Control and Simulation of Relative Motion for Aerial Refueling in Racetrack Maneuvers

Abstract

T HIS paper focuses on the development of an integrated simulation environment and control algorithms for a receiver aircraft in boom–receptacle refueling (BRR) operation while the tanker flies in a racetrack maneuver. A racetrack maneuver is the standard pattern flown by tanker aircraft, with straight legs and bank turns [1]. This paper applies the earlier work by the authors on mathematical modeling of relative motion [2,3] and aerodynamic coupling [4] to the simulation of aerial refueling, and it develops control laws for the motion of the receiver relative to the tanker that flies in racetrack maneuvers. An integrated simulation environment is developed to take into account tanker maneuvers, motion of the receiver relative to the tanker, and the aerodynamic coupling due to the trailingwake vortex of the tanker. The separate dynamicmodel of the tanker, including its own controller, allows the simulation of the standard racetrack maneuvers of the tanker in aerial refueling operations. The mathematical model of the receiver expressed in terms of the relative position and orientation with respect to the tanker’s body frame facilitates the formulation, in a single framework, of maneuver and stationkeeping of the receiver behind the tanker. For the racetrack maneuvers of the tanker, a linear quadratic regulator (LQR)-based multi-input/multi-output (MIMO) state feedback and integral control technique is developed to track commanded speed, altitude, and yaw rate. Similarly, for the relative motion of the receiver, an LQR-based MIMO state feedback and integral control technique is designed to track the commanded trajectory expressed in the body frame of the tanker. Both controllers schedule their corresponding feedback and integral gains based on the commanded speed and yaw rate of the tanker. The tanker aircraft model represents KC-135R, and the receiver aircraft model is a tailless fighter aircraft with innovative control effectors (ICE) and thrust-vectoring capability. Because the receiver has redundant control variables, various control allocation schemes are investigated for trajectory tracking and stationkeeping while the tanker flies in various racetrack maneuvers with different commanded turn rates.