Anti-unwinding Robust Adaptive Sliding Mode Attitude Control for Rigid Spacecraft

Reliable spacecraft attitude control during maneuvers is essential for the success of space missions. This paper introduces a robust adaptive control strategy for rigid spacecraft attitude tracking capable of dynamically adjusting control system parameters to respond to inherent parametric uncertainties and external disturbances. The primary objective is to ensure the convergence of unit quaternion-based spacecraft system states in the presence of inertial uncertainties and disturbances while avoiding unwinding phenomena. The proposed method uses a switching function designed to drive the error trajectories of rigid spacecraft onto a sliding manifold containing two equilibria. Subsequently, a robust adaptive attitude tracking control is developed to handle uncertainties and disturbances while driving the system error states toward the origin along the sliding surface. In consideration of safe actuator operation, the chattering phenomenon is minimized by utilizing a boundary layer function. Constraint is employed on the designed parameters of the adaptive function in such a way that the system states converge within this boundary layer. The Lyapunov stability theory demonstrates the stability analysis of the attitude control system for rigid spacecraft. Numerical simulations validate the effectiveness, reliability, and anti-unwinding capabilities of the proposed approach.