Norm-approximation-based adaptive fuzzy control for 6-DOF spacecraft rendezvous and docking

This study focuses on the 6-DOF (six degrees of freedom) relative translation-rotation coupled control problem for spacecraft autonomous rendezvous and docking. The impacts of unknown inertial characters, space perturbation forces, and moments are considered. First, the integrated 6-DOF position-attitude coupled motion model is built up in the body-fixed frame of the active spacecraft. Then, an adaptive fuzzy control approach is developed by using the backstepping method, which estimates the lumped perturbation of the dynamics model uncertainties through the fuzzy approximation principle. Meanwhile, the norm approximation technique is utilized to decrease the consumption of computational resources caused by excessive online parameters in traditional fuzzy approximation methods. This method uses norm-mapped parameters to replace the adaptive parameters in traditional fuzzy logic systems, thereby approximating the total system disturbances with a reduced number of parameters. The results of the simulation experiment show that the developed method can achieve the rendezvous and docking objective disturbances and uncertainties.