Date of Award

2020-01-01

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Advisor(s)

Angel Flores Abad

Second Advisor

Louis Everett

Abstract

Space maneuvers in the vicinity of small celestial bodies and achieving a soft landing over the surface of small celestial bodies are essential movements to advance the status of exploration, collection of geographical data, measurement of physical properties among other on-orbit tasks. Before a spacecraft reaches hovering position over an asteroid in order to perform orbital tasks, close-proximity operations must be done. Since the movements of the spaceships depend on the acceleration forces provided by the thrusters and external disturbances forces, the correct planning of execution of the close-up trajectories on the celestial body orbit and trajectory to land on the surface of the body is of cumbersome importance to prevent the vehicle from bouncing up and eventually reach escape velocity uncontrolled. In this Dissertation work, a bio-inspired trajectory planning method for both, close-proximity operations around the asteroid and landing on the surface of a Near-Earth Asteroid (NEA) is proposed. The method is based on Tau theory, which has been demonstrated to explain the way that humans and some other animals' approach to different target spots to perform tasks such as perching, landing and grasping. We have selected the NEA Apophis asteroid as our case study due to its accessibility, and small rotational velocity and orbit condition code. A simulation of close range-range and far-range rendezvous planning trajectories are shown to reach a hovering position on Near-Earth Asteroid (NEA). The solution of the Hill-Clohessy-Wiltshire equations is used to find the required state variables at each time instant. Two landing scenarios are studied; one considers the case where the satellite is hovering at a low altitude; the other corresponds to a landing maneuver right after a deorbiting or breaking phase, which may cause residual initial velocity in the vehicle prior to the landing maneuver. The required trajectory affected by disturbances and orbital uncertainties is analyzed in Simulink by means of a PD-PWPF trajectory tracking control. The simulation results show that the introduced

approach can achieve the final state requirements depending on initial conditions in both close-proximity operations and landing. Besides, different kinematic behaviors of the trajectories using Tau Theory can be obtained by modifying the single variable named the Tau constant. The advantages of the method with respect to a commonly used approach are devised and analyzed as well.

Language

en

Provenance

Received from ProQuest

File Size

113 pages

File Format

application/pdf

Rights Holder

Rene Alberto Valenzuela Najera

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