Robust nonlinear feedback control for Rendezvous in near-circular orbits

• Main Author: Godinho, Eduardo David
• Publication Date: 2019
• Format: Master thesis
• Language: eng
• Source: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Download full: http://hdl.handle.net/10400.6/8942
• topic: Lyapunov; Não-Coplanares; Rendezvous Espacial; Robustez; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

The growing development of the space sector has been driving new technologies and innovative methods. One of these methods, the orbital rendezvous, has been around since the 1960s and consists of bringing together two spacecrafts, one of them is passive, named "target", and the other is active, called the "chaser". This second spacecraft, in turn, performs maneuvers with the aid of thrusters in order to reduce the relative distance between the two vehicles until it is approximately zero. Initially, this process was done manually, however, today technology has progressed such that the process can be completely autonomous. At the beginning of the automation of this space maneuver, the concern would only be to complete the mission, however, it has progressed towards improving this automation process taking into account propellant consumption and the amount of time spent to perform it. Thus, the present dissertation aims to develop and implement a robust controller, based on a Lyapunov’s approach, to show its performance, robustness, and effectiveness in an orbital rendezvous mission. By using a linear dynamic system, where the orbital eccentricity of the target is assumed to be a system uncertainty, the nonlinear controller can create a smooth trajectory so that the chaser approaches the target. The results show that this nonlinear controller can find the solution to the problem of rendezvous for short relative distances and low relative speeds as well as for large, always generating smooth paths without overshooting the target. It was also found that even by disturbing the system with uncertainty, the controller can generate a robust trajectory with great results. This type of controller for rendezvous missions, besides being robust and effective, as demonstrated in the obtained results, can generate excellent results for rendezvous between non-circular non-coplanar orbits.