Finite-Time Disturbance Observer-Based Adaptive Course Control for Surface Ships

Area of Science:

• Marine engineering
• Control systems theory
• Robotics

Background:

• Ship course control is challenged by input saturation and external disturbances.
• Existing methods may not adequately address steering engine vibrations or input inconsistencies.

Purpose of the Study:

• To develop a finite-time disturbance observer-based adaptive control strategy for ship course control.
• To mitigate issues arising from input saturation and external disturbances.

Main Methods:

• Designed a smooth saturation model using the Gaussian error function to prevent input saturation and reduce vibrations.
• Introduced an auxiliary dynamic system to compensate for rudder angle inconsistencies.
• Developed a finite-time disturbance observer and an adaptive updating law to estimate external disturbances and their derivatives.
• Proposed a novel adaptive control law using the hyperbolic tangent function.

Main Results:

• The proposed control law demonstrates strong resistance to external disturbances.
• The system exhibits robustness against parameter perturbations.
• Stability analysis confirmed closed-loop system stability and boundedness of signals using LaSalle's Invariance Principle.

Conclusions:

• The novel adaptive control strategy significantly improves ship course control performance.
• The method offers enhanced robustness and stability under challenging operational conditions.