An Improved Adaptive Sliding Mode Controller with Dynamic Surface Extension for Uncertain Robotic Manipulators

This article presents an improved adaptive sliding mode control (SMC) scheme designed for uncertain robotic manipulators through a novel dynamic surface extension. Unlike conventional SMC approaches, which have scalar sliding surfaces, our proposed approach introduces a two-stage sliding variable along with a dynamic extension, which allows the independent shaping of reaching and sliding dynamics. The controller adaptively estimates unknown disturbances and ensures finite-time convergence of the sliding variable, while chattering and steady-state errors are suppressed by including the integral term in the dynamic extension. Lyapunov-based analysis was carried out to prove the boundedness of the overall control approach and the asymptotic tracking of the desired trajectory. Simulation studies were carried out on a two-link robot manipulator under varying payloads and external disturbances. The results validate its superior tracking accuracy and disturbance rejection compared to traditional SMC controllers. The results confirm that the proposed control scheme achieves fast convergence, low chattering, and robust performance in the presence of modeling uncertainties, making it a promising solution for high-precision robotic applications.