Safe Sliding Mode Control for Marine Vessels Using High-Order Control Barrier Functions and Fast Projection

TL;DR

This work tackles safe, robust navigation of a 3-DOF marine vessel under wind, waves, and current disturbances. It develops a safe sliding-mode control framework by embedding a high-order control barrier function for obstacle avoidance and a lightweight projection-based safety filter to replace costly online optimization. The approach preserves the robustness of SMC while guaranteeing forward invariance of a safe set and enabling real-time operation on resource-constrained platforms, as demonstrated against a tube-based NMPC benchmark. The results indicate strong obstacle avoidance, practical stability of the sliding surface, and substantial computational savings, suggesting high relevance for small marine robots and surface vessels with limited onboard processing.

Abstract

This paper presents a novel safe control framework that integrates Sliding Mode Control (SMC), High-Order Control Barrier Functions (HOCBFs) with state-dependent adaptiveness and a lightweight projection for collision-free navigation of an over-actuated 3-DOF marine surface vessel subjected to strong environmental disturbances (wind, waves, and current). SMC provides robustness to matched disturbances common in marine operations, while HOCBFs enforce forward invariance of obstacle-avoidance constraints. A fast half-space projection method adjusts the SMC control only when needed, preserving robustness and minimizing chattering. The approach is evaluated on a nonlinear marine platform model that includes added mass, hydrodynamic damping, and full thruster allocation. Simulation results show robust navigation, guaranteed obstacle avoidance, and computational efficiency suitable for real-time embedded use. For small marine robots and surface vessels with limited onboard computational resources-where execution speed and computational efficiency are critical-the SMC-HOCBF framework constitutes a strong candidate for safety-critical control.

Figures (5)

• Figure 1: Environmental disturbances used in simulations.
• Figure 2: Obstacle-avoidance trajectory using the proposed SMC--HOCBF controller.
• Figure 3: Sliding surface components.
• Figure 4: SMC Boundary Layer.
• Figure 5: Obstacle-avoidance trajectory using the tube-based NMPC with CBF. The trajectory exhibits more conservative deviation, reflecting the Monte Carlo-derived tube inflation.