Receptacle normal position control for automated aerial refueling

Novel flight control laws are presented for the receiver aircraft during aerial refueling. The case of a large transport aircraft refueling a similarly sized aircraft is investigated. The controller focuses on the normal position of the receiver aircraftʼs refueling receptacle during automated aerial refueling. Specifically the effect of the relatively long distance between the receiver aircraftʼs center of gravity and the refueling receptacle is analyzed. An existing linear aircraft model is adapted to describe the dynamics from the perspective of the refueling receptacle on the receiver aircraft. It is found that the receptacle dynamics contain a complex pair of zeroes in the left half of the S-plane. Three possible control architectures are considered. The analysis indicates that, when controlling a large receiver, the inclusion of the receptacle dynamics is essential for adequate low frequency disturbance rejection. It is found that the presence of the zeros degrade the systemʼs response when the closed loop bandwidth nears the zerosʼ frequency; effectively limiting the attainable bandwidth. A method is presented to compensate for the presence of the zeros and improve the receptacleʼs response. Suitable pole locations are chosen for all required flight points. The effect of tanker downwash uncertainties on the closed loop system is investigated. High fidelity nonlinear simulation results show that the control laws can successfully regulate the receptacle at the required points while subjected to light turbulence and expected tanker downwash.