Attitude Dynamics and Control of Satellites With Fluid Ring Actuators
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Notice bibliographique
Résumé
Successful mission of a satellite depends on maintaining a fixed orientation with respect to the Earth. However, the attitude angles of a satellite can be perturbed because of various natural disturbance sources, such as the Earth's gravity gradient, solar radiation pressure, and the Earth's magnetic field. Modeling the attitude dynamics and developing a controller to stabilize the attitude motion are quite important steps in the design of satellites. Although several actuators exist to control the attitude motion, a novel type considered in the thesis, shows promise of producing a high torque to mass ratio. This potential justifies the in-depth study reported. The novel actuator in question consists of a ring containing fluid, whose flow is regulated by a pump. The control torque is produced due to the variation of the angular velocity of the fluid. In this thesis, first, a redundant actuator system composed of four fluid rings in a pyramidal configuration is studied. The dynamical model of the system is developed for a satellite travelling either in a circular or an elliptical orbit. The dynamical analysis of this system leads to an underdetermined system of nonlinear differential equations, whose solution without considering the control input (the torque produced by the pump pressure) shows that the fluid rings can damp out the attitude disturbances of a satellite in a circular orbit and the roll-yaw disturbances in an elliptical orbit. However, this passive damping effect is fairly slow; an active controller is hence designed in the next step. The effect of the failure of one fluid ring on the performance of the attitude control subsystem (ACS) of a satellite is also studied. It is observed that even in the case of failure of one fluid ring, the satellite can be stabilized by slight modification of the active controller. Later, a sliding mode controller is designed to cope with the uncertainties existing in the fluid model and in other parameters of the system. Although the results achieved are quite satisfactory, the chattering that exists in the steady response of the system is not desirable; hence a switching controller consisting of a sliding mode and a PID control law is designed to eliminate this chattering effect. Next, the theoretical results obtained are validated by conducting several experiments. Although the experimental results confirm the theory developed in this thesis, the large torque-to-mass ratio expected is revealed to be only possible at the cost of a quite high input voltage to the pumps regulating the flow. Therefore, two novel applications of fluid rings are proposed: as an actuator for spin stabilized satellites, or as an auxiliary actuator in satellites with magnetic torquers.Using fluid rings in spin stabilized satellites is proposed in the thesis, as an alternative to the commonly used micro-thrusters. Here, two fluid rings are mounted on the satellite while their axes of symmetry are aligned with the roll and yaw axes. To examine the feasibility and performance, a dynamical model of this spinning satellite with two fluid rings is developed. A controller is then designed to stabilize the attitude motion of this satellite.The second novel actuator system developed here consists in using fluid rings as complementary actuators in satellites with two magnetic torquers. The dynamical model is formulated, and a controller is designed to investigate the performance of this system. The simulation of the system without the fluid ring shows that the satellite attitude can be stabilized by using only two magnetic torquers, however, slowly. Upon adding the active fluid ring actuator to the system, the stabilization time is reduced by a factor of 10. The failure of the fluid ring and each magnetic torquer is also studied.
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Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découle