Research And Implementation Of Vision-Based Measurement Method For Space Rendezvous And Docking

Space rendezvous and docking (RVD) measurement technology is the key technology in RVD. It decides the success of the rendezvous and docking processing. Visual measurement technology based on CCD camera is a hot topic at present. In this paper, a system study on vision-based measurement in RVD is developed though designing and building the simulation measurement system and developing the measurement algorithm. An in-depth study on the key technology including image feature extraction and posture measurement is developed.The image feature extraction technology decides the precision of the vision-based measurement. In this paper, feature signs are circular and the projected images are ellipses. In consider of actual application, two extraction methods for ellipse center points are designed according to the distance of the two aircrafts. One method gets the center point by calculating the barycenter of the image gray. It is used when the two aircrafts are in a far distance. The other method gets the edge of the ellipses with edge detection technology, then, gets the center point by ellipse least square fitting. It is used in the near distance. In this way, the accuracy is guaranteed as well as the computational efficiency. Effectiveness of absolute difference mask algorithm is verified through simulation experiment compared with canny operator.In consideration of actual application, posture measurement method with a single camera is well studied. The liner algorithms according to different corresponding points are discussed. Two methods are proposed. One solves the posture using 2D-3D point correspondence. The other gets the coordinates of the points in camera coordinates though solving the PNP problem first, then, gets the posture with a simple method. The actual system completes the measurement with just three circular features according to the study above.The simulation vision-based measurement system is designed and built. The vision-based measurement algorithm is developed, including the high precise camera calibration algorithm. A measurement method for the precision of the system with API instrument is designed. The result of the measurement indicates that the precise satisfies the requests for application.