Attitude Control of a 2U Cubesat by Magnetic and Air Drag Torques

TL;DR

This paper presents a magnetic attitude control system for a 2U cubesat, leveraging air drag panels and advanced control strategies to achieve stable pointing despite disturbance torques.

Contribution

It develops controllability conditions for a magnetically controlled cubesat with passive air drag panels and demonstrates effective control using LQR and MPC in simulations.

Findings

System is controllable under certain conditions

Control strategies successfully reject disturbances

Simulation results meet mission objectives

Abstract

This paper describes the development of a magnetic attitude control subsystem for a 2U cubesat. Due to the presence of gravity gradient torques, the satellite dynamics are open-loop unstable near the desired pointing configuration. Nevertheless the linearized time-varying system is completely controllable, under easily verifiable conditions, and the system's disturbance rejection capabilities can be enhanced by adding air drag panels exemplifying a beneficial interplay between hardware design and control. In the paper, conditions for the complete controllability for the case of a magnetically controlled satellite with passive air drag panels are developed, and simulation case studies with the LQR and MPC control designs applied in combination with a nonlinear time-varying input transformation are presented to demonstrate the ability of the closed-loop system to satisfy mission objectives despite disturbance torques.