arXiv subjects

Antônio Fernando Bertachini de Almeida Prado

Publications and source records attributed to Antônio Fernando Bertachini de Almeida Prado.

4 recordsLinked to original sources

arXiv2024

Robust Path-following for Keplerian Orbits

This work introduces a novel path-following control strategy inspired by the famous two-body problem, aiming to stabilize any Keplerian orbit. Utilizing insights from the mathematical structure of the two-body problem, we derive a robust path-following law adopting sliding mode control theory to achieve asymptotic convergence to bounded disturbances. The resulting control law is demonstrated to be asymptotically stable. Illustrative examples showcase its applicability, including orbiting an accelerated moving point, patching Keplerian trajectories for complex patterns, and orbital maintenance around the asteroid Itokawa. The proposed control law offers a significant advantage for the orbital station-keeping problem, as its sliding surface is formulated based on variables commonly used to define orbital dynamics. This inherent alignment facilitates easy application to orbital station-keeping scenarios.

eess.SY↗

arXiv2024

Autonomous Rapid Exploration in Close-Proximity of an Asteroid

The increasing number of space missions may overwhelm ground support infrastructure, prompting the need for autonomous deep-space guidance, navigation, and control (GN\&C) systems. These systems offer sustainable and cost-effective solutions, particularly for asteroid missions that deal with uncertain environments. This study proposes a paradigm shift from the proposals currently found in the literature for autonomous asteroid exploration, which inherit the conservative architecture from the ground-in-the-loop approach that relies heavily on reducing uncertainties before close-proximity operations. Instead, it advocates for robust guidance and control to handle uncertainties directly, without extensive navigation campaigns. From a series of conservative assumptions, we demonstrate the feasibility of this autonomous GN\&C for robotic spacecraft by using existing technology. It is shown that a bolder operational approach enables autonomous spacecraft to significantly reduce exploration time by weeks or months. This paradigm shift holds great potential for reducing costs and saving time in autonomous missions of the future.

astro-ph.EP↗

arXiv2024

Shallow Encounters' Impact on Asteroid Deflection Prediction and Implications on Trajectory Design

Analytical approximations are commonly employed in the initial trajectory design phase of a mission to rapidly explore a broad design space. In the context of an asteroid deflection mission, accurately predicting deflection is crucial to determining the spacecraft's trajectory that will produce the desired outcome. However, the dynamics involved are intricate, and simplistic models may not fully capture the system's complexity. This study assesses the precision and limitations of analytical models in predicting deflection, comparing them to more accurate numerical simulations. The findings reveal that encounters with perturbing bodies, even at significant distances (a dozen times the radii of the sphere of influence of the perturbing planet), can markedly disturb the deflected asteroid's trajectory, resulting in notable disparities between analytical and numerical predictions. The underlying reasons for this phenomenon are explained, and provisional general guidelines are provided to assist mission analysts in addressing such occurrences. By comprehending the impact of shallow encounters on deflection, this study equips designers with the knowledge to make informed decisions throughout the trajectory planning process, enhancing the efficiency and effectiveness of asteroid deflection missions.

astro-ph.EP↗

arXiv2023

Study on Autonomous Gravity-assists with a Path-following Control

We investigate the autonomous control of gravity-assist hyperbolic trajectories using a path following control law based on sliding mode control theory. This control strategy ensures robustness to bounded disturbances. Monte Carlo simulations in the environments of Titan and Enceladus, considering significant insertion errors on the order of 50 km, demonstrate the effectiveness of the proposed approach. The Enceladus example showcases the applicability of the control strategy for close flybys of asteroids and small moons during scientific observations. It successfully stabilizes the orbital geometry within a short time span, avoiding collisions and enabling a close approach to Enceladus' surface with a separation distance of 10 km. Furthermore, we explore its application in a Jovian tour, considering a more complex N-body problem. Results indicate that the control system, while unable to guarantee a complete tour, plays a crucial role in ensuring precise trajectory control during flybys. In such cases, the vehicle guidance system requires higher precision than what can be achieved with a patched conics model. These findings demonstrate the effectiveness of the proposed control strategy for gravity-assist maneuvers and highlight its potential for various space exploration missions involving close encounters with celestial bodies.

astro-ph.EP↗