充液挠性航天器姿态机动终端滑模控制

Research on Attitude Maneuver and Vibration of Liquid-filled Flexible Spacecraft Based on Terminal Sliding Mode Control

对存在未知外界干扰、参数不确定问题的刚–液–柔多体耦合航天器姿态控制进行了研究。将液体燃料的晃动等效为球摆模型,挠性附件假设为欧拉–伯努利梁,运用拉格朗日方法建立航天器的动力学方程。将外界干扰、航天器转动惯量的参数不确定性以及液体晃动和挠性附件振动带来的耦合干扰归结为集总干扰,设计干扰观测器对其进行补偿;在干扰观测器的基础上,设计一种模糊滑模控制律。在原有的终端滑模控制基础上采用模糊控制对切换增益进行改进,达到抑制系统抖动的目的。数值仿真结果表明:所设计的模糊终端滑模控制律不仅能够实现充液挠性航天器的姿态机动,而且能够有效抑制液体晃动和挠性附件的振动,具有更好的控制性能。

In this paper,the attitude control of rigid-liquid-flexible multi-body coupling spacecraft with unknown external disturbances and uncertain inertia parameters is studied,and an attitude maneuver control method based on disturbance observer and fuzzy terminal sliding mode control is proposed.The sloshing of liquid fuel in the spacecraft is equivalent to a spherical pendulum model,and the flexible appendages are assumed to be an Euler-Bernoulli beam.The coupled dynamic equation of the liquid-filled flexible spacecraft is derived by using the Lagrange method.First of all,the interference from space,the parameter uncertainty of the moment of inertia of the spacecraft,the coupling interference caused by the liquid sloshing and the vibration of flexible accessories are summed up as lumped interference.Design disturbance observer to compensate and estimate the lumped disturbance of the system.Then,based on the designed disturbance observer,a fuzzy terminal sliding mode control law is presented,and it is proved that the state of the closed-loop system is finite-time stable under the control law,and converges to the specified terminal sliding mode surface.The fuzzy terminal sliding mode control law uses fuzzy control to improve the switching gain based on the traditional terminal sliding mode control to achieve the purpose of suppressing system jitter.This optimization method can not only reduce the complexity of terminal sliding mode control method,but also reduce the difficulty of debugging parameters because it does not introduce new functions.The numerical simulation results show that the designed fuzzy terminal sliding mode control law can not only achieve the finite-time stability of the closed-loop attitude control system of the liquid-filled flexible spacecraft,but also effectively suppress the liquid sloshing and the vibration of the flexible appendages.At the same time,it has good robustness to disturbances caused by external disturbances and parameter uncertainties,and has better control performance.