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  • 1
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    Synthesis of a helicopter full-authority controller (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 15; 222-227
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Application and flight test of linearizing transformations using measurement feedback to the nonlinear control problem (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The design of nonlinear controllers has relied on the use of detailed aerodynamic and engine models that must be associated with the control law in the flight system implementation. Many of these controllers were applied to vehicle flight path control problems and have attempted to combine both inner- and outer-loop control functions in a single controller. An approach to the nonlinear trajectory control problem is presented. This approach uses linearizing transformations with measurement feedback to eliminate the need for detailed aircraft models in outer-loop control applications. By applying this approach and separating the inner-loop and outer-loop functions two things were achieved: (1) the need for incorporating detailed aerodynamic models in the controller is obviated; and (2) the controller is more easily incorporated into existing aircraft flight control systems. An implementation of the controller is discussed, and this controller is tested on a six degree-of-freedom F-15 simulation and in flight on an F-15 aircraft. Simulation data are presented which validates this approach over a large portion of the F-15 flight envelope. Proof of this concept is provided by flight-test data that closely matches simulation results. Flight-test data are also presented.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TP-3154 , H-1629 , NAS 1.60:3154
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    A two-time-scale autopilot for high-performance aircraft (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A two-time-scale autopilot is proposed for the Aircraft Controls Design Challenge problem. This control law uses a nonlinear aircraft model constructed from the given vehicle simulation. The vehicle model is partitioned into slow translational dynamics and fast rotational dynamics. Feedback linearization is then employed to synthesize control laws for these two-time scales. Due to the nature of the synthesis, the control law is suitable for automatic trajectory following, and also for pilot control.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 91-2674
    Format: text
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  • 4
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    Nonlinear feedback guidance law for aero-assisted orbit transfer maneuvers (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Aero-assisted orbit transfer vehicles have the potential for significantly reducing the fuel requirements in certain classes of orbit transfer operations. Development of a nonlinear feedback guidance law for performing aero-assisted maneuvers that accomplish simultaneous change of all the orbital elements with least vehicle acceleration magnitude is discussed. The analysis is based on a sixth order nonlinear point-mass vehicle model with lift, bank angle, thrust and drag modulation as the control variables. The guidance law uses detailed vehicle aerodynamic and the atmosphere models in the feedback loop. Higher-order gravitational harmonics, planetary atmosphere rotation and ambient winds are included in the formulation. Due to modest computational requirements, the guidance law is implementable on-board an orbit transfer vehicle. The guidance performance is illustrated for three sets of boundary conditions.
    Keywords: ASTRODYNAMICS
    Type: NASA-CR-190129 , NAS 1.26:190129
    Format: application/pdf
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  • 5
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    A study of aircraft cruise (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The long range aircraft cruise problem is analyzed using a model intermediate in complexity between energy model and point mass model. It is shown that this formulation imbeds the classical steady state cruise as the central member along with several other oscillatory extremals. The oscillatory cruise trajectories are shown to exist if the Hessian of the function QD/VT with respect to altitude and airspeed is positive definite. An expression for predicting the frequency of oscillation is developed. Qualitative effects of increasing the vehicle thrust and improving the L/D are discussed. Numerical results for two fighter aircraft and a transport aircraft are given. While oscillatory cruise mode exists for the two fighter aircraft, steady state cruise at full throttle is found to be optimal for the transport aircraft. A second variation analysis to bring out the reason for fuel savings is developed. It is shown that whenever the Hessian of the function QD/VT is positive definite, the second variation will be zero along the classical steady state cruise arc, indicating that a neighboring extremal is competitive. Comparisons with the previous point mass and energy modeled results are given.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 86-2286
    Format: text
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  • 6
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    Flight test trajectory controller synthesis with constrained eigenstructure assignment (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The design of a maneuver autopilot for flight test trajectory control using constrained eigenvalue/eigenvector assignment is examined. The aircraft considered was a high-performance fighter with a command augmentation system engaged in all three axes. Attention is given to difficulties encountered in the generation of the desired eigenvalues and eigenvectors. It is found that this approach demands several iterations to converge to a satisfactory result, and does not appear to easily yield suitable insight for the output feedback design of high-order multivariable systems which will be used at other operating points. It is concluded that this technique could be made more attractive by generating gradients of the eigensystem between flight conditions, and including this information in the single-point design technique.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Format: text
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  • 7
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    Singular optimal control and the identically non-regular problem in the calculus of variations (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A small but interesting class of optimal control problems featuring a scalar control appearing linearly is equivalent to the class of identically nonregular problems in the Calculus of Variations. It is shown that a condition due to Mancill (1950) is equivalent to the generalized Legendre-Clebsch condition for this narrow class of problems.
    Keywords: CYBERNETICS
    Format: text
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  • 8
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    Flight test maneuver modeling and control (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The use of automated flight test schemes decrease the aircraft flight testing time and pilot work load while enhancing the data quality. Two major elements involved in developing such an automated technique are maneuver modeling to generate command histories from the maneuver specifications and the synthesis of control systems to track these command histories. This paper describes the maneuver modeling for eight flight test trajectories. The control system synthesis with Kosut's suboptimal minimum error excitation linear quadratic regulator approach is presented. The closed-loop simulation results are given.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 86-0426
    Format: text
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  • 9
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    Optimal helicopter trajectory planning for terrain following flight (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Helicopters operating in high threat areas have to fly close to the earth surface to minimize the risk of being detected by the adversaries. Techniques are presented for low altitude helicopter trajectory planning. These methods are based on optimal control theory and appear to be implementable onboard in realtime. Second order necessary conditions are obtained to provide a criterion for finding the optimal trajectory when more than one extremal passes through a given point. A second trajectory planning method incorporating a quadratic performance index is also discussed. Trajectory planning problem is formulated as a differential game. The objective is to synthesize optimal trajectories in the presence of an actively maneuvering adversary. Numerical methods for obtaining solutions to these problems are outlined. As an alternative to numerical method, feedback linearizing transformations are combined with the linear quadratic game results to synthesize explicit nonlinear feedback strategies for helicopter pursuit-evasion. Some of the trajectories generated from this research are evaluated on a six-degree-of-freedom helicopter simulation incorporating an advanced autopilot. The optimal trajectory planning methods presented are also useful for autonomous land vehicle guidance.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: NASA-CR-177607 , NAS 1.26:177607
    Format: application/pdf
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  • 10
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    A fast algorithm for image-based ranging (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Image-based ranging has emerged as a critical issue in the low altitude operation of flight vehicles such as rotorcraft and planetary landers. These flight regimes require ranging systems for recovering the geometry of the terrain and obstacles for use with guidance algorithms. The development of a ranging equation combining image irradiance together with various order spatial partial derivatives and the vehicle motion parameters is discussed. The ranging equation is in the form of a polynomial in scene depth. Two-dimensional linear filters are then used to compute the coefficients of this polynomial to result in a fast image-based ranging algorithm. Performance of the algorithm is demonstrated using laboratory images.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Sensors and sensor systems for guidance and navigation; Proceedings of the Meeting, Orlando, FL, Apr. 2, 3, 1991 (A93-27043 09-19); p. 190-200.
    Format: text
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