Vision-guided autonomous landing of multirotor UAV on fixed landing marker

For most autonomous landing based on ground cooperation markers, the design of ground cooperation markers is too simple. These markers can provide position-related information when UAV is in a high position, but when UAV is in a low position, it can easily cause the UAV to lose its target and result in landing failure due to the small size of the ground marker and the narrowness of camera's field of view. To solve the above problems, this article focuses on the precise landing of UAV. An improved ground cooperation marker which can be detected in different heights is designed, a relative position coordinate system is established for pose estimation, and a height-adaptive autonomous UAV landing strategy is proposed. Simulation done in the Gazebo environment verifies that the proposed ground marker and control strategy can improve the accuracy of the vision-based autonomous landing of the UAV.