Induced Drag Reduction Using Aeroelastic Tailoring with Adaptive Control Surfaces

This paper describes the use of full-span deforming control surfaces (including controlled chordwise cambering of the wing) to provide effective subsonic induced drag control with precise control of the spanwise lift distribution. Examples of these proposed controllers are smart, adaptive actuators for advanced unmanned air vehicle concepts. Reshaping the wing spanwise lift distribution with aeroelastic tailoring concepts is shown to reduce induced drag at high airspeeds. Active controllers such as conventional ailerons or leadingedge devices also reduce induced drag if they have a tailored spanwise deflection pattern; the required deflections of these surfaces depend on wing deformation and can be so large that they are not practical. Combining wing aeroelastic stiffness tailoring with active control surface design to create a “control-friendly structure” reduces induced drag and requires only small controller inputs. An exact solution for the actuator deflections to generate an elliptical lift distribution for the aeroelastic wing, for minimum induced drag, is discussed. A formal optimization problem is posed for cases in which multiple surfaces are used to control drag. This controller optimization solution is complicated because aeroelastic phenomena, such as control reversal, limit the effectiveness of some actuators at high speed.