Very limited knowledge of the plant dynamics and its environment was used in the design of the adaptive controller so that performance could be demonstrated under conditions of gross underlying uncertainties. High performance has been observed under such stringent conditions. These experiments have established a baseline for future studies involving more complex hardware and environmental conditions, and utilizing additional sets of sensors and actuators.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 88-4153 , AIAA Guidance, Navigation and Control Conference; Aug 15, 1988 - Aug 17, 1988; Minneapolis, MN; United States
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  • 10
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    Dynamic modelling and simulation study for the Galileo spacecraft pulsed-mode spinup/400 N main engine burn/spindown maneuvers (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Two Galileo dynamic models were developed to simulate the spinup, the main engine burn and the spindown maneuvers for the critical events of the Jupiter orbit insertion and perijove raise maneuver. The dynamic interaction between the spin thruster pulsing frequency, the science magnetometer boom flexible modes and the propellant slosh modes were studied. The prediction of safe orbit insertion was validated in flight. For the perijove raise maneuver, the simulation results indicated that propellant unporting would occur if the original spin thruster duty cycle was not updated. Based on further simulation results, a new duty cycle was selected to prevent propellant unporting. Subsequent Galileo flight data indicated that the perijove raise maneuver was successfully executed.
    Keywords: Spacecraft Design, Testing and Performance
    Type: Paper SO96.5.07 , Proceedings of 4th International Symposium on Space Mission Operations and Ground Data Systems, volume 2; 2; 791-798; ESA-SP-394-Vol-2
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