Backstepping-based Robust Control for WMR with A Boundary in Prior for the Uncertain Rolling Resistance

In this study, we focus on the trajectory tracking control problem of a wheeled mobile robot (WMR) in an uncertain dynamic environment. Concerning the fact that the upper boundary may be usually achieved in prior according to the physical properties of the terrain, this crucial message is utilized to construct the controllers. Firstly, a dynamic model for WMR including the rolling resistance is presented, whose state variables are longitudinal and rotational velocities, as well as the rotational angle of the mobile platform. Secondly, with the aid of backstepping technique, the robust controllers based on the upper boundary are proposed and the globally asymptotic stability of the closed-loop system is proven by the Lyapunov theory in the following. Lastly, a saturation function is applied to replace the signum function, by which the inherent chattering can be suppressed greatly. Numerical simulation results demonstrate that the proposed controllers with upper bound in prior possess robustness characteristics which yields potentially valuable applications for the mobile robot, especially in the unstructured environment.