Author

Asher Smith

Date of Award

12-2017

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aeronautical Engineering

Department

Graduate Studies

Committee Chair

Dr. Dongeun Seo

First Committee Member

Dr. Troy Henderson

Second Committee Member

Dr. Richard Prazenica

Abstract

As spacecraft require higher positional accuracy from the attitude control systems, new algorithm developments, along with sensor and actuator resolution and range improvements are necessary to achieve the desired science accuracies. For agile 6-Degrees of freedom (6-DOF) spacecraft with redundancy, the actuators are usually oversized or overpopulated to meet the desired slew requirements. Currently, most spacecraft utilize an over-actuated thruster system to produce 6-DOF control. This thesis presents a simulation of the OSIRIS-REx mission during the descent phase to the asteroid Bennu, with a focus on utilizing dual quaternion dynamics and a newly developed thruster allocation method. The dual quaternion based dynamics are chosen in order to demonstrate its feasibility in real-time applications. Contrary to typical plant dynamics, which decouple the spacecraft orbit and attitude dynamics, the dual quaternion description provides a compact and coupled dynamics system. Due to the coupled nature of dual quaternions, a newly developed thruster distribution matrix is implemented to take both the coupled command body forces and torques and transform them into the individual thruster frames. The developed method is based on a min-max optimization that results in a constant thruster distribution matrix. From the optimization, a minimum thrust solution is calculated for the coupled position and attitude commands. Therefore, its integration into the dual quaternion dynamics is intuitive and simplistic. The final result is a computationally fast thruster allocation solution for real-time applications.

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