Position control for a class of vehicles in SE(3)

A hierarchical design framework is presented to control the position of a class of vehicles in SE(3) that are propelled by a thrust vector along a single body axis and incorporate some mechanism to induce torques about all body axes. A position control outer loop provides reference signals for an attitude control inner loop. The main result of this paper is a set of conditions under which a position controller designed for a point-mass system and an attitude controller can be combined to form a position controller that almost globally asymptotically stabilizes the vehicle to a desired position with desired heading. As opposed to the classical backstepping framework, the proposed approach is modular, in that position control and attitude control designs are completely separate. Thus, for instance, with the proposed technique one can employ any attitude controller from the vast literature on attitude stabilization, provided it enjoys a basic almost global stability property.