Actuator and Aerodynamic Modeling for High-Angle-of-Attack Aeroservoelasticity

Brenner, Martin J. (1993) Actuator and Aerodynamic Modeling for High-Angle-of-Attack Aeroservoelasticity. Technical Report NASA TM-4493, Research Engineering, NASA Dryden Flight Research Center.

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Abstract

Accurate prediction of airframe/actuation coupling is required by the imposing demands of modern flight control systems. In particular, for agility enhancement at high angle of attack and low dynamic pressure, structural integration characteristics such as hinge moments, effective actuator stiffness, and airframe/control surface damping can have a significant effect on stability predictions. Actuator responses are customarily represented with low-order transfer functions matched to actuator test data, and control surface stiffness is often modeled as a linear spring. The inclusion of the physical properties of actuation and its installation on the airframe is therefore addressed in this paper using detailed actuator models which consider the physical, electrical, and mechanical elements of actuation. The aeroservoelastic analysis procedure is described in which the actuators are modeled as detailed high-order transfer functions and as approximate low-order transfer functions. The impacts of unsteady aerodynamic modeling on aeroservoelastic stability are also investigated in this paper by varying the order of approximation, or number of aerodynamic lag states, in the analysis. Test data from a thrust-vectoring configuration of an F/A-18 aircraft are compared to predictions to determine the effects on accuracy as a function of modeling complexity.

EPrint Type:	NASA Technical Memorandum
Keywords:	Actuator dynamics, Aeroservoelasticity, High angle of attack, Modal stability, Structural dynamics, Unsteady aerodynamics
Subjects:	Aircraft/Project: F-18 HARV (01 - 09) Aeronautics: (05) Aircraft Design, Testing And Performance (01 - 09) Aeronautics: (08) Aircraft Stability And Control
ID Code:	1056
Deposited On:	24 August 2006
Additional Information:	30 pages. Also presented as AIAA-93-1419 at the AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, AIAA/ASME Adaptive Structures Forum, La Jolla, California, April 19–22. 1993.