Modelisation et controle non lineaire pour le suivi de chemin d'un robot mobile sur terrains a adherence limitee

This project examines the classical problem of the path tracking of a mobile robot in the specific context of limited adherence soils. In order to study the displacement of the mobile robot on a ground with limited adherence, we model both the dynamics of the robot and of the ground. Two models are developed: the first model assumes a ground with an ideal adherence whereas the second model takes into account a soil model that uses the slip of the wheels (phenomenon that appears when the ground is not perfectly adherent) and the side slip. We investigate the behavior of the mobile robot for both models and we illustrate the usage of a typical path-tracking algorithm on the first model on an ideal ground. We then show in what ways the path-tracking algorithm is disturbed when the mobile robot moves on a ground where the slips are no more negligible; on a ground which has a limited adherence. We observe that the path-tracking algorithm cannot follow correctly its path when the assumptions of non slipping do not hold. We show that it is possible to use the soil model to develop a new dynamic controller, part of the path-tracking controller, which will allow the overall path-tracking controller to remain effective even when the robot slips on a ground with limited adherence. Finally, we use simulations to illustrate that the proposed dynamic controller functions adequately on several types of natural grounds and on snowy or frozen grounds. All parts of this work are validated by simulations using the computer tools Matlab and Simulink.