Free-Floating Robot Inertial Parameter Identification Towards in Orbit Servicing

Abstract

This master thesis work focuses on the inertial parameter identification of a space robot by exploiting an object of known inertial properties placed at the end-effector of the robotic arm and angular momentum conservation. On-orbit servicing tasks are becoming every day more crucial due to the exponential growth experienced by the space sector in the recent years. The accurate knowledge of the inertial parameters of a servicing platform is fundamental to accomplish complex missions which require high precision. In this context the method developed in this research work, which was carried out at the DLR's Institute of Robotics and Mechatronics in Oberpfaffenhofen (Germany), will extend the already well-covered topic of space manipulators in-orbit identification with algorithms tailored for platforms that do not have reaction wheels on board (e.g. ISS Astrobees). Besides validating the method with offline simulations, tests were performed for a freefloating robot with a 7 degrees of freedom arm on DLR's OOS-SIM experimental facility, providing an onground validation in a close to representative environment. The identification results show that the full dynamic model of the free-floating robot can be identified with the known load at its end-effector, giving comparable results to those in the literature, ready to be used in a model-based control framework.