The Vision Measurement For Spacecraft Position And Attitude Determination In The Phase Of Final Approaching For Rendezvous And Docking

The technology of the vision measurement for spacecraft position and attitude determination in the final approaching phase of rendezvous and docking is a hot topic in research for each big country and organization of space technology. It is also a multidisciplinary and integrated technology. This thesis comes from a pre-research project on civilian space, and it makes an in-depth discussion of the technology of the vision measurement for spacecraft position and attitude determination in the final approaching phase of rendezvous and docking, including the research based on the model of stereo camera vision for spacecraft position and attitude determination, the research on algorithm of feature extracting for image processing, the research on designing method for spacecraft feature points, the research on the matching method for spacecraft feature points, and the designing of experiment system, etc.The main contents and conclusions of this paper are expressed in the following aspects:1.In this paper, we established the mathematical model of vision measurement system based on stereo camera vision, and derived the transformation relationship between two-dimensional image coordinates to Three-dimensional world coordinates. Based on the actual situation, this paper established a simple abstract mathematical model for complex spacecraft system, through the establishment of spacecraft body coordinates. Determined the center of the solar battery panels'connecting axis of the spacecraft as the parameter of the spacecraft position determination; the three rotation angles, that the spacecraft body coordinates roll around three different coordinate axis of the world coordinates, as the parameter of the spacecraft attitude determination.2.An in-depth discussion on algorithm of feature extracting for image processing is made. Including"canny"edge detection, line detection circle and ellipse detection based on"Hough Transform". As while as the morphological processing method of gray-scale image, including dilates, erode, gradient, etc. The experiment results show that the feature line and feature ellipse can be detected accurately, and it can also provide the parameter of the feature line and feature ellipse.3.According to the backgrounds of the vision measurement for spacecraft position and attitude determination in the final approaching phase of rendezvous and docking, we established two independent feature systems, which contain the solar battery panels feature plane and the spaceship cabin front surface feature plane. And rationally designed feature points on the two feature planes. Based on the design specialty of the feature points, this paper established a feature points extraction method, that is depend on"three baselines on the solar battery panels feature plane"and"the feature circle on the spaceship cabin front surface feature plane", and a feature points matching strategy that depend on"grouping by three baselines and guiding by six base points". 4.Based on the motion control platform, the experiment system is established, and determines the experimental program. Static and dynamic experiments are made. According to the analysis of the results of experiments and the three-dimensional reconstruction and recovery of the feature points, the experiment result shows that the coordinates repeatability precision is better than 0.2mm, and the angle repeatability precision is better than 0.01°when the spacecraft staying in the same position. The distance measurement accuracy is better than 0.4mm and the angle measurement accuracy is better than 0.2°when the spacecraft model moving along three coordinate axis. This shows that the description of the spacecraft position and attitude determination is feasible. Finally, the error factors in the experiment system are analyzed, and put forward some measures to reduce the error.