Close-Formation Flight Control with Motion Synchronization

Introduction F ORMATION flight of multiple aircraft has been an active research topic for many years. For the classical lead–follower configuration, when the follower is properly positioned with respect to the lead, the drag on the follower aircraft can be remarkably reduced due to strong wingtip vortices generated by the lead aircraft. Such close-formation flight configurations can lead to reduction in fuel consumption and, thus, an increase in flight range. Previous formation flight of a pair of Dryden F/A-18s shows a 20% drag reduction and 18% fuel saving.1 The high efficiency of close-formation flight relies on accurate relative position control between the follower and the lead aircraft, especially under the effect of coupled aerodynamics. Many control strategies have been proposed to treat close-formation flight with consideration of coupled aerodynamics.2,3 In this Note, a motion synchronization control strategy is proposed to synchronize the relative position tracking motion between multiple follower aircraft. The NASA–Hallock–Burnham vortex profile is adopted to calculate the vortex-induced forces and moments. The autopilot models of the followers are modified with consideration of the coupled aerodynamics. Finally, the simulation results demonstrate the effectiveness and performance improvement with the proposed control method.