Doctoral defence: Ikechukwu Chinonso Ofodile „Fault Tolerant Attitude Control For Nanosatellites:ESTCube-2 Case“

On February 12 at 10:15 a.m., Ikechukwu Chinonso Ofodile defend his doctoral thesis „Fault Tolerant Attitude Control For Nanosatellites: ESTCube-2 Case“

Superivisors:
Professor Gholamreza Anbarjafari, University of Tartu
Associate Professor Andris Slavinskis, University of Tartu

Opponent:
Associate Professor Jaan Praks, Aalto University, Finland

Summary: This research was carried out at the University of Tartu, Tartu Observatory, the Finnish Meteorological Institute and the Estonian Student Satellite Programme. This thesis presents the ESTCube-2 attitude determination and control system (ADCS). ESTCube-2 is a satellite built according to the three-unit CubeSat standard. The main scientific mission of ESTCube-2 is to perform the in-orbit electric solar wind sail demonstration. The electric solar wind sail is a propellant-less propulsion technology concept. Ultimately, the ESTCube-2 nanosatellite will aim to demonstrate technologies for deep interplanetary space mission of CubeSats and nanosatellites.
This thesis focuses on designing a fault-tolerant control architecture for the ESTCube-2 nanosatellite, which is tasked with demonstrating plasma brake technology in Low Earth Orbit (LEO). The satellite has specific requirements for its ADCS to achieve its mission objectives, including tether deployment and angular momentum control with pointing accuracy and pointing stability of 0.25 deg and 0.125 deg /s respectively. The research aims to provide a fault-tolerant control (FTC) architecture that can handle faults and disturbances without the need to identify the faults, thus reducing computational complexity. An integrated anti-windup fault-tolerant control architecture is proposed. This includes the design of an anti-windup (AW) compensator, which addresses actuator saturation. Two design approaches are discussed: a full-order multi-input multi-output (MIMO) AW compensator and single-input/single-output (SISO) or single-input/multi-output (SIMO) designs. The SISO/SIMO approach is considered for each individual control channel, providing transparency and flexibility for independent channel design and tuning.
The AW compensator’s performance is found to be promising, reducing computational burden and simplifying channel tuning. The thesis also proposes a combination of this architecture with an Adaptive Neuro-Fuzzy Inference System (ANFIS) controller, which offers smoother control reactions in the presence of faults.