Visual Servoing for Underactuated VTOL UAVs : a Linear, Homography-Based Framework

The paper concerns the control of Vertical Take Off and Landing (VTOL) Underactuated Aerial Vehicles (UAVs) in hover flight, based on measurements provided by an on-board video camera. The objective is to stabilize the vehicle to the equilibrium pose associated with an image of a planar target, using a minimal sensor suite and poor knowledge of the environment. By using the homography matrix computed from the camera measurements of the target, stabilizing feedback laws are derived based on the visual data and gyrometer measurements only. Explicit stability conditions on the control parameters are provided, showing that a proper tuning of the control parameters ensures a large robustness margin with only planar target and visibility assumptions, while the target size and orientation, the UAV position, linear velocity and orientation are unknown. Additional issues, such as the use of accelerometers in order to improve the UAV’s positioning in the case of unmodeled dynamics (like wind), are also considered.