关键词: 无人艇, 协同定位, 单目视觉, 合作标志, 地下封闭水体

Abstract: Abstract: Aiming at the problems of lack of satellite positioning signal, limited communication and weak ambient light in subterranean confined water body, a cooperative visual localization method of multiple Unmanned Surface Vehicles (USV) in subterranean confined water body was proposed in this paper. Firstly, a vehicles-borne light cooperative markers was designed, and the markers structure was optimized according to the vehicle structure and application scene. Secondly, monocular vision was used to collect the markers image and obtain the image coordinates of the feature points. Next, on the basis of camera imaging model, by using the relationship between the coordinates of the marker in the marker coordinate frame and the coordinates of the corresponding feature points of the markers in the image coordinate frame, and the relative pose between adjacent vehicles was calculated by improved direct linear transform method. Then, the cameras of the front and rear vehicles were used to view each other between the vehicles. Through the minimum variance algorithm, the relative positions calculated based on the images of the front and rear vehicles were fused to improve the relative positioning accuracy. Finally, the absolute location of each USV was obtained by using the known absolute coordinates in the scene. In this paper, the factors affecting positioning error are analyzed through simulation experiments, and compared with the traditional direct linear transformation method. As the distance increases, the effect of this method becomes more obvious. At a distance of 15m, the position variance solved is stable within 0.2m2, verifying the accuracy of this method. Static experiments show that the method in this paper can stabilize the relative error within 10.0%; through dynamic experiments in underground rivers, the absolute positioning navigation trajectory is solved, achieving an accuracy comparable to satellite positioning, which verifies the feasibility of this method.

Key words: Unmanned Surface Vehicle (USV), cooperative localization, monocular vision, cooperative markers, subterranean confined water body