Aeroelastic behavior of an adaptive lifting surface
Abstract
The use of an adaptive structure to control the static aeroelastic behavior of a lifting surface is examined. The wing structure is modeled as a laminated beam with bending and torsional deformation freedom. Actuation is provided by piezoelectric materials embedded in the wing structural laminate. The structure is made adaptive by employing a feedback control system that applies a voltage to the piezoelectric material layers in direct proportion to the wing root loads. Lift effectiveness, static stability, and rolling behavior of the wing are controlled by varying the feedback gain. Both differential equation and discrete model approaches are used in the analysis. In the differential equation model the structure is represented by beam theory and the aerodynamics by strip theory. The discrete model includes finite wing aerodynamics and an influence coefficient based structural theory. Beam elastic properties and electromechanical coefficients are obtained from a one dimensional laminated beam theory based on classical laminated plate theory. It is shown that the lift effectiveness of a wing can be increased or decreased with respect to its nonadaptive behavior by controlling the feedback gain. The adaptive structure may also be used to increase the divergence dynamic pressure of the wing. However, the ability to modify lift effectiveness is found to be limited by properties of the piezoelectric material, including its stiffness, electromechanical coupling coefficient, maximum electric field and the manner in which it is integrated into the wing structure. A nondimensional parameter that relates aerodynamic measures of performance to piezoelectric material properties is derived. An example is presented to illustrate the capabilities of currently available piezoelectric materials. The adaptive structure approach is also used to alter the rolling power, damping in roll and steady state roll effectiveness of a uniform wing by varying the feedback gain. It is shown that the adaptive structure may be used to increase or decrease the rolling power of a wing with a control surface. Damping in roll can also be actively controlled. Simultaneously controlling rolling power and roll damping can be used to modify the steady state roll rate.
Degree
Ph.D.
Advisors
Weisshaar, Purdue University.
Subject Area
Aerospace materials
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.