Dynamic Sliding-mode Control with Backstepping for Offshore Boarding Gangway

This paper focuses on the control challenge of the movable ladder section of an offshore boarding ladder. A dynamic sliding mode control (DSMC) method based on the backstepping approach is proposed. To address the disturbance mismatch problem in traditional control strategies, the backstepping approach is adopted for the hierarchical design of the control law, decomposing the complex nonlinear system into low-order subsystems for step-by-step processing. Meanwhile, by integrating the strong anti-disturbance advantage of DSMC, a composite control framework with disturbance compensation capability is constructed, which effectively suppresses the nonlinear disturbances caused by external disturbances and system parameter perturbations during the movement of the movable ladder section. The stability of the proposed control method is strictly proven using the Lyapunov function. Simulation results show that the speed response adjustment time of the movable ladder section is less than 10.3 ms, and the position tracking error is controlled within 1.03 mm. Compared with the traditional PID control, the rise time of DSMC is improved by 89.16%, and the tracking accuracy is improved by 90.98%. Facts fully prove that the effectiveness of the proposed method is solidly established.