Simple finite-time attitude stabilization laws for rigid spacecraft with bounded inputs

The problem of finite-time attitude stabilization of a rigid spacecraft is investigated. Homogeneous system theory is utilized to design a simple nonlinear proportional-derivative-type (PD-type) saturated finite-time controller (SFTC), which can accommodate its form to different attitude parameterizations, such as quaternion, Rodrigues parameters (RP) and modified Rodrigues parameters (MRP). The proposed SFTC is inertia-independent and yields bounded control torques, in addition to finite-time convergence. Specially, the quaternion-based SFTC avoids the unwinding phenomenon associated with traditional continuous quaternion-based control laws and achieves, as shown by the MonteCarlo analysis, a faster convergence than a previous quaternion-based finite-time attitude stabilization law. Numerical examples are presented to verify the efficacy of the proposed method.