Relative Position Control for Satellite Formation Flying

Satellite formation flying is a field where the relative positions between two or more satellites are tightly controlled. It is a relevant and growing field that enables missions that otherwise might not be achievable using a single monolithic satellite. This thesis focuses on designing and evaluating different relative positional controllers for satellite formation flying. The objective is to establish a methodology that facilitates effective relative control across a broad range of formation flying missions without dictating actuator models specific to a given mission or committing to a specific spacecraft configuration. The work provides a fundamental description of satellite dynamics and reference frames to provide insight into the nature of the formation flying problem. A custom simulator is developed using a modified equinoctial element based propagator to allow for advanced visualisation and controller evaluation. Two Model Predictive Controllers (MPCs) were designed to showcase how effective this control architecture is under different state representations. The relative satellite states were defined using the Earth-Centred Inertial (ECI) and the Relative Orbital Element (ROE) representations. The ECI-based controller offered intuitive insight into the controller’s decisions, but did not perform well under practical control intervals. The ROE-based controller performed well under practical control intervals and under various along-track separations, but required proper hyperparameter tuning. A novel hyperparameter tuning strategy was developed using Bayesian optimisation to improve controller performance. Seven hyperparameters were tuned using a unique algorithm that penalised satellite crashes and rewarded lowrelative positional error between the satellites. The algorithm was integrated directly into the custom simulator to extract satellite positions over time and score them immediately. Hyperparameter importance analysis showed that some hyperparameters were highly dependent on the initial orbital conditions, whilst others were more independent. Overall evaluation of the ROE-based MPC showed that it was able to control the relative positions between two satellites effectively. Further investigation into the dependence of some hyperparameters on initial conditions is recommended.

Grantor dc:publisher

Stellenbosch : Stellenbosch University

Year dc:date.issued

2026

Author dc:creator

• Moen, Regan

Advisor dc:contributor.advisor

• Jordaan, Hendrik W.

Language dc:language.iso

en

Repository record dc:identifier.uri

https://scholar.sun.ac.za/handle/10019.1/136191

OAI identifier oai:identifier

oai:scholar.sun.ac.za:10019.1/136191