Aeroelastic Multi-Surface Roll Control of a Three Surfaces Wind Tunnel Model

Abstract

This paper presents the work done on the aeroelastic demonstrator named XDIA at Politecnico di Milano, dealing with active control, optimization and roll maneuvers. An approach based on usage of multiple control surfaces has been adopted to enhance roll maneuver of a three surface regional transport aircraft. Optimization algorithms based upon genetic algorithms allowed to improve roll maneuver in two different ways: reducing overall surface deflection and improving aircraft roll rate performances, still reducing wing solicitations during maneuver transients. The additional usage of canard control surfaces, at last has been performed in order to extend solicitation improvement also to fuselage. The following lines will describe the methodology adopted, the models realized and the results so far obtained. ommon jet liners are nowadays showing a huge number of control surfaces, designed and optimized for different purposes, ranging from load enhancement during specific flight moments (lift-off and landing), maneuvering and even gust alleviation. Many of these devices, are deeply optimized for very specific purposes, thus their single contribution to flight improvement is, often, limited to a very specific flight phase. Extending usage of the same control surface to different tasks, might be an option for designing more efficient aircrafts. Recently, at Politecnico di Milano, an unconventional three surface aircraft has been designed, and an aeroelastic wind tunnel has been realized, with the aim of experimenting on the field effects of active aeroelastic control over a redundant number of control surfaces. Literature, already offers some interesting results about the matter, for example, Raveh and Zink 1, 2 already solved a similar problem addressing improvements of light maneuvers using a redundant number of control surfaces on the wing; moreover, also KTH 3 proved the applicability of such a concept to a common sweep wing. Here the same concept is applied to a three surface regional transport aircraft, provided of eight control surfaces, located on wing leading and trailing edge. These control surfaces, do provide a sort of adaptivity to the wing itself, serving formally as tabs, ailerons, spoilers and high lift devices and aeroelastic response devices, respectively all at the same time. Formally the wing might appear together as a mix of a Mission Adaptive Wing 4, 5 and an Active Adaptive Wing, 6 and has already been used to test and validate some damping systems based on classic concepts such as Identical Location of Acceleration and Forces (ILAF) 7 and Aerodynamic Energy Concepts. 8–10 The aim of the present paper is to show the progress of the research on this aircraft and the possible improvement which could be offered by usage of a high number of control surfaces to perform common flight maneuvers: in this specific case, roll maneuver has been here chosen as a test case. When addressing roll maneuver, aileron are usually involved. Deflection of these control surfaces, causes load distribution variation, and, obviously, as when aeroelasticity is taken into account, also structural deformations. Just because of aeroelasticity, then, whenever a forward swept wing is adopted, structural deformation may become a delicate issue, as a uncontrolled lift distribution variation, can lead to a load increase due to elastic effects. In this view, the choice of using a redundant number of control surfaces (typically two leading and trailing edge control surfaces and in some cases also usage of canards or horizontal planes), might result favorable to improve either aircraft flight handling qualities and exploit structural deformations caused by aerodynamic load variations in a more efficient manner. This leads to the formulation of an optimization problem that solves roll maneuver trying to minimize structural deformations, still improving aircraft handling qualities (roll rate and roll angle).