Adaptive fuzzy tracking control for underactuated surface vessels with unmodeled dynamics and input saturation

Area of Science:

• Robotics and Control Systems
• Marine Engineering
• Applied Mathematics

Background:

• Underactuated Surface Vessels (USVs) present significant control challenges due to their complex dynamics, including off-diagonal inertial matrices and unmodeled dynamics.
• Input saturation and external disturbances further complicate precise tracking control for USVs.
• Existing control strategies often struggle to effectively address these combined uncertainties.

Purpose of the Study:

• To develop an adaptive fuzzy state-feedback control scheme for underactuated surface vessels (USVs).
• To effectively manage uncertainties arising from unmodeled dynamics and input saturation.
• To ensure robust tracking control performance despite an off-diagonal inertial matrix.

Main Methods:

• An improved USV model incorporating dynamic disturbances from unmodeled dynamics was established.
• A backstepping approach was employed, releasing the off-diagonal inertial matrix by restructuring the kinematic loop.
• Adaptive fuzzy logic systems (FLSs) with minimum learning parameters (MLPs) addressed uncertainties, while K∞ and Gauss error functions compensated for disturbances and input saturation.

Main Results:

• The proposed adaptive fuzzy control scheme demonstrated effective compensation for unmodeled dynamics and input saturation.
• The restructured tracking error allocation successfully addressed the underactuation problem.
• The small-gain theorem confirmed the ultimate boundedness of the closed-loop system, validated by simulation.

Conclusions:

• The developed adaptive fuzzy state-feedback control scheme provides a robust solution for tracking control of USVs with complex dynamics.
• The integration of FLSs, backstepping, and specific compensation functions effectively handles system uncertainties and constraints.
• Simulation results validate the proposed method's effectiveness in achieving stable and accurate trajectory tracking.