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  • 1
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    Modal model reduction or model reduction of large space structures in frequency domain (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Large space structures are characterized by a large number of modes, grouped frequencies, and small inherent damping. Model reduction techniques in time domain may not be effective due to small damping. The model truncation method is generally used. This method can not solve the problem of grouped frequencies, and will lose all the information about the higher order modes. A new method developed in this paper, which tries to minimize the error of interested transfer functions, makes use of all the information of the original system, and achieves improvement not only from a smaller error of transfer functions but also from better frequency distribution.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: JPL, Model Determination for Large Space Systems Workshop, Volume 2; p 800-826
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  • 2
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    The Qualification of a large electron irradiation facility for telecommunication satellite differential charging simulation (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The definition and procurement program is presented for the set up of a test simulating an electron environment on a model of a communication satellite to study the degradation of the thermal insulation materials during electron bombardment.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Lewis Res. Center Spacecraft Charging Technol., 1978; p 819-833
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  • 3
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    Effects of electron irradiation on large insulating surfaces used for European Communications Satellites (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Samples of aluminized Kapton used for passive thermal control on the VHF shield and the antenna dish of ESA's OTS satellite and its derivatives were subjected to an incident electron beam of 25 keV and irradiated for 8 hours at room temperature and at -173 C under a vacuum of the 10 to the minus 6 th power torr. Visual observations during electron irradiation, measurements of leakage current and discharge characteristics, and material degradation following completion of irradiation are discussed.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Lewis Res. Center Spacecraft Charging Technol., 1978; p 570-586
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  • 4
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    Issues in modeling and controlling the SCOLE configuration (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The parametric study of the in-plane Spacecraft Control Laboratory Experiment (SCOLE) system, the Floquet Stability Analysis, and three dimensional formulations of the SCOLE system dynamics are examined. Control issues are discussed, such as: control of large structures with delayed input in continuous time; control with delayed input in discrete time; control law design for SCOLE using Linear Quadratic Gaussian (LQC)/TRR technique; and optimal torque control for SCOLE slewing maneuvers.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Langley Research Center Proceedings of the 3rd Annual SCOLE Workshop; p 11-67
    Format: application/pdf
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  • 5
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    A time delay controller for magnetic bearings (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The control of systems with unknown dynamics and unpredictable disturbances has raised some challenging problems. This is particularly important when high system performance needs to be guaranteed at all times. Recently, the Time Delay Control has been suggested as an alternative control scheme. The proposed control system does not require an explicit plant model nor does it depend on the estimation of specific plant parameters. Rather, it combines adaptation with past observations to directly estimate the effect of the plant dynamics. A control law is formulated for a class of dynamic systems and a sufficient condition is presented for control systems stability. The derivation is based on the bounded input-bounded output stability approach using L sub infinity function norms. The control scheme is implemented on a five degrees of freedom high speed and high precision magnetic bearing. The control performance is evaluated using step responses, frequency responses, and disturbance rejection properties. The experimental data show an excellent control performance despite the system complexity.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA, Langley Research Center, Aerospace Applications of Magnetic Suspension Technology, Part 2; p 389-411
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  • 6
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    Interactive computer graphics and its role in control system design of large space structures (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: This paper attempts to show the relevance of interactive computer graphics in the design of control systems to maintain attitude and shape of large space structures to accomplish the required mission objectives. The typical phases of control system design, starting from the physical model such as modeling the dynamics, modal analysis, and control system design methodology are reviewed and the need of the interactive computer graphics is demonstrated. Typical constituent parts of large space structures such as free-free beams and free-free plates are used to demonstrate the complexity of the control system design and the effectiveness of the interactive computer graphics.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
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  • 7
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    Preliminary results of the dynamics and control of the SCOLE system (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Spacecraft Control Laboratory Experiment (SCOLE) system is assumed to be comprised of three main parts: the Space Shuttle Orbiter with its center of mass located at 0(sub 1); the mast, treated as a 130 ft long beam, connected to the Shuttle at 0(sub 2) and to the reflector at 0(sub 3); and the reflector, considered to be a flat plate with its center of mass at 0(sub 4). In the analysis given here, the angular momentum of the entire system is evaluated at point 0(sub 1) and the dynamics include the lateral displacements of the beam.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Langley Research Center, Spacecraft Control Laboratory Experiment (SCOLE) Workshop, 1984; p 158-215
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  • 8
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    Evaluation of performance characteristics for a space antenna system subjected to stochastic disturbances (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Control system synthesis for a large space antenna system is investigated based on stochastic linear optimal control techniques and the minimization of a quadratic Gaussian performance index. Parametric studies indicate that suitable combinations of plant and sensor noise characteristics, and state weighting matrices, can be found to meet the mission RMS pointing requirements. Using a combination of the Kalman filter and linear feedback, an optimal control law for the finite element model of the Hoop/Column structural system without damping is obtained. Removing the hoop-mounted actuator resulted in an increase in the RMS errors, an increased control effort, and an increase in the least damped modal time constant. Removing the hoop-mounted sensor resulted in an RMS error increase and estimator performance degradation, with less system RMS performance degradation than noted for removal of the hoop-mounted actuator.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
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  • 9
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    The dynamics and control of large flexible space structures X, part 1 (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The effect of delay in the control system input on the stability of a continuously acting controller which is designed without considering the delay is studied. The stability analysis of a second order plant is studied analytically and verified numerically. For this example it is found that the system becomes unstable for a delay which is equivalent to only 16 percent of its natural period of motion. It is also observed that even a small amount of natural damping in the system can increase the amount of delay that can be tolerated before the onset of instability. The delay problem is formulated in the discrete time domain and an analysis procedure suggested. The maximum principle from optimal control theory is applied to minimize the time required for the slewing of a general rigid spacecraft. The slewing motion need not be restricted to a single axis maneuver. The minimum slewing time is calculated based on a quasi-linearization algorithm for the resulting two point boundary value problem. Numerical examples based on the rigidized in-orbit model of the SCOLE also include the more general reflector line-of-sight slewing maneuvers.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-CR-181287 , NAS 1.26:181287
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  • 10
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    Electron irradiation tests on European meteorological satellite (1980)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: The observation of in orbit anomalies on Meteosat resulted in a test being performed to establish the charging and discharging characteristics of a flight configured engineering model when irradiated with electrons. Surface potentials were measured together with discharge rates and amplitudes. Results indicate that a large number of discharges are possible on the satellite whether or not the external surfaces are grounded. Initial measurements show that there are very high potential gradients around the satellite which obviously contribute largely to the discharging behavior. The time constant for charging is very small, indicating also that equilibrium conditions are achieved very quickly as the local ambient changes in orbit. A.R.H.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Lewis Research Center Spacecraft Charging Technol., 1980; p 835-855
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