This article investigates the problem of distributed fixed-time attitude consensus control for multiple spacecraft when only a subset of spacecraft has access to a common reference attitude and angular velocity. Two fixed-time sliding-mode observers are proposed to estimate the reference attitude and angular velocity in fixed time, respectively. Based on estimates of the reference attitude and angular velocity, two distributed fixed-time attitude consensus control schemes are proposed under the mild assumption that there exists a path from the virtual leader to any follower and the communication topology among followers is undirected. In the first control scheme, the measurement of angular velocity is required. However, this requirement is removed in the second control scheme by using a fixed-time state observer to estimate the angular velocity of spacecraft in fixed time. Only a subset of spacecraft is required to access a common reference attitude and angular velocity in the two proposed control schemes. The stability and convergence of the resulting closed-loop systems are guaranteed by the Lyapunov approach. Finally, simulation results validate the effectiveness of the proposed control schemes.

中文翻译：

---

开放区域中的超宽带空对地传播信道特性

本文研究了当只有一个航天器子集可以访问公共参考姿态和角速度时，多个航天器的分布式固定时间姿态一致性控制问题。提出了两个固定时间滑模观测器来分别估计固定时间的参考姿态和角速度。基于对参考姿态和角速度的估计，在假设存在从虚拟领导者到任何追随者的路径并且追随者之间的通信拓扑是无向的情况下，提出了两种分布式固定时间姿态一致性控制方案。在第一种控制方案中，需要测量角速度。然而，在第二种控制方案中，通过使用固定时间状态观测器来估计航天器在固定时间内的角速度，这个要求被取消了。在两种建议的控制方案中，只需要航天器的一个子集来访问共同的参考姿态和角速度。Lyapunov 方法保证了所得闭环系统的稳定性和收敛性。最后，仿真结果验证了所提出的控制方案的有效性。