Fixed-Time Robust Networked Observers and Its Application to Attitude Synchronization of Spacecraft Systems

This article studies fixed-time robust networked observers to estimate the information of a leader system containing unknown parameters. The construction of observers combines the internal model principle and the fixed-time control technique in a network with a directed topology. The observers are further applied to the fixed-time attitude synchronization problem for multiple spacecraft systems whose attitudes are represented by unit quaternion. Both rigorous analysis and numerical simulation demonstrate that the fixed-time synchronization of attitude and angular velocity between multiple spacecrafts and a specified leader system is achieved by the observer-based control design.