Admissible thrust control laws for quadrotor position tracking

In this paper a hierarchical position tracking controller for a quadrotor is presented, which consists of an inner attitude controller and an outer position controller. The tracking error dynamics form a nonautonomous cascade built up by a linear attitude error subsystem and a linear position error subsystem, coupled by a nonlinear interconnection term. The stability properties of the cascaded system essentially rely on the characteristics of the interconnection term, which strongly depends on the choice of the thrust. We characterize a class of admissible thrust control laws in terms of closed loop asymptotic stability and demonstrate the significant influence of different laws on the transient behavior of the system.