Date of Award

8-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Aerospace, Physics, and Space Sciences

First Advisor

Madhur Tiwari

Second Advisor

Seong Hyeon Hong

Third Advisor

Eric Swenson

Fourth Advisor

David Fleming

Abstract

The growing demand for on-orbit servicing and assembly as well as orbital debris capture and removal poses many engineering challenges. One primary challenge is that of position and attitude control of a spacecraft-manipulator system while performing these operations. Standard control approaches may be used for cases where the dynamics of the objects that the spacecraft-manipulator system interacts with are known are still plausible. However, there will likely be some uncertainty and lack of knowledge of the dynamic properties of orbital debris and parts required for servicing. Therefore, many have proposed the use of adaptive control schemes which can recalculate the gains of the controller in real time to adjust to the coupled spacecraft and capture object dynamics. This thesis focuses on the comparison of an adaptive variable structure controller and a standard PID controller as applied to a 3-DOF air-bearing vehicle and 2-DOF manipulator system. The non-linear, time-varying dynamic model utilized in Simulink to achieve a high-fidelity simulation. This research shows that for a mass increase of the end-effector link of 19% of the total system mass, which amounts to 2.39 kg, and an increase of 19% in the moment of inertia of the end-effector link, the PID controller was unable to control the system while the adaptive controller successfully controlled the system within design requirements.

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