Adaptive Sliding Mode Control for Robust Trajectory Tracking of Car-Like Mobile Robots in Autonomous Navigation Systems

This study proposes an Adaptive Nonsingular Fast Terminal Sliding Mode Control (Adaptive-NFTSMC) control method for four-wheeled Car-Like Mobile Robots (CLMRs) to enhance trajectory-tracking performance. The controller extends the Nonsingular Fast Terminal Sliding Mode Control (NFTSMC) technique with Lyapunov-based adaptive laws that update control parameters and estimate the upper bound of disturbances. As a result, the system is able to effectively cope with uncertainties and disturbances without pre-assumptions on amplitude limits, overcoming the limitations commonly found in traditional NFTSMC. The approach features a simple structure, rapid response, absence of chattering, high tracking accuracy, robust stability, singularity avoidance, and finite‑time convergence. Moreover, Adaptive‑NFTSMC is designed for straightforward integration into standard autonomous navigation stacks, enhancing its practical applicability. Closed‑loop stability is rigorously proven through Lyapunov analysis and verified via MATLAB/Simulink simulations. Simulation results show that Adaptive‑NFTSMC outperforms classical SMC and an existing Adaptive NFTSMC (ANFTSMC), particularly under conditions with uncertainties and disturbances.