Position Tracking of a Multicopter Using a Geometric Backstepping Control Law
In this paper a position tracking controller for a multirotor helicopter is presented. The controller design exploits the fact that for position tracking, the control of the whole attitude is not needed,but only the control of the body-fixed z-axis. This results in a position controller which is independent of the heading controller. This is achieved by introducing the thrust vector as a system's state, i.e. using the body-fixed z-axis as a reduced attitude parameter and extending the thrust input T dynamically. This parameter choice also avoids drawbacks of local attitude parameterizations like singularities or unwinding and thus maximizes the flight envelope. The position controller is designed using a three-step backstepping control law, such that no time-scale separation is needed. Furthermore, two heading controllers are proposed.