Research On Close Range Pose Measurement Of Space Non-cooperative Target Based On The ToF Camera

With the development of space technology,the demand for space on-orbit services is becoming increasingly urgent.As a critical technology of on-orbit service,the pose measurement of space non-cooperative targets in close-range has received widespread attention.The commonly used space pose measurement load is the visible light camera.However,the imaging quality of the visible light camera is greatly affected by the space lighting environment.It will result in poor accuracy and robustness of non-cooperative target pose measurement based on the visible light image.The Time of Flight(ToF)camera is not sensitive to ambient light.It has the advantage of obtaining intensity and depth images simultaneously,provides a new measurement method for the pose measurement of non-cooperative targets in space close-range.At present,the pose measurement method based on the ToF camera still has some problems,such as the low accuracy of the existing imaging simulation data,which is challenging to meet the algorithm test requirements,the low utilization of the camera measurement data by the traditional 3D reconstruction method,which results in poor reconstruction accuracy,the pose measurement method is sensitive to the point cloud noise and has high requirements fo r the initial value accuracy of the pose.Therefore,facing the demand for on-orbit service applications,it is urgent to research the close-range pose measurement technology of space non-cooperative targets based on the ToF camera,which has important theoretical significance and application value for the improvement of our on-orbit service capability in the future.Aiming at the problem of low accuracy of traditional ToF imaging simulation method,the research on the physics-based ToF imaging simulation method of space targets has been deeply carried out.Based on the analysis of ToF camera imaging characteristics and the research on the measurement and modeling results of typical space target surface material characteristics,a space target ToF imaging si mulation method based on ray tracing is proposed,the ray tracing mathematical model of ToF camera is theoretically deduced and the ToF camera full-link imaging simulation model that comprehensively considers the influence characteristics of all aspects of signal transmission is constructed,realizes the physics-based space target ToF imaging simulation,and improves the ToF imaging simulation accuracy.It provides reliable input data for the subsequent development of the space non-cooperative target pose measurement algorithm based on ToF camera.Aiming at the problem that the traditional 3D reconstruction method of non-cooperative target based on the ToF camera has low reconstruction accuracy due to the low utilization of the ToF camera measurement data,the research on the reconstruction method of spatial non-cooperative target point cloud based on the fusion feature of image and point cloud is deeply carried out.Based on the characteristics of ToF image,an image and point cloud fusion feature construction method is designed to fuse ToF image information effectively.Based on this fusion feature construction method,the ORBFPFH(Oriented FAST and Rotated BRIEF and Fast Point Feature Histograms)fusion feature with outstanding matching performance is obtained,enhances the robustness of the feature.At the same time,an ORBFPFH fusion feature-based reconstruction method of space non-cooperative target point cloud is proposed,realizes the high-precision reconstruction of space non-cooperative target point cloud.Aiming at the problem that the point cloud-based target pose measurement method is sensitive to the noise of point cloud and requires high initial pose accuracy,the research on the space non-cooperative target pose estimation method based on retina-like sampling feature and iterative closest point is deeply carried out.A method of constructing binary point cloud features based on retina-like sampling is proposed.Two kinds of point cloud features based on retina-like sampling are constructed based on the two kinds of retina sampling patterns designed.At the same time,a two-stage target pose estimation method is proposed,which is divided into the coarse estimation of the target pose based on the retina-like sampling feature and the precise estimation of the target pose based on the iterative closest point algorithm.The high-precision target pose measurement is realized.Finally,to verify the proposed method’s correctness,the research on the experimental verification method of the near-range pose measurement technology of space non-cooperative targets is deeply carried out.The verification experiments of space targets ToF imaging simulation method,point cloud reconstruction method,and pose estimation method are carried out by building ground exp eriment scenes.The experimental results show that the mean error,variance error,mean square error,and structural similarity of the space target ToF imaging simulation method are better than the traditional simulation methods,the mean error of the gray scale is less than 2.59%,verifies the correctness of the physics-based space target ToF imaging simulation method;When the ToF camera is 1.56 m away from the center of the target body,the average distance error of the reconstructed point cloud is5.95 mm,the chamfer distance error is 20.89 mm,the length error of the solar arrays feature in the reconstructed point cloud is 2.26 mm,the width error is 3.03 mm,and the relative error is less than 0.87%.The point cloud reconstruction accuracy is high,verifies the correctness of the space non-cooperative target point cloud reconstruction method based on the image and point cloud fusion feature;The translation and rotation error of pose estimation are less than 15.76 mm and 1.46°respectively,verifies the correctness of the pose estimation method of space non-cooperative targets based on retina-like sampling feature and iterative closest point.