Minimum-Drag Fault-Tolerant Aircraft Control Allocation via Online Lifting Line Calculation

Abstract

The minimization of drag at any given flight condition is necessary for the reduction of aircraft fuel consumption and is strongly linked to the way the different aerodynamic surfaces are deflected to control the flight trajectory. Current optimal control allocation methods calculate commands that minimize norm-based metrics that are only loosely related to aircraft drag. In this paper, using a novel real-time application of the lifting line concept, a new control allocation method for overactuated “biomorphic” fixed-wing aircraft is introduced, aiming at addressing the above limitation. The proposed technique outputs optimal, fault-tolerant minimum-drag control allocation solutions for vehicles with large numbers of aerodynamic surfaces, combined with angle-of-attack and angle-of-sideslip estimator functions that allow for direct, localized control of the lift force vectors. Owing to its close link to lifting line theory, which constitutes an integral part of the proposed allocation calculation, the method represents a low-computational-cost solution to the control allocation problem, easily adaptable to different aircraft configurations. Alongside its theoretical development and stability analysis, a series of simulated experiments are presented that demonstrate the proposed method’s characteristics and potential applications.