Abstract

Station-keeping control is the basis of autonomous aerial refueling. However, there exist strong external disturbances including the atmospheric turbulence and the wake vortex of the tanker, and the system change caused by the fuel transfer. These present challenges in station-keeping control design. This paper proposes an additive-state-decomposition-based station-keeping control method for autonomous aerial refueling. This method `additively' decomposes the original tracking problem into two more tractable problems, namely a tracking problem for a linear time-invariant primary system and a stabilization problem for a deterministic nonlinear secondary system. Based on the decomposition, a proportional-integral controller is designed for the primary system to track the reference trajectory, and a feedback linearization controller is adopted to solve the stabilization problem for the secondary system. Finally, the two designed controllers are combined to achieve the original control objective. By using additive state decomposition, the proposed control method with two degrees of freedom can satisfy the control requirements of station keeping with constant mass and varying mass. Simulation results demonstrate the effectiveness and robustness of the proposed station-keeping controller.