Velocity-free attitude reorientation of a flexible spacecraft with attitude constraints

A velocity-free control law that can achieve rest-to-rest three-axis attitude reorientation with autonomous avoidance of the undesired celestial objects is presented for a flexible spacecraft, based on potential function methods. The spacecraft orientation in the presence of constraints, are formulated in terms of unit quaternion and is further parameterized to a convex set representation. Because the proposed quadratic potential function is proved to be strictly convex, it has the capability to handle multiple attitude-constrained zones and guarantee convergence toward the desired attitude.