Disturbance observer-based control of UAVs with prescribed performance

This work proposes a novel robust nonlinear control method for trajectory tracking of a quadrotor unmanned aerial vehicle using the prescribed performance control technique and disturbance observers, in the presence of external disturbances and uncertainties of physical parameters. By exploiting the cascaded structure of the position subsystems and the attitude subsystems, the controller is designed in a backstepping manner, and the dynamic surface technique is adopted to avoid the explosion of the controller complexity. For each axis of the subsystem with uncertainties, the prescribed performance control technique is adopted to ensure a moderate control performance. Then a disturbance observer is constructed to enhance the corresponding controller to achieve a sufficiently small ultimate error. Not only the control performance of the overall control system, but also the behaviour of all the internal error signals are analysed rigorously. Finally, the performance of the proposed controller is confirmed by simulation studies.