Relative Motion Modeling and Control of Non-Centroid Contact Points of Spacecraft

The docking port of the spacecraft in rendezvous and docking is usually located on the surface of the spacecraft. It is not located in the center of mass. However, the traditional relative motion modeling often uses the spacecraft centroid as the reference point, so that the actual operation requires additional planning for the docking port, will undoubtedly reduce the efficiency of operational tasks. In this paper, based on the spin description, the relative motion modeling method between the non-centroid of spacecraft is studied. Firstly, by introducing the appropriate conversion operator, the relative velocity rotation between non-centroid pairs is established, and then the coupled model of non-centroid relative motion and attitude is deduced by using the mechanics principle and spin theory. The model not only avoids the singularity of attitude calculation, but also has the unified form of description and there is no requirement for the spacecraft control system, which is conducive to collaborative controllers design. Based on this model, considering the influence of spatial perturbation and unknown disturbance, this paper designs a control law combining nonlinear feedback control and PD control based on logarithm of state deviation logarithm, and proves the stability and completes the simulation. The results show that the proposed method is feasible and has good control effect, and the docking state of the docking port can be realized accurately, which provides a theoretical reference for coupling modelling of space relative motion and the design of the coordinated control system.