Nonlinear observer-based visual control of a VTOL UAV

This paper considers the question of fully image based visual servo control for a Vertical Takeoff and landing (VTOL) Unmanned Aerial Vehicle. A new visual feature based on the combination of the first order un-normalized spherical moment and the image length of the target image constellation is proposed. To avoid the lack of the translational velocity measurement of the camera, we propose a nonlinear observer-based visual servo controller. Compared with earlier works, the observer-based visual servo controller allows to simplify measurement through observation techniques and provides a framework to implement algorithms to stabilize an UAV in front of an unknown target. The corresponding control algorithm is presented and simulation results are finally shown to illustrate performances of the proposed approach.