Magnetic Docking Mechanism for Free-flying Space Robots with Spherical Surfaces

The autonomous operation of robots in the International Space Station (ISS) is required to maximize the use of limited resources and enable astronauts to concentrate more on valuable tasks. To achieve these goals, we are developing a station where the robot approaches, docks, charges, and then undocks. In this paper, the authors propose a magnetic docking mechanism for free-flying robots with spherical surfaces that makes it possible for a robot to dock securely without requiring highly precise guidance, navigation and control capability. By making use of a slider guide and repelling pairs of magnets, this mechanism can achieve tolerance for larger robot position error as compared with the conventional fixed guide mechanism. The experimental results show that the proposed mechanism can effectively enlarge the acceptable error range of poses, and also reduce acceleration at the moment of impact. We also introduce a model to predict the success or failure of docking from the contact condition of the robot and the guide by using a machine learning technique - Gaussian Process Regression (GPR). The prediction results shows that the learnt model can express the contact condition of successful docking.