Finite-time 6-DOF tracking control for rigid spacecraft with relative velocity constraints

This paper investigates the finite-time six-degree-of-freedom tracking control problem for the rigid spacecraft system with relative velocities soft constraints and external disturbances. Magnitude constraints of both translational velocity and angular velocity are simultaneously considered in the integrated attitude-position control law for the first time. The relative spacecraft model and the corresponding design process are performed in the dual quaternion framework due to its compact form and excellent properties. A feedback pose tracking control law is first presented with bounded velocities constraints based on the potential function methods, and finite-time convergence of the system under this controller is established using the homogeneity theorem. Then, combined with a specially designed integral sliding mode and a finite-time disturbance observer, an improved finite-time robust pose control law is further proposed in the presence of external disturbances. At last, numerical simulations verify that the proposed control law not only achieves finite-time convergence under velocity constraints, but also exhibits disturbance rejection capability.