Je Hyeon Lee

Graduation Semester and Year




Document Type


Degree Name

Doctor of Philosophy in Aerospace Engineering


Mechanical and Aerospace Engineering

First Advisor

Atilla Dogan


When a tanker and receiver aircraft fly in tight formation in an aerial refueling operation, they are exposed to various sources of wind with varying magnitude and direction. The tanker and the receiver aircraft experience prevailing wind and turbulence. The receiver aircraft is also subject to an additional wind field induced by the wake of the tanker.The receiver aircraft is required to fly in a precise trajectory relative to the tanker. Especially, the receiver aircraft should stay at a position with small tolerances for the fuel transfer operation while the tanker aircraft flies straight level and makes constant altitude turns. To improve the trajectory tracking and the station keeping performance of the receiver under measurement noise, the estimation of the receiver states and some of the tanker states are needed in the trajectory-tracking controller. This research has shown that the estimation of the wind exposure should be known for a successful implementation of an estimator for the states of the aircraft.A Square-Root Unscented Kalman Filter is developed for each aircraft based on their nonlinear equations of motion augmented with equations representing the effect of the wind on the aircraft dynamics. The estimation algorithms are evaluated in an integrated simulation environment that includes full 6-DOF nonlinear equations of motion of each aircraft, the controllers for each aircraft, models for prevailing wind, turbulence and vortex-induced wind as well as the aerodynamic interference on the receiver dynamics. A parameter study is used to evaluate the performance of the estimation algorithm under either white measurement noise or colored measurement noise.


Aerospace Engineering | Engineering | Mechanical Engineering


Degree granted by The University of Texas at Arlington