Time-Synchronized Tracking Control for 6-DOF Spacecraft in Rendezvous and Docking

For the short-rangerelative motion of the on-orbit service spacecraft during rendezvous and docking missions, this article improves control performance with the describable straight line convergence trajectory and reduces energy consumption by proposing and solving the spacecraft time-synchronized control problem. This problem requires that the closed-loop system of the spacecraft is finite/fixed-time stable, all nonzero elements converge synchronously, and the trajectory of the closed-loop system tends to be the describable straight line. Based on the time-synchronized stability (TSS) and fixed-time-synchronized stability (FTSS), this article proposes the TSS and FTSS controllers for the 6-degree of freedom (DOF) spacecraft to solve the problem. For the spacecraft closed-loop system under these optimization-free methods, the derivative of the state is always opposite to the direction of the state, then the system trajectory will tend to a straight line, and the redundant motion components in the direction orthogonal to the state are significantly suppressed (performance improvement), and the excess energy loss is reduced considerably. Conversely, redundant motion components will cause excess transient motion and more energy consumption. Furthermore, this article proposes the linear combination theorem of the ratio persistence property, which further enriches the theoretical tools for the time-synchronized control method. The rigorous theoretical proof and comparative simulation verify the rationality, effectiveness, and advantages of the controllers proposed.