Towards Biomimetic Morphing of Aircraft Wings: Feedback Control of Aerofoil Section Shape

摘要

A morphing aircraft wing is one with deformable aerofoil sections that have the ability and the control actuation necessary to change their shape in flight. It has been demonstrated in many studies that morphing of aerofoil shape leads to substantial aerodynamic performance benefits in general and can be used for purposes of drag reduction. In fact it is possible to directly relate the improvements in drag that can be achieved and the magnitude of the shape changes needed. While morphing has been proposed as an alternative to conventional control surfaces, the ability to morph wings with conventional control surfaces can greatly improve their performance. In this paper, the effectiveness of morphing an aerofoil section through deformation in order to reduce the drag at the off design angle of attack is investigated. The configuration of the aerofoil is deformed, under practical structural restrictions, relative to the configuration of the wing box. A typical aerofoil section is chosen as the baseline aerofoil. Aerodynamic characteristics of the baseline and deformed aerofoils have been investigated using a variety of aerofoil analysis methods such as the panel method in incompressible flow, the transonic full potential solution in the transonic regime and Drela's method (XFOIL code) to include viscous effects. These methods were chosen as they must be solved sufficiently fast (in real time). The transonic case was also considered as most commercial airliners fly near Mach one. It is shown that the section deformation can be effective in reducing the drag at the off-design angle-of-attack, in comparison with the baseline aerofoil. A typical pressure distribution of the desired aerofoil with the desired lift, moment and drag characteristics is chosen and an inverse aerofoil design approach is adopted to find the aerofoil shape. The aerofoil is assumed to designed and constructed by wrapping an appropriate membrane around a core wing box fitted with actuators capable of deforming the outer aerofoil section. Several cases of fully actuated and under-actuated servos are considered with different models of uncertainty. A complete distributed modelling and feedback control scheme is proposed and validated so as to morph the baseline aerofoil design to the desired aerofoil design. Thus the scheme illustrates a feasible technique for achieving drag reduction via aerofoil shape control in real time and to deliver a desired pressure distribution in real time.