Trajectory tracking of a wheeled mobile robot using Backstepping and Sliding mode approaches

Differential wheeled mobile robot is constructed from two independent active wheels and a spherical passive wheel. This robot as a result of pure rolling and nonslip conditions of wheels is a nonlinear system subjected to nonholonomic constraints. In addition, this system is classified as an underactuated system. Trajectory tracking we have concentrated on is one of the most complicated problems in control of wheeled mobile robots. In the first step a kinematic model in which linear and angular velocity are supposed as system inputs has been presented. Then using a feasible reference trajectory for the first time a novel full state backstepping controller has been designed and unlike previous approaches the stability has been provided fully stated and globally. Next, a sliding mode controller which is based on input-output control theory has been suggested. The proof of stability of this controller has been presented as well. Then a feedback linearization controller as an efficient approach has been proposed with the aim of comparing the performance of the controllers. Finally, integrity and robustness of designed controllers against disturbances have been approved using MATLAB simulation and the obtained results are discussed.