There are millions of pieces of space debris in orbit around Earth that pose threats to operating spacecraft. Some of these debris can be attributed to satellite failure, or end-of-life protocols. With a continual increase in commercial satellite launches per year, decommissioned spacecraft act as more debris polluting the space environment. Not only can robotic arms assist with active orbital debris removal to be more sustainable, they also support robotic on-orbit servicing (OOS). Additionally, using a robotic manipulator enables different servicing operations to take place, allowing for life extension capabilities for expired spacecraft. These life extension services allow for a broader application for robotic arms, which includes rendezvous proximity operations and docking. Robotic arms can also be used for assembly and manufacturing cases, establishing a more sustained presence and creating permanent structures in space. When considering any robotic rendezvous maneuvers or servicing, assembly, and manufacturing tasks aboard a spacecraft, it is important for the parent satellite to maintain attitude throughout robot motion, as in a zero gravity setting, any forces created by the robot act as equal and opposite forces applied to the parent spacecraft. The research performed in this thesis aims to create a model to describe changes in attitude throughout planned robot motion, as well as introduce methods for compensating for potential disturbances. Additionally, methods for describing the kinematics of a robot manipulator are presented and the forces and torques experienced by each joint are calculated using Newton-Euler inverse dynamics. Based on a calculated trajectory of the end effector, these torques are propagated to the parent spacecraft to determine the change in angular velocity. The results of this analysis are used to determine the required angular velocity to apply to the parent spacecraft in order to maintain attitude. / Master of Science / There are millions of pieces of space debris in orbit that threaten operating spacecraft. Spacecraft that are no longer working, yet continue to orbit, are considered space debris. As commercial satellite launches increase each year, orbital debris becomes more of a problem. Instead of disregarding broken satellites and adding to the orbital debris problem, robotic arms can be used to help fix and extend the lives of these spacecraft through acts of refueling or docking with an expired satellite to assume control, as well as provide assistance with orbital debris removal. In a broader sense, robotic arms can help two satellites dock together as well as assist in proximity operations. Robotic arms can be used to manufacture parts and build space structures, establishing a more permanent human presence in space. Because these robot servicing tasks can be very precise, it is important for the attached spacecraft to maintain position and orientation. During any servicing, assembly, or manufacturing task, the motion of a robotic arm produces forces that propagate to the parent spacecraft. If the spacecraft were on the ground, these forces would absorb into the ground, not affecting the position or orientation of the spacecraft. In zero gravity, any forces created by the robot arm act as equal and opposite forces applied to the parent spacecraft. These forces can cause shifts in the satellites position and orientation which need to be compensated for. Methods for describing the motion of the robotic arm are presented, and a model for how the parent spacecraft reacts to this motion is created. The results from this analysis are used to determine the appropriate counterforce to apply to the parent spacecraft in order to maintain desired orientation.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119335 |
| Date | 06 June 2024 |
| Creators | Molitor, Rowan Larson |
| Contributors | Aerospace and Ocean Engineering, Black, Jonathan T., Kenyon, Samantha Parry, Komendera, Erik |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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