Energy-efficient exact-time chattering-free recursive sliding mode control of UUVs based on disturbance observer

Area of Science:

• Robotics and Control Systems
• Marine Engineering
• Autonomous Systems

Background:

• Unmanned Underwater Vehicles (UUVs) require precise trajectory tracking for marine tasks.
• Predefined-time control methods often lead to overestimation of settling time and excessive initial control effort.
• Actuator saturation is a concern with existing control strategies for UUVs.

Purpose of the Study:

• To develop an energy-efficient trajectory tracking control strategy for UUVs with exact-time convergence.
• To address the limitations of predefined-time control, specifically overestimation and excessive initial control effort.
• To improve UUV performance under external disturbances.

Main Methods:

• An exact-time recursive sliding mode control (ETRSMC) scheme using trigonometric-type functions was developed.
• An exact-time disturbance observer (ETDO) was designed for accurate, time-independent disturbance estimation.
• The ETDO was integrated with the ETRSMC to attenuate disturbances and maintain low control gain.

Main Results:

• The proposed ETDO-ETRSMC scheme ensures exact-time convergence at user-defined settling times.
• Peak control effort was reduced by 88.2%-98.7% compared to predefined-time methods.
• Average energy consumption decreased by 35.8%-96.9% while maintaining accuracy and suppressing chattering.

Conclusions:

• The ETDO-ETRSMC strategy offers superior energy efficiency and reduced control effort for UUV trajectory tracking.
• Exact-time convergence is achieved, overcoming limitations of predefined-time control.
• The method effectively handles disturbances and minimizes actuator saturation risks.