Date of Award

3-14-2014

Document Type

Thesis

Degree Name

Master of Science in Astronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Richard G. Cobb, PhD.

Abstract

The design and testing of AFIT's 6U Attitude Determination and Control Subsystem (ADCS) are explored to establish 3-axis attitude control. The development of AFIT's 6U CubeSat standard bus is an on-going research effort designed to create in-house CubeSat bus components and software. The 6U chassis measures approximately 11 x 24 x 37 cu cm and can have a mass up to 12 kg. The larger bus size (as compared to the more common 3U CubeSat) allows for increased power capabilities and potential to host multiple or larger payloads. Individual ADCS hardware components were either commercially purchased or built in-house and include an IMU, external magnetometer, 4-wheel reaction wheel assembly, and three torque coils. The ADCS software developed as part of this research includes the QUEST attitude determination algorithm, B-dot de-tumbling algorithm, and PD control algorithm with momentum dumping capability. To facilitate ADCS testing, an air bearing assembly was designed and set up in AFIT's existing Helmholtz cage. The air bearing provides a near-frictionless environment with 360 deg rotation about one axis and limited (35 deg) rotations about the other two axes. The Helmholtz cage consists of three orthogonal magnetic coil pairs that can create a uniform + or - 2 Gauss magnetic eld within the cage. This comprehensive ADCS testing environment was used to test a ground-based 6U CubeSat complete with ADCS, CDH, and EPS components. The custom-built torque coils demonstrated torquing abilities on the spacecraft and yield a 0.66 A-sq m magnetic moment. In addition, single-axis attitude control was achieved using the reaction wheel assembly. Recommendations for further developments and testing are included to achieve the desired 3-axis control.

AFIT Designator

AFIT-ENY-14-M-14

DTIC Accession Number

ADA601225

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