The futuristic concept of civil autonomous aerial refueling using the Boom-Receptacle system, demands new operational paradigms. Requirements, such as passenger comfort, demand that the Tanker aircraft will approach the Receiver aircraft, unlike the well-practiced manual military procedure today. In this paper, optimal guidance laws are developed and analyzed. The purpose of the guidance law is to steer the Tanker aircraft from its initial offset relative to the Receiver aircraft, until reaching the predefined flight course, path and separation.
Inspired by missile intercept problems, a linear quadratic optimal control problem with terminal intercept angle, and intercept angular rate constraints is posed. The goal is achieved by reducing the relative separation and aligning the velocity vector of both aircraft at the end of the maneuver. Two different guidance laws are presented. The first is based on the separated guidance and control design methodology. The guidance portion is derived based on a first-order lag autopilot model. The second is based on a more detailed model of the Tanker aircraft. The problem is formulated so that the coupling between the relative kinematics and the dynamic model of the Tanker airframe is taken into account, yielding an integrated guidance and control architecture. The ability to achieve mid-air rendezvous is demonstrated using numerical simulations and performance is evaluated.
