Flight Control and Simulation for Aerial Refueling

This paper addresses the problem of controlling the receiver aircraft to achieve a successful aerial refueling. For the performance verification of the controller, a new set of nonlinear, 6-DOF, rigid body equations of motion for the receiver aircraft has been derived. The equations are developed using the reference frame as one that is attached to, translates and rotates with the tanker aircraft. Furthermore, the nonlinear equations contain the wind effect terms and their time derivatives to represent the aerodynamic coupling involved between the two aircraft. These wind terms are obtained using an averaging technique that computes the effective induced wind components and wind gradients in the receiver aircraft’s body frame. Dynamics of the engine and the actuators are also included in the study. A linear position-tracking controller has been designed using a combination of integral control and optimal LQR design. The controller does not use the information of the tanker’s vortex induced wind effects acting on the receiver aircraft as well as the mass change that occurs during refueling. The performance of the controller is evaluated in the high fidelity simulation environment employing the new sets of equations of motion. The simulation and control design are applied to a tailless fighter aircraft with innovative control effectors and thrust vectoring capability. Various allocation schemes for redundant control variables are analyzed in a realistic approach maneuver to the refueling contact position behind the tanker aircraft. In this paper, the performance evaluation is presented only during the initial phase of aerial refueling maneuver when the receiver aircraft maneuvers to reach the refueling contact position.