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  • 1
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    Flight Investigation of Prescribed Simultaneous Independent Surface Excitations for Real-Time Parameter Identification (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Near real-time stability and control derivative extraction is required to support flight demonstration of Intelligent Flight Control System (IFCS) concepts being developed by NASA, academia, and industry. Traditionally, flight maneuvers would be designed and flown to obtain stability and control derivative estimates using a postflight analysis technique. The goal of the IFCS concept is to be able to modify the control laws in real time for an aircraft that has been damaged in flight. In some IFCS implementations, real-time parameter identification (PID) of the stability and control derivatives of the damaged aircraft is necessary for successfully reconfiguring the control system. This report investigates the usefulness of Prescribed Simultaneous Independent Surface Excitations (PreSISE) to provide data for rapidly obtaining estimates of the stability and control derivatives. Flight test data were analyzed using both equation-error and output-error PID techniques. The equation-error PID technique is known as Fourier Transform Regression (FTR) and is a frequency-domain real-time implementation. Selected results were compared with a time-domain output-error technique. The real-time equation-error technique combined with the PreSISE maneuvers provided excellent derivative estimation in the longitudinal axis. However, the PreSISE maneuvers as presently defined were not adequate for accurate estimation of the lateral-directional derivatives.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212029 , H-2544 , NAS 1.15:212029 , AIAA Atmospheric Flight Mechanics Conference and Exhibit; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Real-Time Stability and Control Derivative Extraction From F-15 Flight Data (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A real-time, frequency-domain, equation-error parameter identification (PID) technique was used to estimate stability and control derivatives from flight data. This technique is being studied to support adaptive control system concepts currently being developed by NASA (National Aeronautics and Space Administration), academia, and industry. This report describes the basic real-time algorithm used for this study and implementation issues for onboard usage as part of an indirect-adaptive control system. A confidence measures system for automated evaluation of PID results is discussed. Results calculated using flight data from a modified F-15 aircraft are presented. Test maneuvers included pilot input doublets and automated inputs at several flight conditions. Estimated derivatives are compared to aerodynamic model predictions. Data indicate that the real-time PID used for this study performs well enough to be used for onboard parameter estimation. For suitable test inputs, the parameter estimates converged rapidly to sufficient levels of accuracy. The devised confidence measures used were moderately successful.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212027 , H-2542 , NAS 1.15:212027 , AIAA Atmospheric Flight Mechanics Conference; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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    NASA TECHNICAL REPORTS
  • 3
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    Measurement uncertainty and feasibility study of a flush airdata system for a hypersonic flight experiment (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Presented is a feasibility and error analysis for a hypersonic flush airdata system on a hypersonic flight experiment (HYFLITE). HYFLITE heating loads make intrusive airdata measurement impractical. Although this analysis is specifically for the HYFLITE vehicle and trajectory, the problems analyzed are generally applicable to hypersonic vehicles. A layout of the flush-port matrix is shown. Surface pressures are related airdata parameters using a simple aerodynamic model. The model is linearized using small perturbations and inverted using nonlinear least-squares. Effects of various error sources on the overall uncertainty are evaluated using an error simulation. Error sources modeled include boundarylayer/viscous interactions, pneumatic lag, thermal transpiration in the sensor pressure tubing, misalignment in the matrix layout, thermal warping of the vehicle nose, sampling resolution, and transducer error. Using simulated pressure data for input to the estimation algorithm, effects caused by various error sources are analyzed by comparing estimator outputs with the original trajectory. To obtain ensemble averages the simulation is run repeatedly and output statistics are compiled. Output errors resulting from the various error sources are presented as a function of Mach number. Final uncertainties with all modeled error sources included are presented as a function of Mach number.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4627 , H-2010 , NAS 1.15:4627 , AIAA PAPER 94-1930 , Applied Aerodynamics Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
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  • 4
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    Flight Stability and Control and Performance Results from the Linear Aerospike SR-71 Experiment (LASRE) (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Linear Aerospike SR-71 Experiment (LASRE) is presently being conducted to test a 20-percent-scale version of the Linear Aerospike rocket engine. This rocket engine has been chosen to power the X-33 Single Stage to Orbit Technology Demonstrator Vehicle. The rocket engine was integrated into a lifting body configuration and mounted to the upper surface of an SR-71 aircraft. This paper presents stability and control results and performance results from the envelope expansion flight tests of the LASRE configuration up to Mach 1.8 and compares the results with wind tunnel predictions. Longitudinal stability and elevator control effectiveness were well-predicted from wind tunnel tests. Zero-lift pitching moment was mispredicted transonically. Directional stability, dihedral stability, and rudder effectiveness were overpredicted. The SR-71 handling qualities were never significantly impacted as a result of the missed predictions. Performance results confirmed the large amount of wind-tunnel-predicted transonic drag for the LASRE configuration. This drag increase made the performance of the vehicle so poor that acceleration through transonic Mach numbers could not be achieved on a hot day without depleting the available fuel.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-1998-206565 , H-2276 , NAS 1.15:206565 , Atmosphere Flight Mechanics; Aug 10, 1998 - Aug 12, 1998; Boston, MA; United States
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  • 5
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    Results From F-18B Stability and Control Parameter Estimation Flight Tests at High Dynamic Pressures (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A maximum-likelihood output-error parameter estimation technique has been used to obtain stability and control derivatives for the NASA F-18B Systems Research Aircraft. This work has been performed to support flight testing of the active aeroelastic wing (AAW) F-18A project. The goal of this research is to obtain baseline F-18 stability and control derivatives that will form the foundation of the aerodynamic model for the AAW aircraft configuration. Flight data have been obtained at Mach numbers between 0.85 and 1.30 and at dynamic pressures ranging between 600 and 1500 lbf/sq ft. At each test condition, longitudinal and lateral-directional doublets have been performed using an automated onboard excitation system. The doublet maneuver consists of a series of single-surface inputs so that individual control-surface motions cannot be correlated with other control-surface motions. Flight test results have shown that several stability and control derivatives are significantly different than prescribed by the F-18B aerodynamic model. This report defines the parameter estimation technique used, presents stability and control derivative results, compares the results with predictions based on the current F-18B aerodynamic model, and shows improvements to the nonlinear simulation using updated derivatives from this research.
    Keywords: Aircraft Stability and Control
    Type: NASA/TP-2000-209033 , H-2424 , NAS 1.60:209033
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Stability and Control Estimation Flight Test Results for the SR-71 Aircraft With Externally Mounted Experiments (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A maximum-likelihood output-error parameter estimation technique is used to obtain stability and control derivatives for the NASA Dryden Flight Research Center SR-71A airplane and for configurations that include experiments externally mounted to the top of the fuselage. This research is being done as part of the envelope clearance for the new experiment configurations. Flight data are obtained at speeds ranging from Mach 0.4 to Mach 3.0, with an extensive amount of test points at approximately Mach 1.0. Pilot-input pitch and yaw-roll doublets are used to obtain the data. This report defines the parameter estimation technique used, presents stability and control derivative results, and compares the derivatives for the three configurations tested. The experimental configurations studied generally show acceptable stability, control, trim, and handling qualities throughout the Mach regimes tested. The reduction of directional stability for the experimental configurations is the most significant aerodynamic effect measured and identified as a design constraint for future experimental configurations. This report also shows the significant effects of aircraft flexibility on the stability and control derivatives.
    Keywords: Aircraft Stability and Control
    Type: NASA/TP-2002-210718 , H-2465 , NAS 1.60:210718
    Format: application/pdf
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