Autonomous air-to-air refueling : a comparison of control strategies

[摘要] ENGLISH ABSTRACT:The air-to-air refuelling of large aircraft presents challenges such as a long fuel transfertime, slow aircraft responses and a large distance between the aircraft CG and thereceptacle position. This project addresses some of these issues by adding a controlsystem to keep the receiver aircraft in the correct position relative to the tanker toenable fuel transfer.This project investigates different control strategies which are designed to control theA330-300 during refuelling at one trim condition. The controllers are based on a mathematicalaircraft model which was derived from a simulation model received fromAirbus.The first set of controllers uses the aircraft actuators directly. Controllers that arebased on the CG dynamics and the receptacle dynamics are compared. Due to the largedistance between the CG and the receptacle it was found to be essential to control thereceptacle position, and not only the CG position. Also, a controller that is based on amodel of the receptacle dynamics performs better.The second set of controllers uses the aircraft manual control laws as an inner loopcontroller. This set of controllers and the last direct actuator controller use the sameaxial controller that uses the engine thrust to control axial position.It was found that both the direct actuator controller and the manual control lawscontroller are able to keep the receptacle within the disconnect envelope in moderateturbulence. In both sets of controllers the axial controller fails to keep the receptaclereliably within the disconnect envelope in light turbulence.From the results it is concluded that both the direct actuator control and manual controllaws can be used to successfully control the receptacle position in the normal and lateralpositions as long as the receptacle kinematics are included in the control design. Usingonly the engine thrust for axial control is insufficient. Several recommendations aremade to improve the axial control and also how these results can be used in futurework.

[发布机构] Stellenbosch University