Design, Modeling, and Validation of a Modular Single-Axis AOCS for a 2U CubeSat

Abstract

This paper details the mathematical modeling, implementation, and validation of a standalone Attitude and Orbit Control System (AOCS) for a 2U CubeSat mission designed for the INPE CubeDesign competition. Addressing the need for low-cost, open-source space technology, this work proposes a modular architecture based on the ESP32 microcontroller that integrates attitude determination and control into a single fault-tolerant unit. The system features a custom reaction wheel assembly driven by an L6234 driver stage, with precise closed-loop control enabled by an AS5600 magnetic encoder. Attitude determination fuses inertial data from an MPU-9250 gyroscope with a “virtual” solar sensor algorithm derived from photovoltaic voltage differentials. The validation methodology followed a rigorous Model-Based Design (MBD) workflow, transitioning from numerical MATLAB/Simulink simulations to Hardware-in-the-Loop (HIL) testing on an air-bearing platform. Experimental results demonstrate a pointing accuracy of 0.5 degrees, validating the effectiveness of the sensor fusion and control strategy.