Modeling, Simulation and Control of Close Formation Flight

In this paper, we focus on the aerodynamic characteristics of aircraft flying in tight formation. The formation model of a small unmanned aircraft is studied, and the disturbance of the wake induced velocity produced by the forward aircrafts on the tail aircraft is analyzed. It is found that the lead aircraft has a significant effect on uplift and drag on the trailing airplane. This has also demonstrated that the tail planes’ aerodynamic characteristics can be enhanced when the following plane is in the proper position of the leader in the tight formation flight. Precise position control of the tail plane in general flight operations is achieved under the influence of the tail vortex. First, the mathematical model of the leader's wake vortex was developed, and then two unmanned aerial vehicles (UAVs) were simulated using computational fluid dynamics (CFD) software to verify accuracy of this mathematical model. A control algorithm was designed to realize the stability of formation flight. Mathematical simulation and validation were performed. The designed control law is able to keep the tail plane in the appropriate position in the formation flight so that the tail plane is subjected to the maximum lift.