Date of Award

3-24-2016

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Eric D. Swenson, PhD.

Abstract

Dynamic optimization of spacecraft attitude reorientation maneuvers can result in significant savings in attitude determination and control system size, mass, and power. Optimal control theory is generally applied using an open loop trajectory which is vulnerable to disturbances. A closed loop implementation of optimal control has been difficult to achieve due to the computational requirements needed to quickly compute solutions to the optimal control problem. This research focuses on evaluating a near real-time optimal control (RTOC) system for large angle slew maneuvers on the Air Force Institute of Technology's spacecraft simulator called SimSat. A near RTOC algorithm computes optimal control solutions at a rate of 0.4 Hz using a pseudospectral-based solver. The solutions or trajectories are then resampled at a fixed time step of 100 Hz and fed forward to a closed loop on SimSat. This algorithm is developed and tested on the hardware and compared to simulated and hardware results of a proportional-integral-derivative (PID) controller and an open loop optimal control controller for 90 degree and 180 degree Z-axis rotations. The benefits of decreased time to complete the maneuver and increased accuracy at the end of the optimal maneuver are shown to be improvements over traditional over PID control and open loop optimal control.

AFIT Designator

AFIT-ENY-MS-16-M-232

DTIC Accession Number

AD1054190

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