Double-loop tracking control for a wheeled mobile robot with unmodeled dynamics along right angle roads.

In this study, a double-loop tracking control strategy is investigated to realize trajectory tracking control for a wheeled mobile robot (WMR) with unmodeled dynamics. More specifically, two nonlinear ESOs are designed to estimate disturbances from external disturbances and unmodeled dynamics. Combining with integral sliding mode control and backstepping control, a double-loop tracking controller is designed to enhance tracking accuracy for the WMR along the right angle roads. Based on Lyapunov methods, convergence analysis is given for both the nonlinear ESOs and the double-loop tracking controller. Validity of the double-loop tracking control strategy is demonstrated by experimental results on the WMR along a right angle road. • A double-loop tracking controller is proposed to improve tracking precision on trajectory tracking of the right angle roads for the WMR. • Sufficient conditions of adjustable parameters are given for nonlinear ESOs to estimate internal disturbances from unmodeled dynamics. • A sliding control law with nonlinear functions instead of sign functions is designed to weaken the chattering of sliding mode control system. [ABSTRACT FROM AUTHOR]