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  • 1
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    On the conflict frequency at air route intersections (1977)
    Elsevier
    Details
    Publication Date: 1977-10-01
    Print ISSN: 0041-1647
    Electronic ISSN: 1878-3821
    Topics: Architecture, Civil Engineering, Surveying
    Published by Elsevier
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    PAPER CURRENT
  • 2
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    Integrated structure/control law design by multilevel optimization (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: CYBERNETICS
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 14; 1001-100
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Flexible aircraft dynamic modeling for dynamic analysis and control synthesis (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The linearization and simplification of a nonlinear, literal model for flexible aircraft is highlighted. Areas of model fidelity that are critical if the model is to be used for control system synthesis are developed and several simplification techniques that can deliver the necessary model fidelity are discussed. These techniques include both numerical and analytical approaches. An analytical approach, based on first-order sensitivity theory is shown to lead not only to excellent numerical results, but also to closed-form analytical expressions for key system dynamic properties such as the pole/zero factors of the vehicle transfer-function matrix. The analytical results are expressed in terms of vehicle mass properties, vibrational characteristics, and rigid-body and aeroelastic stability derivatives, thus leading to the underlying causes for critical dynamic characteristics.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Langley Research Center, Proceedings of the Workshop on Computational Aspects in the Control of Flexible Systems, Part 2; p 709-743
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Effect of Aeropropulsive Interactions and Design Sensitivities on Optimal Hypersonic Ascent Trajectories (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In this paper, trajectory optimization is used as a tool to better understand the performance characteristics of hypersonic Single-Stage-To-Orbit(SSTO) vehicle exhibiting significant aeropropulsive interactions. The energy state approximation is used to determine a straightforward method of determining the scramjet-powered phase of the mission. The energy state method is then used to generate fuel-optimal trajectory results over this portion of the mission for a vehicle configuration of this class. The fuel-optimal unconstrained trajectory is marked by low-altitude acceleration, while a dynamic pressure-constrained trajectory is seen to ride the dynamic pressure constraint for the entire scramjet mission phase. The significance of aeropropulsive interactions in affecting vehicle performance is also investigated.
    Keywords: Spacecraft Design, Testing and Performance
    Type: NASA-CR-202601 , NAS 1.26:202601 , AIAA Paper 94-3524
    Format: text
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  • 5
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    Flight Dynamics and Control of Elastic Hypersonic Vehicles Uncertainty Modeling (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It has been shown previously that hypersonic air-breathing aircraft exhibit strong aeroelastic/aeropropulsive dynamic interactions. To investigate these, especially from the perspective of the vehicle dynamics and control, analytical expressions for key stability derivatives were derived, and an analysis of the dynamics was performed. In this paper, the important issue of model uncertainty, and the appropriate forms for representing this uncertainty, is addressed. It is shown that the methods suggested in the literature for analyzing the robustness of multivariable feedback systems, which as a prerequisite to their application assume particular forms of model uncertainty, can be difficult to apply on real atmospheric flight vehicles. Also, the extent to which available methods are conservative is demonstrated for this class of vehicle dynamics.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA-CR-202600 , NAS 1.26:202600 , AIAA Paper 94-3629
    Format: text
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  • 6
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    Analysis of airframe/engine interactions - An integrated control perspective (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Techniques for the analysis of the dynamic interactions between airframe/engine dynamical systems are presented. Critical coupling terms are developed that determine the significance of these interactions with regard to the closed loop stability and performance of the feedback systems. A conceptual model is first used to indicate the potential sources of the coupling, how the coupling manifests itself, and how the magnitudes of these critical coupling terms are used to quantify the effects of the airframe/engine interactions. A case study is also presented involving an unstable airframe with thrust vectoring for attitude control. It is shown for this system with classical, decentralized control laws that there is little airframe/engine interaction, and the stability and performance with those control laws is not affected. Implications of parameter uncertainty in the coupling dynamics is also discussed, and effects of these parameter variations are also demonstrated to be small for this vehicle configuration.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 90-1918
    Format: text
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  • 7
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    A comparative study of multivariable robustness analysis methods as applied to integrated flight and propulsion control (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Three multivariable robustness analysis methods are compared and contrasted. The focus of the analysis is on system stability and performance robustness to uncertainty in the coupling dynamics between two interacting subsystems. Of particular interest is interacting airframe and engine subsystems, and an example airframe/engine vehicle configuration is utilized in the demonstration of these approaches. The singular value (SV) and structured singular value (SSV) analysis methods are compared to a method especially well suited for analysis of robustness to uncertainties in subsystem interactions. This approach is referred to here as the interacting subsystem (IS) analysis method. This method has been used previously to analyze airframe/engine systems, emphasizing the study of stability robustness. However, performance robustness is also investigated here, and a new measure of allowable uncertainty for acceptable performance robustness is introduced. The IS methodology does not require plant uncertainty models to measure the robustness of the system, and is shown to yield valuable information regarding the effects of subsystem interactions. In contrast, the SV and SSV methods allow for the evaluation of the robustness of the system to particular models of uncertainty, and do not directly indicate how the airframe (engine) subsystem interacts with the engine (airframe) subsystem.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 93-3809 , In: AIAA Guidance, Navigation and Control Conference, Monterey, CA, Aug. 9-11, 1993, Technical Papers. Pt. 2 (A93-51301 22-63); p. 984-994.
    Format: text
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  • 8
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    Dynamics of hypersonic flight vehicles exhibiting significant aeroelastic and aeropropulsive interactions (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: With analytic expressions previously developed for the forces and moments acting on a generic hypersonic vehicle, it is of interest to investigate the relative importance of the aerodynamic and propulsive effects on the vehicle dynamics. It is shown that the vehicle's aerodynamics and propulsive forces are both very significant in the evaluation of key stability derivatives which dictate the vehicle's dynamic characteristics. It is also shown that the vehicle model selected is unstable in pitch and exhibits strong airframe/engine/elastic coupling. With the use of literal expressions for both the systems poles and zeros, as well as the stability derivatives, key vehicle dynamic characteristics are investigated. For small errors, or uncertainties, in either the aerodynamic or propulsive forces, significant errors in the frequency and damping of the dominant modes and zero locations will arise.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 93-3763 , In: AIAA Guidance, Navigation and Control Conference, Monterey, CA, Aug. 9-11, 1993, Technical Papers. Pt. 1 (A93-51301 22-63); p. 561-568.
    Format: text
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  • 9
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    Integrated control of hypersonic vehicles - A necessity not just a possibility (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The unique problems to be encountered in the design of systems for the precise control of hypersonic vehicles are to be reviewed and discussed. These problems pose significant research challenges if successful guidance and control systems are to be developed for this new class of vehicle. These challenges will be shown to arise due to the stringent mission requirements on the vehicle, and the highly integrated configuration designs being considered. In this paper, the mission requirements and operational goals of these vehicles will be first reviewed, and the trajectory performance issues highlighted. Then the presence of critical coupling between several vehicular subsystems will be clearly exposed, and the dynamic interactions between these subsystems will be presented. The results to be discussed are based on the analysis of a generic hypersonic vehicle, with characteristics similar to the X-30. It is an unstable, highly-coupled, aeropropulsive/aeroelastic system, with large variations in its attitude-dynamic characteristics over its extensive flight envelope. The genesis of these interactions is explored, the magnitudes quantified, and their significance in the context of control-system design presented. Finally, some candidate designs for the highly-integrated control systems will be presented.
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: AIAA PAPER 93-3761 , In: AIAA Guidance, Navigation and Control Conference, Monterey, CA, Aug. 9-11, 1993, Technical Papers. Pt. 1 (A93-51301 22-63); p. 539-549.
    Format: text
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  • 10
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    Modeling and model simplification of aeroelastic vehicles: An overview (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The rigid-body degrees of freedom and elastic degrees of freedom of aeroelastic vehicles are typically treated separately in dynamic analysis. Such a decoupling, however, is not always justified and modeling assumptions that imply decoupling must be used with caution. The frequency separation between the rigid-body and elastic degrees of freedom for advanced aircraft may no longer be sufficient to permit the typical treatment of the vehicle dynamics. Integrated, elastic vehicle models must be developed initially and simplified in a manner appropriate to and consistent with the intended application. This paper summarizes key results from past research aimed at developing and implementing integrated aeroelastic vehicle models for flight controls analysis and design. Three major areas will be addressed: (1) the accurate representation of the dynamics of aeroelastic vehicles, (2) properties of several model simplification methods, and (3) the importance of understanding the physics of the system being modeled and of having a model which exposes the underlying physical causes for critical dynamic characteristics.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TM-107691 , NAS 1.15:107691
    Format: application/pdf
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