A novel trajectory tracking control approach for nonholonomic wheeled mobile robot based on adaptive recursive integral terminal sliding mode

The trajectory tracking control performance of differential wheeled mobile robots (DWMRs) is subject to nonholonomic constraints, system uncertainties, and external disturbances. Moreover, existing control methods suffer from limitations such as guaranteeing only asymptotic convergence, low tracking accuracy, and the requirement of prior knowledge of system uncertainties for adaptive control design. To overcome these challenges, this paper proposes a novel adaptive trajectory tracking control strategy for DWMRs based on recursive terminal sliding mode control (RTSMC), with a focus on two key aspects: system modeling and the design of an adaptive sliding mode controller. First, a unified kinematic and dynamic model of the DWMR with uncertainties is established, and an error dynamics equation is derived using binary tracking error. Second, based on the established model and RTSMC theory, an adaptive recursive integral terminal sliding mode control (ARITSMC) approach is proposed to achieve high-precision, fast-response and robust tracking performance. The proposed approach offers two primary advantages: (i) The designed recursive integral terminal sliding mode structure eliminates the reaching phase, allowing the closed-loop system to initiate directly on the sliding mode surface, thereby ensuring finite-time zero-convergence of both the sliding mode variables and tracking errors. (ii) An incremental adaptive mechanism, based on the bounded uncertainty assumptions, enables online estimation of the upper bound of the lumped uncertainties, removing the requirement of prior knowledge of uncertainties. Finally, stability analysis and experimental results validate that, compared to existing control methods, the ARITSMC provides superior finite-time zero-convergence and robustness against both system uncertainties and external disturbances.