An Almost Global Trajectory Tracking Controller for Differential-drive Wheeled Mobile Robots

This paper addresses the trajectory tracking problem of differential-drive wheeled mobile robots with nonholonomic constraints. Contrary to other works that use a simplified kinematic model, we consider the configuration space of the mobile robot in the controller design; that is, the robot's motion evolves on the Cartesian space and the unit circle. Exploiting the cascade structure of the robot's kinematics, we propose a novel linear velocity-free trajectory-tracking controller that guarantees exponential convergence to the desired reference trajectory for almost all initial conditions. Almost global exponential stability of the closed-loop equilibrium point is proven using strict Lyapunov functions. We provide experimental results and a comparison study to validate the excellent performance and advantages of the proposed control algorithm.