Anti-unwinding sliding mode attitude control via two modified Rodrigues parameter sets for spacecraft

In this paper, the attitude maneuver control without unwinding for rigid spacecraft is addressed based on the modified Rodrigues parameters (MRPs). First of all, an attitude control system model for rigid spacecraft is constructed by designing a selection logic for the MRP set and its shadow set. To guarantee the asymptotic stability in the large and anti-unwinding performance of the closed-loop system on the sliding phase, a sliding function is presented. Then, a sliding mode control law is presented to ensure that the system states are driven to the sliding surface. Moreover, a dynamic parameter is designed in the proposed control scheme, such that the unwinding phenomenon is avoided when the system states are outside the sliding surface. Further, a boundary layer is introduced for the presented controller to avoid the chattering phenomenon. It is also proven that the convergence property and anti-unwinding performance are ensured when the system states are within the boundary layer. Numerical simulations are performed to demonstrate the unwinding-free performance of the closed-loop system under the proposed control scheme.