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  • 1
    Publication Date: 2018-06-08
    Description: The controller development and the tracking performance evaluation for NASA's Deep Space Network antenna are presented. A trajectory preprocessor, LQG (Linear Quadratic Gaussian) controller, feedforward controller, and their combination are designed, built, analyzed, and tested.
    Keywords: Communications and Radar
    Format: text
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  • 2
    Publication Date: 2018-06-08
    Description: The control systems of the NASA 70-m antennas include the antenna control system, the Master Equatorial control system, and their combinations (called nodes).
    Keywords: Communications and Radar
    Type: AIAA Conference on Guidance Navigation and Control; San Antonio, TX; United States
    Format: text
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  • 3
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    In:  Other Sources
    Publication Date: 2018-06-08
    Type: NATO Advanced Study Institute; Brussels; Belgium
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  • 4
    Publication Date: 2019-01-25
    Description: Two approaches to the problem of model reduction for flexible spacecraft that have proved very useful are balancing and model truncation. Furthermore, it is well known that a model representation of a lightly damped flexible structure with widely spaced natural frequencies is approximately balanced. Consequently, reduction in either coordinate system gives similar results for this case. It is important to note, however, that flexible space structures typically have clusters of closely spaced frequencies. In such cases, reduction in model coordinates can give large errors, while the error obtained using balancing is generally much smaller. A new reduction procedure which combines the best features of model and balanced reduction is therefore developed. It is more efficient than balanced reduction of the full system, as it only involves balancing those subsystems of close modes that are highly correlated, yet is shown to yield results which are essentially as good.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Proceedings of the 3rd Annual Conference on Aerospace Computational Control, Volume 2; p 620
    Format: text
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  • 5
    Publication Date: 2019-06-28
    Description: The controller development and the tracking performance evaluation for the DSS-13 antenna are presented. A trajectory preprocessor, linear quadratic Gaussian (LQG) controller, feedforward controller, and their combination were designed, built, analyzed, and tested. The antenna exhibits nonlinear behavior when the input to the antenna and/or the derivative of this input exceeds the imposed limits; for slewing and acquisition commands, these limits are typically violated. A trajectory preprocessor was designed to ensure that the antenna behaves linearly, just to prevent nonlinear limit cycling. The estimator model for the LQG controller was identified from the data obtained from the field test. Based on an LQG balanced representation, a reduced-order LQG controller was obtained. The feedforward controller and the combination of the LQG and feedforward controller were also investigated. The performance of the controllers was evaluated with the tracking errors (due to following a trajectory) and the disturbance errors (due to the disturbances acting on the antenna). The LQG controller has good disturbance rejection properties and satisfactory tracking errors. The feedforward controller has small tracking errors but poor disturbance rejection properties. The combined LQG and feedforward controller exhibits small tracking errors as well as good disturbance rejection properties. However, the cost for this performance is the complexity of the controller.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 37-55
    Format: application/pdf
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  • 6
    Publication Date: 2019-06-28
    Description: Accurate information about wind action on antennas is required for reliable prediction of antenna pointing errors in windy weather and for the design of an antenna controller with wind disturbance rejection properties. The wind tunnel data obtained 3 years ago using a scaled antenna model serves as an antenna industry standard, frequently used for the first purpose. The accuracy of the wind tunnel data has often been challenged, since they have not yet been tested in a field environment (full-aized antenna, real wind, actual terrain, etc.). The purpose of this investigation was to obtain selected field measurements and compare them with the available wind tunnel data. For this purpose, wind steady-state torques of the DSS-13 antenna were measured, and dimensionless wind torque coefficients were obtained for a variety of yaw and elevation angles. The results showed that the differences between the wind tunnel torque coefficients and the field torque coefficients were less than 10 percent of their values. The wind-gusting action on the antenna was characterized by the power spectra of the antenna encoder and the antenna torques. The spectra showed that wind gusting primarily affects the antenna principal modes.
    Keywords: AERODYNAMICS
    Type: The Telecommunications and Data Acquisition Report; p 210-220
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  • 7
    Publication Date: 2018-06-08
    Description: This paper describes some of the recent upgrades in the antenna structure, control system, and instruments that improve its pointing accuracy.
    Keywords: Communications and Radar
    Type: 8th IEEE International Conference on Methods & Models in Automation and Robotics; Szczecin; Poland
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  • 8
    Publication Date: 2019-06-28
    Description: Upcoming NASA missions will require tracking of low-orbit satellites. As a consequence, NASA antennas will be required to track satellites at higher rates than for the current deep space missions. This article investigates servo design issues for the 34-m beam-waveguide antennas that track low-orbit satellites. This includes upgrading the servo with a feedforward loop, using a monopulse controller design, and reducing tracking errors through either proper choice of elevation pinion location, application of a notch filter, or adjustment of the elevation drive amplifier gain. Finally, improvement of the signal-to-noise ratio through averaging of the over-sampled monopulse signal is described.
    Keywords: MECHANICAL ENGINEERING
    Type: The Telecommunications and Data Acquisition Report; p 135-152
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  • 9
    Publication Date: 2019-06-28
    Description: This work is the first step toward increasing the bandwidth of the DSS-13 antenna position loop controller. A wider bandwidth of the controller allows for faster tracking rates and better pointing performance under windy conditions. To achieve this goal, the antenna control system model has to be improved, such that it will accurately reflect the dynamic properties of the antenna. The existing analytical model, due to its many uncertainties, could not be used in the design of the controller. However, by using experimental data, the analytical model is modified and improved, and a new model is obtained through system identification techniques.
    Keywords: MECHANICAL ENGINEERING
    Type: The Telecommunications and Data Acquisition Report; p 42-53
    Format: application/pdf
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  • 10
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    In:  Other Sources
    Publication Date: 2018-06-08
    Description: In this work we describe the impact of actuators and sensors gains and locations of structural properties, which includes structural controllability and observability, and structural and modal norms.
    Keywords: Structural Mechanics
    Type: NATO Advanced Study Institute; Brussels; Belgium
    Format: text
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