Optimization of a flexible composite wing for pull-up maneuver with internal actuation

Abstract

A technique of deforming a flexible wing to hold the airplane in a steady pull-up maneuver with required load factor at high dynamic pressures is examined. A minimum weight design, with constraints on strength for three different flight conditions, on the frequency distribution and lift effectiveness was used for this study. Rather than using an elevator system for pull-up, symmetric elastic twist and camber is determined to achieve the required pitching moment for increase in the angle of attack and change in the pitch rate to generate the required lift forces for pull-up maneuver. The elastic twist and camber is achieved by providing a system of actuating elements distributed within the internal substructure of the wing to provide control forces. The modal approach is used to develop equilibrium equations for the steady pull-up maneuver of a wing subjected to aerodynamic loads and the actuating forces. The distribution of actuating forces required to achieve specified load factor was determined by using an iterative procedure in conjunction with an optimal control design approach. Here, a full-scale flexible realistic wing is considered for the assessment of strain energy as a measure of the necessary power required to produce the symmetric twist and camber deformation to achieve the required lift forces.Three subsonic design conditions are investigated.