This article addresses the problem of velocity‐free fixed‐time attitude cooperative control for multiple spacecraft under directed communication graphs and in the presence of bounded disturbances. A distributed fixed‐time state observer is designed to estimate the leader's attitude states and a fixed‐time extended‐state observer is presented to obtain accurate estimates of both unmeasurable angular velocities and bounded disturbances. By use of the fixed‐time observers, a distributed fixed‐time attitude cooperative control scheme is proposed to make the states of all spacecraft simultaneously track a time‐varying reference attitude even when the reference attitude is available only to a subset of the group members. Homogeneous Lyapunov function and homogeneity property are applied to demonstrate that the control scheme can guarantee the attitude tracking errors converging to the neighborhood of the origin in fixed time which is independent of initial conditions. Finally, numerical simulations are presented to show the effectiveness of the control law derived here.

中文翻译：

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有向图下航天器编队的无速度固定时间姿态协同控制

本文针对有向通信图和存在有界干扰的情况，解决了多航天器的无速度固定时间姿态协作控制问题。设计了一个分布式的固定时间状态观测器来估计领导者的姿态状态，并提出了一个固定时间扩展状态观测器来获得对不可测量的角速度和边界干扰的精确估计。通过使用固定时间观测器，提出了一种分布式固定时间姿态协作控制方案，以使所有航天器的状态同时跟踪随时间变化的参考姿态，即使该参考姿态仅可用于组成员的子集时也是如此。 。应用齐次Lyapunov函数和同质性证明了该控制方案可以保证姿态跟踪误差在固定时间内收敛于原点附近，而不受初始条件的影响。最后，通过数值仿真表明了此处导出的控制律的有效性。