Research On Vision-Based Autonomous Landing Of An Unmanned Aerial Vehicle

Autonomous landing is a key capability in the autonomy of UAV. It is a major direction of development to accurately achieve self-landed based on the vision system.The paper presents a real-time algorithm of identifying landing pad and estimating the state information for landing an unmanned aerial helicopter on a given landmark automatically. The algorithm estimates the instantaneous attitude and position parameters of the helicopter relative to the landing pad from continuously tracking over feature points in consecutive frames using a calibrated monocular camera. The design of this vision system mainly performs image processing, landmark recognition, feature extraction, target tracking and motion estimation. Tracking algorithm is based on the Lucas-Kanade optical flow tracking method, and the orientation, provided by an inertial measurement unit, refines the computed attitude. The proposed algorithms are simulated on a model platform indoors in the laboratory conditions for the preliminary checking. Monocular experimental demonstrate that the algorithms can achieve real-time operation, and that the results are reliable within the range of error tolerance.Given the circumstances of emergency, a method is proposed to select a safe landing area without prior knowledge of the environments. The structure of three-dimensional scene information is reconstructed using the image information retrieval based on binocular vision system. And the scene of the plane information is calculated, combining with the requirements of landing:flat, slope, area, and surface characteristics. The calibration of stereo vision system, the distortion correction, the level of polar correction, stereo matching, and three-dimensional scene structure recovery algorithm are discussed in order to achieve the fast processing speed. After repeatedly confirmed the safety of the decided region, select the invariants to establish the fixed ground coordinate system from the camera coordinate system. It can aid the UAV successfully landing in an unknown environment through feature tracking to determine the position and orientation of UAV relative to the security zone.