| The study of Mars is of growing interest among the scientific community. Given the large distance between this planet and the Earth, as well as the hostile environment prevailing there, its exploration takes advantage of using rovers. The rare communication windows, along with the important delays occuring during communications, justify artificial intelligence deployment on these mobile platforms in order to maximize their autonomy. Hence, one of the crucial issues is the ability the rover has to autonomously navigate and thus, to properly detect its environment with the help of advanced vision systems.;The research project discussed in this thesis focuses on this theme and is done in collaboration with the Canadian Space Agency (CSA). The main objective is to design a three-dimensional vision system enabling a mobile robot to navigate autonomously. It relates more particularly to the design, integration and study of CORIAS (COntinuous Range and Intensity Acquisition System), a vision system using lidar (LIght Detection And Ranging). The system uses a LMS111, manufactured by SICK, as its main sensor. The device developed in this research project not only meets the main objective, but it also has the following characteristics : (1) The three-dimensional reproduction of the environment is performed within a 20 meter radius. (2) The maximum data acquisition rate is 27 050 points per second. (3) The time required to complete a full-coverage scan performed with typical operation parameters (0,25° elevation and 0,50° azimuth resolutions) is around 29 seconds. (4) The system is able to transmit the intensity measurements associated with the acquired points. (5) Vertical (elevation) and horizontal (azimuth) resolutions are configurable and fine enough to detect obstacles. (6) The system has a reasonable level of protection against bad weather conditions (dust, rain, snow, etc.).;CORIAS only requires a 24 volts DC power supply and an Ethernet link to be operated. It can be installed easily on a large variety of platforms. The rover's on-board computer is responsible for communicating with the vision system and provides the commands it needs to accomplish. The microcontroller, which is the central part of the system, operates on Linux and acts as a TCP-IP server. It is responsible, among other things, for managing all the commands, pre-processing data and transferring these to the rover's computer. Data processing is then performed on the rover's onboard computer, where algorithms aiming at filtering points and extracting the navigable mesh are involved.;In the summer of 2011, CORIAS was first used on CSA's Mars Emulation Terrain (MET) for validation purposes. During this three-day test campaign, over 112 georeferenced full-coverage scans were successfully acquired. The data produced by this experiment was used to generate MET's digital elevation map and was shared as a scientific database in the International Journal of Robotics Research (IJRR). In the summer of 2012, CORIAS was finally integrated on the Juno rover, a robotic platform for research and development used by CSA. |
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