Robust output tracking control of VTOL aircraft without velocity measurements ⋆

In this paper, we develop a nonlinear controller to achieve causal output tracking for a non-minimum phase vertical take-off and landing (VTOL) aircraft without velocity measurements. Due to the presence of disturbances, auxiliary control inputs are introduced in the state observer to attenuate their effects. By decomposing the original system into one minimum phase and one non-minimum phase subsystems, the corresponding sub-control laws are respectively designed. After control transformation, the resulting controller not only forces the VTOL aircraft to asymptotically track the desired trajectories, but also drives the unstable internal dynamics to follow the causal ideal internal dynamics solved via stable system center method. Numerical simulation results illustrate the effectiveness of the proposed controller.