Soft and minimum reactions robotic capture of non-cooperative spacecrafts

Cocuzza, Silvio and Li, Mutian and Yan, Xiu; (2016) Soft and minimum reactions robotic capture of non-cooperative spacecrafts. In: 67th International Astronautical Congress (IAC 2016). International Astronautical Federation (IAF), MEX, p. 3748. ISBN 9781510835825

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Abstract

The capture of non-cooperative targets is a key priority for future space robotics missions. Typical operative scenarios are the maintenance and refuelling of malfunctioning satellites or the capture of space debris. In these operative scenarios, one of the key issues to be addressed is the impact force minimization: a null relative velocity of the robot end-effector with respect to the target is required at the time of capture, otherwise either the target or the robotic system could be damaged, the target could be pushed away, or the chaser spacecraft attitude could be destabilized. On the other hand, it is always desirable that the reaction torques transferred by the manipulator to the base spacecraft are minimized, so that a small amount of fuel is used for the attitude recovery, which is required to maintain the communication link with the ground after the robotic manoeuvre, thus increasing the system operating life. In this paper, two novel methods are proposed and compared for capturing a non-cooperative target with a redundant robot and in the meantime transferring a null reaction torque to the base spacecraft. This is a great advantage with respect to the state of the art capture methods, in which the problem of capture and of reactions minimization are handled separately and their integration is not straightforward. In the first method, the robot end-effector follows a parametric trajectory, which parameters are computed in order to have the same direction and speed of the target at the time of capture. On the other hand, in the second method the end-effector trajectory is computed by making the position and velocity error converge to zero inside the inverse kinematics control loop. The proposed methods have been demonstrated and compared by means of dynamic simulations of a 3-degrees-of-freedom planar manipulator. Both of them have shown a good performance and in particular in both cases the manipulator is able to reach the target with the desired end-effector velocity and with a null reaction torque transferred to the base spacecraft.

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