Synthèse d’une solution GNC basée sur des capteurs de flux optique bio-inspirés adaptés à la mesure des basses vitesses pour un atterrissage lunaire autonome en douceur

Abstract : In this PhD thesis, the challenge of autonomous lunar landing was addressed and an innovative method was developed, which provides an alternative to the classical sensor suites based on RADAR, LIDAR and cameras, which tend to be bulky, energyconsuming and expensive.The first part is devoted to the development of a sensor inspired by the fly’s visual sensitivity to optic flow (OF). The OF is an index giving the relative angular velocity of the environment sensed by the retina of a moving insect or robot. In a fixed environment (where there is no external motion), the self-motion of an airborne vehicle generates an OF containing information about its own velocity and attitude and the distance to obstacles. Based on the “Time of Travel” principle we present the results obtained for two versions of 5 LMSs based optic flow sensors.The first one is able to measure accurately the OF in two opposite directions. It was tested in the laboratory and gave satisfying results. The second optic flow sensor operates at low velocities such as those liable to occur during lunar landing was developed.After developing these sensors, their performances were characterized both indoors and outdoors, and lastly, they were tested onboard an 80-kg helicopter flying in an outdoor environment.The Guidance Navigation and Control (GN) system was designed in the second part on the basis of several algorithms, using various tools such as optimal control, nonlinear control design and observation theory. This is a particularly innovative approach, since it makes it possible to perform soft landing on the basis of OF measurements and as less as possible on inertial sensors. The final constraints imposed by our industrial partners were met by mounting several non-gimbaled sensors oriented in different gaze directions on the lander’s structure. Information about the lander’s self-motion presentin the OF measurements is extracted by navigation algorithms, which yield estimates of the ventral OF, expansion OF and pitch angle.It was also established that it is possible to bring the planetary lander gently to the ground by tracking a pre-computed optimal reference trajectory in terms of the lowest possible fuel consumption. Software-in-the-loop simulations were carried out in order to assess the potential of the proposed GNC approach by testing its performances. In these simulations, the sensor firmware was taken into account and virtual images of the lunar surface were used in order to improve the realism of the simulated landings.
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https://hal.archives-ouvertes.fr/tel-01096458
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Submitted on : Wednesday, December 17, 2014 - 3:25:22 PM
Last modification on : Tuesday, March 26, 2019 - 2:28:03 PM
Long-term archiving on: Monday, March 23, 2015 - 3:25:51 PM

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Guillaume Sabiron. Synthèse d’une solution GNC basée sur des capteurs de flux optique bio-inspirés adaptés à la mesure des basses vitesses pour un atterrissage lunaire autonome en douceur. Physique de l'espace [physics.space-ph]. ISAE - Institut Supérieur de l'Aéronautique et de l'Espace, 2014. Français. ⟨tel-01096458⟩

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