Circular Drogue Pose Estimation for Vision-based Navigation in Autonomous Aerial Refueling

This paper presents a new vision pose estimation method based on the circular feature, and the method is applied in the autonomous aerial refueling to solve the drogue pose estimation problem by using the internal circular refueling port of drogue as the vision feature. Any optical marker on the refueling drogue is not required. In the proposed circular pose estimation method, the oblique conical surface equations in the camera frame and world frame are established respectively, and the constraint condition that rotation transformation doesn't change the eigenvalues of coefficient matrixes is used to solve the unknown parameters, including the coordinate of circle center and the unit normal vector of circle plane. The visual simulation test and ground test are designed and done. Results show that the proposed method has the plane position error below 2cm when the relative distance is below 8m in the visual simulation test, and has the relative distance error less than 6% in 94.71% of cases in the ground test. The proposed method is able to meet the requirements of the positioning accuracy in the autonomous aerial refueling procedure.