充液航天器的鲁棒固定时间终端滑模容错控制

本文以三轴稳定充液航天器为研究背景,在其进行姿态机动控制过程中充分考虑了外部未知干扰、参数不确定、执行器故障和控制输入饱和等因素的影响,提出了一种固定时间终端滑模控制策略.动力学建模过程中,利用粘性球摆等效力学模型模拟液体燃料小幅晃动,通过拉格朗日方程推导出航天器的耦合动力学模型.姿态控制器设计过程中,首先构造固定时间滑模面,使其稳定到平衡位置的时间与系统初始状态无关.然后采用固定时间控制理论结合自适应估计算法提出了自适应固定时间容错控制律,其中自适应算法用于估计系统集总扰动的未知上界.所提出的控制策略采用饱和函数克服终端滑模控制方案中存在的奇异性问题,同时保证系统状态快速收敛到固定时间滑模面.根据Lyapunov稳定性理论证明了系统状态能够在固定时间内收敛到原点的较小邻域内.对比的数值仿真方法验证了本文提出控制方法的有效性和鲁棒性.

Robust fixed-time terminal sliding mode fault tolerant control for liquid-filled spacecraft

In this paper,the fixed-time robust fault tolerant control strategy is proposed for attitude maneuver control system of liquid filled spacecraft with unknown external disturbances,uncertain parameters,actuator faults and control input saturation.In the process of dynamic modeling,the liquid fuel sloshing is equivalent to a viscous spherical model,and the coupling dynamic model of spacecraft is deduced by the Lagrangian formulation.In the process of attitude controller design,a fixed time sliding surface manifold is constructed firstly so that the settling time of the surface manifold is independent of system’s initial states.Then,an adaptive fixed time sliding mode control law is designed combined with the fixed time control method and adaptive estimation algorithm,in which the adaptive algorithm is used to estimate the unknown upper bound of the lumped disturbances.The proposed control algorithm uses the saturation function to overcome the singularity problem in the terminal sliding mode control method,and it can shorten the convergence time during the system state reach the sliding surface.Lyapunov stability analysis theory proves that the state of closed-loop system converges to small neighborhood of the origin in fixed time.The comparative simulation results show the effectiveness and robustness of the proposed control method.