ESO-based nonlinear flying boom attitude control with the handling qualities requirement

Attitude control is an important component of the flying boom system and plays a key role in air-to-air refuelling. A flying boom attitude control task is usually constituted by two subtasks. The first is to reject disturbances in the flight environment, and the second is to enhance handling qualities so that the flying boom can be efficiently and safely navigated into the refuelling receptacle by the boom operator. This paper presents a novel extended state observer (ESO)-based nonlinear flying boom attitude controller design method. To solve the first subtask, the ESO is introduced to estimate the disturbances and uncertainties of the flying boom. Based on the estimation, a nonlinear feedback controller is designed to reject the disturbances in real time. With the support of Lyapunov stability criteria, it is proved that the desired attitude trajectories can be bounded tracked by the flying boom under the proposed controller and the closed-loop dynamics of the system converge to a second-order reference model. To solve the second subtask, the parameters of the reference model are selected with desired handling qualities based on a handling qualities criterion of the flying boom. With the proposed controller, the flying boom system can have both high tracking performance and desired handling qualities. Comparisons among the proposed method and the related methods are simulated to reveal that the proposed method performs better in terms of tracking performance and robustness. Besides, a series of experiments are made on a simulator to validate that the proposed controller can achieve the desired handling qualities.