Autonomous assembly of multiple flexible spacecraft using RRT* algorithm and input shaping technique

The on-orbit assembly is an appealing method to build large space structures. To improve the assembly efficiency, each module trends towards a flexible one. How to account for the nonlinear rigid-flexible dynamics is still an open problem during the assembly mission. This paper presents the dynamics modeling, path planning and controller design for the autonomous assembly of multiple flexible spacecraft. Both the one-by-one and simultaneous assembly scenarios are considered. The assumed modes method is adopted to describe the nonlinear dynamic behaviors of the spacecraft equipped with six flexible appendages. The input shaping technique is used to shape the trajectory planned by the RRT* algorithm to reduce the vibrations of flexible appendages caused by the trajectory tracking for each spacecraft. To avoid collisions among the spacecraft in the team and obstacles, a PD controller together with collision avoidance forces is proposed to drive the spacecraft to track their desired trajectories. Finally, some numerical results are presented to show the effectiveness of the developed path planning algorithm and controller design method. The main major finding of this paper is that the introduction of input shaping technique can reduce the vibration caused by the collision-free trajectory from the RRT* algorithm in assembly mission.