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Modification of a helicopter inverse simulation to include an enhanced rotor model

JOURNAL OF AIRCRAFT 2000年第3期37卷 536-538页

作者： Doyle, SA Thomson, DG Univ Glasgow Dept Aerosp Engn Glasgow G12 8QQ Lanark Scotland

An individual blade rotor model has been developed at the University of Glasgow by Rutherford and Thomson (1997) for use in helicopter inverse simulation. In the context of helicopter flight dynamics, an inverse simulation generates the control time histories for the modeled helicopter performing a defined task. To implement such a model in an inverse sense, it is necessary to adopt a numerical integration technique similar to that proposed by Hess et al. (1991). The generic inverse simulation algorithm (Genisa) used by Rutherford and Thomson is essentially a modification of that documented by Hess et al. and is driven by specified maneuver constraints. The helicopter individual blade rotor model (Hibrom) represents the state of the art in helicopter inverse simulation. Among some of the simplifying assumptions made in its development was the assumption of constant rotor speed. This degree of freedom has a direct influence on the dynamic behavior of the main rotor, and its inclusion must be achieved before other modeling features, such as lead/lag freedom, can be incorporated. This paper describes modifications made to the inverse algorithm Genisa that allow the rotor-speed degree of freedom to be incorporated within Hibrom. An engine governor model was successfully incorporated into Hibrom for helicopter inverse simulation. Hence, the rotor speed is now a degree of freedom within the modeled system. The addition of the rotor-speed degree of freedom does not significantly affect the predicted control time histories for the maneuver considered in this study. However, as the boundaries of the flight envelope are approached, it may be expected that the enhanced rotor model will be closer to predicting actual flight behavior. (AIAA)

关键词： Helicopters Numerical Integration Aerodynamic Force Aerospace Engineering Nonlinear Systems Six Degree of Freedom Trailing Edge Flap solution algorithm Dynamic Response Frequency Domain

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INTERACTIVE GRAPHICS FOR GEOMETRY GENERATION - A PROGRAM WITH A CONTEMPORARY DESIGN

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JOURNAL OF AIRCRAFT 1985年第12期22卷 1054-1058页

作者： LABOZZETTA, WF COLE, PE Lockheed-Georgia Company Marietta Georgia

The aerodynamic design process is now strongly influenced by the application of advanced computational tools due mainly to recent advances in computer capabilities. Today’s aerodynamic analysis codes require large amounts of geometric data to define the surfaces in sufficient detail for proper analysis. A program has been developed to aid the engineer in generating geometric models for computational aerodynamics codes. The program, Interactive Graphics for Geometry Generation (I3G), is not dramatically different on the “outside” from other interactive graphics programs of this type. It is, however, different on the “inside,” i.e., in how it performs its functions. I3G is capable of accepting input from a variety of geometry sources and can support the generation of geometric models for many different computational codes. User-friendly operation encourages program use. Graphics devices ranging from sophisticated systems to low-cost display-only terminals can be easily supported by I3G. The program’s modular structure allows new modeling capabilities to be readily incorporated. A system for indexing and retrieving existing geometric models is available to the user. In summary, “flexibility” is the key word behind I3G’s basic design and structure. This feature allows modifications and enhancements to be readily made as needs change or arise. Succinctly, it is a program designed to last. © 1985 American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Computational Aerodynamics Data Store CAD System Data Storage Aerodynamic Codes Interactive Computer Graphics Structured Programming solution algorithm Computing Hardware

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PASSIVE VENTING SYSTEM FOR MODIFYING CAVITY FLOWFIELDS AT SUPERSONIC SPEEDS

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AIAA JOURNAL 1988年第3期26卷 374-376页

作者： WILCOX, FJ NASA Langley Research Center Hampton Virginia

The drag of airfoils in transonic flow may be reduced through the use of a passive venting system that uses a porous plate for part of the airfoil upper surface with a vent chamber beneath the porous plate. This arrangement allows air from a high-pressure region on the airfoil surface to be vented to a low-pressure region, thereby modifying the airfoil flow field and resulting indrag reduction. Using this approach, an existing cavity model was modified to house a porous floor with a vent chamber beneath the floor. The expectation was that for closed cavity flow the high-pressure air at the rear of the cavity would vent to the low-pressure region at the front of the cavity, causing the flowfield to switch to open cavity flow. This Note describes the results of an experimental investigation to determine the effectiveness of this passive venting system.

关键词： Drag Coefficient Pressure Coefficient Turbulent Boundary Layer Axisymmetric Flow Transonic Wind Tunnel Supersonic Speed Angle of Attack NASA Langley Research Center solution algorithm Skin Friction Drag

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NONLINEAR RELAXATION QUASI-NEWTON algorithm FOR THE COMPRESSIBLE NAVIER-STOKES EQUATIONS

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AIAA JOURNAL 1993年第1期31卷 57-60页

作者： EDWARDS, JR MCRAE, DS North Carolina State University Raleigh North Carolina 27695

An efficient implicit method for the computation of steady, two-dimensional compressible Navier-Stokes flowfields is presented. The discretization of the governing equations is hybrid in nature, with flux-vector splitting used in the streamwise direction and central differences with flux-limited artificial dissipation used for the transverse fluxes. Line Jacobi relaxation is used to provide a suitable initial guess for a new nonlinear iteration strategy based on line Gauss-Seidel sweeps. The applicability of quasi-Newton methods as convergence accelerators for this and other line relaxation algorithms is examined, and efficient implementations of such techniques are presented. Convergence histories and comparisons with experimental data are presented for a high-speed compression corner interaction. Results indicate a marked improvement in computational efficiency over more conventional upwind relaxation strategies, particularly for flowfields containing large pockets of streamwise subsonic flow.

关键词： Navier Stokes Equations Implicit Methods Subsonic Flow Applied Aerodynamics solution algorithm Primitive Variable Nonlinear Systems Upwind Scheme Jacobi Method Computing

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Unstructured method for flows past bodies in general three-dimensional relative motion

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AIAA JOURNAL 2001年第2期39卷 219-224页

作者： Singh, KP Baysal, O Old Dominion Univ Dept Aerosp Engn Norfolk VA 23529 USA Old Dominion Univ Coll Engn & Technol Norfolk VA 23529 USA

A three-dimensional methodology was developed for unsteady flows past bodies that are in relative motion and where the trajectory of the motion was determined from the instantaneous aerodynamic field. This method coupled the equations of fluid flow and those of rigid-body dynamics and then captured the unsteady aerodynamic interference between the stationary and moving boundaries. The time-dependent, compressible Euler equations were solved on dynamic, unstructured meshes by an explicit, finite volume, and upwind method. The grid adaptation was performed within a window placed around a moving body, The Euler equations of dynamics were then solved by a Runge-Kutta integration scheme. The flow solver and the adaptation scheme were validated by simulating the transonic, unsteady flow around a wing undergoing a forced, periodic pitching motion and then comparing the results with the experimental data. Finally, the overall methodology was demonstrated by simulating the unsteady flowfield and the trajectory of a store dropped from a wing, The methodology, with its computational cost notwithstanding, has proven to be accurate, automated, easy for dynamic gridding, and relatively efficient for the required work hours.

关键词： Aerodynamic Interference Six Degree of Freedom Euler Equations Runge Kutta Integration Rectangular Wing NACA 64A010 Wing Root Domain Decomposition Methods solution algorithm Angle of Attack

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Systematic Procedure for Taxi-Route Conformance Monitoring

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JOURNAL OF AIRCRAFT 2012年第6期49卷 1953-1964页

作者： Zheng, Q. Maggie Zhao, Yiyuan J. Univ Minnesota Dept Aerosp Engn & Mech Minneapolis MN 55455 USA

A systematic procedure for the design and evaluation of a taxi-route conformance-monitoring system is presented. Specifically, two levels of solution algorithms are designed for two different granularities of a complete surface taxi-route conformance-monitoring problem. The macrolevel solutions focus on route identification in which aircraft are assumed to move within the specified taxiways and can only be on one route segment at any given time. The route segment that an aircraft is moving on is then uniquely determined based on a graph model of the airport structure. In comparison, the microlevel solutions identify both lateral position deviation and route deviation to determine if an aircraft stays within the specified taxiways and which routes it is on. It can detect the simultaneous occupancies of an aircraft on multiple route segments at a given time, such as during turns. For the microsolutions, the airport surface is described by a set of geometric shapes. Furthermore, frameworks for applying these algorithms in the presence of uncertainties are developed. Extensive numerical simulations are used to evaluate the performances of the proposed algorithms.

关键词： Taxiway Graph Modeling solution algorithm Numerical Simulation Heading Angle Monte Carlo Simulation Automatic Dependent Surveillance Broadcast Pilot Expendable Launch Vehicle Aircraft Trajectory

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APPLICATION OF POPOV CONTROLLER SYNTHESIS TO BENCHMARK PROBLEMS WITH REAL PARAMETER UNCERTAINTY

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1994年第4期17卷 759-768页

作者： HOW, JP HADDAD, WM HALL, SR MIT SPACE ENGN RES CTRCAMBRIDGEMA 02139 MIT CAMBRIDGEMA 02139

A new approach to robust control design with real parameter uncertainty has been developed using the analysis criteria from absolute stability theory. Both time and frequency domain stability conditions have been investigated, and the results demonstrate that the analysis tests include information about both the phase and structure of the unknown parameters. This paper uses these analysis results to investigate the synthesis of robust controllers. The control design algorithm uses state space optimization techniques to minimize an overbound of the H-2 permormance objective that is developed using the Popov stability criterion. In this technique, the optimal compensator and multiplier coefficients are designed simultaneously, which avoids the D-K iteration of mu synthesis. The procedure is applied to the two and four mass benchmark problems. These examples illustrate that good guaranteed robust performance can be achieved using this Popov controller synthesis (or combined H-2/mixed mu) algorithm.

关键词： Closed Loop Transfer Function Frequency Domain Linear Quadratic Gaussian Broyden Fletcher Goldfarb Shanno Output Feedback Riccati Equations Lagrange Multipliers solution algorithm Mass Spring System Search algorithm

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Smooth Local Correlation-Based Transition Model for the Spalart-Allmaras Turbulence Model

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AIAA JOURNAL 2021年第2期59卷 474-492页

作者： Piotrowski, Michael G. H. Zingg, David W. NASA Ames Res Ctr Moffett Field CA 94035 USA Univ Toronto Computat Aerodynam & Sustainable Aviat Inst Aerosp Studies Toronto ON M3H 5T6 Canada Univ Toronto NASA Computat Aerosci Branch Toronto ON Canada Univ Toronto Inst Aerosp Studies N York ON M3H 5T6 Canada

A smooth version of the gamma-R similar to e theta t local correlation-based transition model (LM2015) for the Spalart-Allmaras (SA) turbulence model is presented. The LM2015 model with helicity-based crossflow correlations is modified and coupled to the SA turbulence model, designated SA-LM2015. The LM2015 and SA-LM2015 transition models include source terms that contain stiff and nonsmooth functions. Approximations to these functions are introduced to eliminate discontinuities and improve the numerical behavior of the model, with the smooth model designated SA-sLM2015. Deep convergence is achieved using a fully coupled, implicit Newton-Krylov algorithm globalized using an efficient pseudotransient continuation strategy. Modifications to the Newton-Krylov algorithm are introduced, including a source-term time stepping strategy, to address the large sources introduced by the turbulence and transition model equations. Two- and three-dimensional transition test cases demonstrate that both models, SA-LM2015 and SA-sLM2015, are able to predict transition due to a variety of mechanisms accurately, with the smooth variant displaying significantly improved numerical behavior. Several of the strategies presented, including the smoothing techniques and source-term time stepping, could be useful in the context of other transition models as well.

关键词： Spalart Allmaras Turbulence Model solution algorithm Angle of Attack Reynolds Averaged Navier Stokes Aerodynamic Shape Optimization Laminar Turbulent Transition Swept Wing Freestream Turbulence Natural Laminar Flow Low Turbulence Pressure Tunnel

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PARABOLIZED NAVIER-STOKES ANALYSIS OF DUCTED SUPERSONIC COMBUSTION PROBLEMS

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JOURNAL OF PROPULSION AND POWER 1987年第5期3卷 455-464页

作者： SINHA, N DASH, SM Science Applications International Corp. Princeton NJ

The extension of a recently developed implicit/explicit approach to analyzing two-dimensional ducted supersonic mixing problems with finite-rate chemistry is presented. The hybrid approach combines a fully implicit parabolic mixing algorithm, an explicit viscous-characteristic-based wave-solver algorithm, and a linearized implicit chemical kinetic solution algorithm. The resultant model provides spatial marching solutions of the parabolized Navier-Stokes (PNS) equations for supersonic combustion problems. Specialized procedures are incorporated to deal with the near-wall sublayer. A parabolic option is available that can be utilized in the direct or inverse mode for design applications. The ability of the model to treat shock waves and wave/mixing layer interactions is assessed via comparisons of predictions with those of well-established, explicit shock-capturing Euler (SCIPPY) and PNS (SCIPVIS) models. Applications to several supersonic combustion flowfield problems are presented that exhibit overall capabilities. © 1987 American Institute of Aeronautics and Astronautics, Inc.

关键词： Supersonic Combustion Mach Angle solution algorithm Combustors Turbulence Models Velocity Profiles Shear Layers Continuity Equation Skin Friction Coefficient Mach Number

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OPTIMIZED ROTATION-AXIS ATTITUDE MANEUVER CONTROLLER FOR THE SPACE-SHUTTLE ORBITER

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1987年第1期10卷 4-13页

作者： REDDING, DC ADAMS, NJ The Charles Stark Draper Laboratory Cambridge Massachusetts

This paper describes a controller for automatic attitude maneuvers of reaction-control-jet-equipped spacecraft. It is based on a new, real-time algorithm for solution of fuel-optimal maneuvers, assuming on-off control and linearized dynamics. These solutions provide efficient model trajectories that are easily tracked using a feed-forward, feedback controller structure. This approach was developed as a software upgrade to the Space Shuttle Orbiter on-orbit autopilot, for which it shows a very substantial performance benefit in a wide range of simulated maneuver tasks.

关键词： Space Shuttle Orbiter Autopilot Reaction Control System Earth Open Loop solution algorithm Roll Control Spacecraft Dynamics Spacecraft Control Numerical algorithms

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