Saturated attitude control with almost global finite-time stabilization

The problem of finite-time attitude stabilization of a rigid spacecraft is revisited. First, homogeneous system theory is utilized to design a simple proportional-derivative (PD) type saturated finite-time controller (SFTC) based on quaternion, which avoids the undesirable unwinding phenomenon. Strict proof shows that the quaternion-based SFTC ensures almost global finite-time stability of the resulting closed-loop systems. Moreover, the proposed SFTC not only yields bounded control torques, but also possesses robustness to large inertia uncertainties of the spacecraft since they are completely independent of the spacecraft inertia. Numerical results demonstrate the effectiveness and superiority of the proposed controllers.