Hierarchical Decentralized Fuzzy Sliding-Mode Control for the Path-Tracking of Differential Driven Mobile Robots

The goal of this work is to achieve path-tracking of a differential driven mobile robot (DDMR) in the presence of uncertainties, saturated input, and external disturbances. To reach this goal, hierarchical decentralized fuzzy sliding-mode control (HDFSMC), including a nonlinear position control (NPC), is used to generate the desired velocity inputs of the nominal system. A decentralized fuzzy sliding-mode control (DFSMC) is also used to deal with the existence of uncertainties, saturated input and external disturbance in addition to velocity tracking. The error dynamics between the actual DDMR and the virtual reference DDMR (or the desired velocity inputs) with respect to the world frame is first established to asymptotically track the planned trajectory. Usually, the performance and stability of the closed-loop system often deteriorate because of mentioned uncertainties and exogenous inputs. A DFSMC is designed to obtain good performance including accuracy of path tracking and smoothness of the control input by exploiting some of the features of the sliding-mode control technique, e.g., excess robustness, fast convergence. First, a suitable rule table for the ith subsystem is obtained using if-then rules. Then, based on Lyapunov stability criterion, the output scaling factor is then determined. To validate the theoretical developments, computer simulations are conducted which prove the effectiveness, efficiency and robustness of the proposed scheme.