Research On Relative Position Measurement Of Non-cooperative Spacecraft

With the development of space technology, the space was explored more andmore in-depth by human. At the same time, the problems were also became moreand more complex, which put forward higher requirements for space technology.With the frequent aerospace activities, a large amount of space junks and failuresatellites were produced. To repair failure satellites and clean-up space junks havebecome a serious problem that the space powers must face. In this context, peoplesput forward the on-orbit service technology under the purpose of repair failuresatellite and clean-up space junks. Measurement of the relative position andorientation of the spacecraft is the premise of the operations that to tracking close,grab, maintenance etc. Most of the failure satellites and space junks haven’t installthe signs of auxiliary measurements, So they are non-cooperative targets. The onorbit failure satellites will be main object to study in this article. Non-cooperativespacecraft relative pose measurement method will be studied in the double robotground experimental system.The camera calibration of the double robot ground experimental system hasbeen studied. In order to get accurate calculation results, the intrinsic parameters andthe external parameters of the camera need to be learn. The intrinsic parameters andthe relative pose between camera and checkerboard can be calculated directly byplane calibration method. The laser tracker was used to get the relative pose of thecheckerboard and the robot end. Then the camera installation pose of the robot endcan be converted. This is the camera external parameters.According to the characteristics of the space environment, the imageprocessing is studied. Several typical image filtering method are analyzed. Thethreshold setting problem solved by using the adaptive Canny algorithm. The ellipseparameters got by the algebraic distance ellipse fitting, A autonomous method basedon the structural characteristics of the target is researched.A relative pose calculation method is studied for circular characteristics.Analysis the direction of circular features. Binocular stereo vision measurementmodel is built. the center position and direction of circular characteristics arecalculated by using the ellipse parameter.Use the double robots ground experimental platform to verification themeasurement method. In order to improve the efficiency of the experiment, save theexperiment cost, prevent equipment loss caused by error operation, an digitalsimulation system based on OSG is established. The control and measurementalgorithms are confirmed in the digital simulation system. Then use double robots ground experimental platform to verification the reliability and accuracy of thealgorithm. Proved by experiments, the measurement method based on binocularstereo vision is a stable and effective measuring method, can meet the requirementof GNC.In this article the whole process of vision measurement method are detailedresearched. And made a Ground experiments. It has greater value of practicalapplication for visual measurement methods.