First Advisor

Joshua Méndez

Term of Graduation

Summer 2026

Date of Publication

8-18-2026

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Electrical and Computer Engineering

Department

Electrical and Computer Engineering

Language

English

Subjects

ADCS, Attitude Control, Attitude Determination, Attitude Determination and Control, CubeSat, Reaction Wheel

Physical Description

1 online resource (xiii, 185 pages)

Abstract

Reaction wheels provide the primary means of precision attitude control for many CubeSat attitude determination and control systems by exchanging angular momentum with the spacecraft body. As the Portland State Aerospace Society's OreSat spacecraft transitioned from a 2U to a 3U configuration, the increased spacecraft inertia reduced the attitude control authority available from the legacy reaction wheel system. This thesis addresses that challenge through the redesign of the reaction wheel system and the development of a deterministic embedded controller and experimental framework for evaluating brushless motor commutation strategies under identical operating conditions.

The redesigned system combines an analytically sized flywheel, a custom three-phase motor controller, and a modular firmware architecture implemented using the Zephyr Real-Time Operating System. Hardware-synchronized sensing, fixed-rate control execution, and asynchronous telemetry establish a repeatable hardware-in-the-loop methodology in which trapezoidal, sinusoidal, and field-oriented control are evaluated using common hardware, sensing, timing, and data acquisition, establishing a repeatable framework for evaluating reaction wheel controllers. Performance is characterized through measurements of electrical power and energy consumption, phase current, steady-state speed regulation, torque-producing capability, dynamic response, and thermal behavior.

The experimental results demonstrate that no single commutation strategy provides superior performance across every evaluated metric. Trapezoidal commutation exhibits the lowest cumulative electrical energy consumption and the best thermal performance, while field-oriented control provides the strongest dynamic response, highest measured reaction torque, and most consistent steady-state torque behavior. Sinusoidal commutation generally provides intermediate performance without demonstrating a distinct overall advantage. Collectively, these results support the selection of field-oriented control for the OreSat attitude determination and control system.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/45121

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