A Fixed-Time Adaptive Barrier-Based Integral Super-Twisting Sliding Mode Control for Uncertain Wheeled Mobile Robots

Abstract

This paper proposes a novel fixed-time adaptive barrier-based integral super-twisting sliding mode control strategy for uncertain wheeled mobile robots subject to wheel slip, skidding, and external disturbances. Unlike existing prescribed-performance sliding mode approaches, the proposed controller integrates a barrier Lyapunov function with an adaptive integral super-twisting mechanism to ensure strict state constraint satisfaction while eliminating the need for predefined performance bounds. The controller guarantees that tracking errors evolve within dynamically shrinking safe sets and converge to zero within a fixed time independent of initial conditions. A new nonlinear sliding manifold is developed by combining barrier transformation and fractional integral dynamics, which improves transient performance and robustness. An adaptive disturbance compensation law is incorporated to estimate unknown uncertainties without requiring prior knowledge of their bounds. Rigorous stability analysis is conducted using Lyapunov theory, and new sufficient conditions are derived to guarantee fixed-time convergence and boundedness of all signals. Theoretical results demonstrate that the proposed control scheme achieves faster convergence, reduced chattering, and improved robustness compared to conventional sliding mode, non-singular fast terminal sliding mode, and fixed-time prescribed performance controllers. Simulation studies involving straight-line and U-shaped trajectory tracking validate the effectiveness and superiority of the proposed method under severe disturbances and wheel slip conditions.