Adaptive Finite-Time 6-DOF Tracking Control for Spacecraft Fly around with Input Saturation and State Constraints

An adaptive finite-time control scheme is developed for noncooperative spacecraft fly-around subject to input saturation, full-state constraints, dynamic couplings, parameter uncertainties, and disturbances. Different from traditional fly-around model based on C-W equation, the derived 6-DOF spacecraft fly-around model can be suitable for noncooperative case in close proximity. By using the backstepping control technique, an integrated adaptive finite-time control law is designed, in which the tan-type barrier Lyapunov function (BLF) is incorporated to handle the full-state constraints. Meanwhile, the unknown dynamic couplings, parameter uncertainties, and disturbances are attenuated effectively by using adaptive estimation technique and the adverse effects raised from input saturation are reduced by the designed saturation compensator. Based on the constructed BLF, it is shown that the designed adaptive finite-time controller can guarantee that full-state constraints are not breached, but also can drive relative position and attitude tracking errors into the accurate convergent regions with finite-time convergence. Finally, the performance and advantage of the designed adaptive finite-time control scheme are demonstrated by numerical simulations.