Interactions of Aircraft Design and Control: Actuators Sizing and Optimization for an Unstable Blended Wing-Body

Abstract

In this paper the problem of integrated design and control for a civil blended wing-body aircraft is addressed. Indeed this configuration faces remarkable challenges related to handling qualities: namely the aircraft configuration in this study features a strong longitudinal instability for some specific flight points. Moreover it may lack control efficiency despite large and redundant movables. Stabilizing such a configuration may then lead to high control surfaces rates, meaning significant energy penalty and installation mass for flight control actuators, as well as challenges for actuators space allocation. Those penalties should therefore be taken into account early in the conceptual design phase, instead of being checked afterwards. Our approach consists in simultaneously designing a stabilizing controller and actuators dynamic characteristics, namely their bandwidth, for a given aircraft configuration. Our method relies on latest developments on nonsmooth optimization techniques for robust control design. For any aircraft configuration, guaranteed stability performance, as well as optimized control surfaces allocation with respect to their relative efficiency and inertia, are obtained. From these results, a segregation among trim and maneuver control surfaces is obtained, with guarantee that the later ones are able to cope with aircraft instability. Then it is checked that remaining trim control surfaces are sufficient for equilibrating the aircraft in any flight condition. This approach allows for a fast prototyping of control surfaces and actuators for unstable configurations. Different control surfaces layouts are evaluated in order to show the exibility of the method.