Robust Nonlinear Control of Aerial Manipulators

This paper presents single-layer robust nonlinear controllers for the unmanned aerial manipulator (UAM) trajectory tracking problem. The multi-body dynamical modeling of an underactuated UAM is conducted from the perspective of its end-effector using the Euler-Lagrange formalism. Accordingly, two single-layer nonlinear controllers are designed based on the classic H-infinity and the novel W-infinity control approaches for robust trajectory tracking of the UAM end-effector. The nonlinear H-infinity and W-infinity controllers are implemented in a hardware-in-the-loop framework using a simulator developed on Gazebo and ROS platforms, based on the computer-aided design model of the UAM. The performance of the controllers is evaluated when executing tasks such as object grasping, extension and retraction of the manipulator arm, hovering, and tracking a time-varying trajectory, while the UAM is affected by disturbances as ground effect, environment wind, and parametric and structural uncertainties.