Autonomous Orbit Control of a LEO Spacecraft

12/05/2023

The increasing number of satellites orbiting Earth, alongside recent advances in electric propulsion technologies and in on-board computational capability, call for novel autonomous orbit control solutions. In this thesis, the orbit control problem is formulated as a formation keeping problem, where the reference spacecraft fulfills the mission requirements. Taking advantage of the periodic characteristics of a satellite's orbit, a discrete-time linear periodic model of the relevant dynamics is developed. The proposed model is shown to have comparable accuracy to nonlinear models of the same dynamics found in the literature. A novel solution for the discrete-time periodic Riccati equation (DPRE) is proposed, and then leveraged in the design of a linear-quadratic regulator (LQR) for autonomous orbit control. The proposed algorithm for the solution of the DPRE is computationally efficient and can be applied to singular systems, contrary to some alternative algorithms. The control system proposed in this thesis achieves accurate reference tracking of all Keplerian elements, with low fuel consumption, resorting solely to transverse and normal actuation. Notably, the control algorithm leverages the dominant orbital mechanics of the problem, prioritizing station-keeping maneuvers at the optimal locations along the orbit, while remaining computationally light. Resorting to high-fidelity simulations, it is shown that the proposed control algorithm attains more accurate reference tracking, with lower fuel consumption, than an autonomous orbit control system designed for the PRISMA mission: one of the most precise orbit control systems found in the literature. Lastly, the control system is also validated for the correction of orbit injection errors.

Authors in the community:

• 

  B

  Bruno Filipe Antunes Midões

  ist192668

Supervisors of this institution:

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  P

  Pedro Tiago Martins Batista

  ist14388

mechanical-engineering - Mechanical engineering

por - Portuguese

Instituto Superior Técnico