Study On Augmented Reality Simulation Scene Construction Technology For Tele-Operation Of Space Robot In Cabin

Now, space robotics and its tele-operation technology have become the most important research areas in many countries with advanced aerospace technology, and make great sense in enhancing country's competition ability and security in space area. Because of the particularity and significance of its application areas, tele-operation of space robot has severe demand on the speed and accuracy of information's feedback. The delay and error of information feedback can misguide operator's judgment, and probably lead to control failure and great economy loss. Aiming at the time delay problem in space robot's tele-operation, this research advanced a parallel and distributed augmented reality(AR) simulation scene construction system to construct augmented simulation scene for tele-operation of space robot in cabin real time and reliably. This scene construction system realized complete alignment and reliable fusion of virtual robot model and real scene of space cabin by constructing high performance architecture, using fast and precise calibration and registration method and designing multi-layer occlusion detecting algorithm. And at the same time, image mosaic technology and large field-of-view 3D display system are used too to realize large field-of-view and high immersion display of the fusion scene. Thus, real time, precise and immersive simulation information can be obtained for tele-operation of space robot in cabin. Main research contents include:Firstly, a parallel and distributed architecture of AR simulation scene construction is advanced base on that the robot tele-operation environment in space cabin is fixed and measurable. The related synchronization control mechanism and network communication techniques are researched. This kind of architecture can provide high performance process platform for reliable and immersive AR simulation scene construction.Secondly, full experiments and detailed analysis are made on registration error of AR for Direct Line Transformation(DLT) calibration algorithm and Tsai two steps calibration algorithm respectively, and a fast and accurate camera calibration method is put forward based on the experiment results. This calibration method realizes fast calibration and registration by using DLT algorithm which don't need to do aberration correction, and realizes accurate registration by making the measurement volume occupy whole camera's effective registration space.Thirdly, to resolve the problem that there isn't any uniform evaluation standard of AR's 3D registration technique and it's difficult to make quantitative evaluation to compare the performance of different registration algorithms, a set of evaluation factors relative virtual-real registration are concluded and identified. These factors include stationary registration accuracy, registration space size, computation cost, algorithm's robustness, hardware cost, preparation labor and system applicability etc. all these factors can be classified into to categories: one is concerning the registration quality, and the other is concerning the system's requirements.Fourthly, a fast and accuracy multi-layer occlusion detecting algorithm is put forward to realize real time and robust multi-layer occlusion detection between virtual and real projections in augmented reality system. The basic occlusion detecting algorithm based on geometry stereo matching has low computation cost by avoiding deepness calculation. Based on display status' spatio-temporal continuity, status combining algorithm is advanced to resolve occlusion detecting of points whose feature matching is unsuccessful. The effective edge points detecting algorithm is designed to increase the accuracy of status combining algorithm by using higher reliable edge points to do status combination. And finally, unitary continuity optimization is done on all points to improve the display quality of fusion image.Fifthly, large field-of-view AR simulation scene is obtained by image mosaic in Image-based Rendering technology. Aiming at the problem that current image alignment methods for normal images can not achieve speed and accuracy requirements for real-time and seamless mosaic among multiple video streams, an image mosaic solution based on camera calibration and phase correlation is put forward. Camera's calibration information and FFT's translation feature are used together to realize fast and seamless image mosaic among multiple video streams whose effective depth scale of scene is relatively small. This solution's good accuracy comes from the precise calibration parameters, and the fast speed is obtained by avoiding repetitious FFT and IFFT computation.Finally, a simple experiment prototype of AR scene construction system for tele-operation of space robot in cabin is realized. The experiment results proved the correctness and validity of the system design.