Model-assisted extended state observer and dynamic surface control–based trajectory tracking for quadrotors via output-feedback mechanism

In this paper, an output-feedback trajectory tracking controller for quadrotors is presented by integrating a model-assisted extended state observer (ESO) with dynamic surface control. The quadrotor dynamics are described by translational and rotational loops with lumped disturbances to promote the hierarchical control design. Then, by exploiting the structural property of the quadrotor, a model information–assisted high-order ESO that relies only on position measurements is designed to estimate not only the unmeasurable states but also the lumped disturbances in the rotational loop. In addition, to account for the problem of “explosion of complexity” inherent in hierarchical control, the output feedback–based trajectory tracking and attitude stabilization laws are respectively synthesized by utilizing dynamic surface control and the corresponding estimated signals provided by the ESO. The stability analysis is given, showing that the output-feedback trajectory tracking controller can ensure the ultimate boundedness of all signals in the closed-loop system and make the tracking errors arbitrarily small. Finally, flight simulations with respect to an 8-shaped trajectory command are performed to verify the effectiveness of the proposed scheme in obtaining the stable and accurate trajectory tracking using position measurements only.