Laser-based guidance of a quadrotor uav for precise landing on an inclined surface

This paper is focused on measurement and control schemes for a quadrotor UAV to precisely land on a flat inclined surface without prior knowledge of the surface´s orientation. Assuming that the location of the landing site is known, a quadrotor performs a flyover and uses lasers and a CMOS camera to detect the projections of the lasers on the ground plane to measure the relative ground plane angle of the landing site. This information is then used to design an aggressive landing trajectory such that the quadrotor touches down parallel to the landing surface. During the initial phase of the maneuver, a trajectory-tracking controller guides the quadrotor, and as it nears the landing phase, an attitude-tracking controller ensures that the attitude of the quadrotor matches the slope of the landing platform upon touchdown. This approach is illustrated by numerical examples and preliminary experimental results for laser-based surface angle determination.