Vertically optimal close formation flight control based on wingtip vortex structure

In this paper, aiming to drive the unmanned aerial vehicle (UAV) to the optimal position of the vertical plane in the close formation flight, a control method that is based on extended state observer (ESO) and wingtip vortex structure is proposed. This method is suitable for cases where the optimal position is unknown and there are gusts. The scheme is divided into three parts. In the first part, an ESO is designed to estimate the change of the lift and other external disturbances on the follower UAV. In the second part, an algorithm making use of the estimates of the change of the lift to predict the optimal position for the follower UAV is proposed. In the third part, to stabilize the UAV around the optimal position, a sliding mode controller is designed and the external disturbances on the follower UAV are compensated by the ESO. The simulation results show that the followers could automatically adjust their spatial positions to track the predicted optimal positions behind the leader UAV and achieve the precisely close formation flight without the information of leader’s altitude.