GNC Design and Orbital Performance Evaluation of ISS Onboard Autonomous Free-Flying Robot Int-Ball2

The International Space Station (ISS) crew has to complete various tasks in a limited time. The Int-Ball project is one of the activities aimed at the efficient utilization of crew time. Int-Ball2 is an autonomous mobile robot that conducts imaging operations in place of crew members by remote control from the ground. This paper first introduces the design of the guidance, navigation and control (GNC) and propulsion systems of Int-Ball2, offering autonomous flight inside the ISS. This robot has unique features compared to other free-flying robots in space, including its small size for use in crowded environments and its high thrust despite its size. In addition, the navigation system uses a visual SLAM algorithm, which does not rely on external markers. The results of orbital performance verification tests for 6-DOF translational and rotational motion are also presented in this paper. Our analysis indicated that the proposed GNC algorithm provided sufficient performance to conduct the required photography. Finally, the results of ground tests simulating the microgravity environment are compared with the results of orbital experiments to evaluate the differences in the robot’s mobility performance in these tests. The results confirmed that the ground verification method was valid for achieving stable on-orbit mobility.