Abstract:

 A multiple RGB-D cameras based computer vision astronaut motion capture system, SpaceMocap, is proposed. In the ground preparation phase, the astronaut model is scanned and the internal parameters of the color camera are calibrated separately. In the on-orbit acquisition phase, 3 to 4 cameras are placed in cabin corners to simultaneously capture the astronaut mission video. In the ground processing phase, the cloud point fusion is achieved by calibrating the external parameters of the cameras and the ICP method. The joints position of the human body is detected by a deep neural network and the human pose is initialized. The improved ICP method is used for pose refinement, and the joint angle tracking is achieved in sequence images. The system was launched with TG-2, and collected and processed the mission video of the SZ-11 astronauts. For the first time, it acquired the important data of the on-orbit astronauts' posture (including the neutral body posture), occupation space, and motion parameters. The experimental results show that the model of motion capture has good coincidence with the point clouds; the joint position and joint angle have high tracking accuracy. SpaceMocap is the first on-orbit motion capture system in China. It is small and lightweight, and has the unique advantages of non-contact measurement, intuitive, and high-precision in computer vision. It does not need to stick any markers on the human body and has good anti-occlusion performance. It is totally suitable for on-orbit applications in microgravity and small space environments.

Key words:  Human posture, Motion capture, Computer vision, Astronaut, On-orbit