Investigation of Time-varying Limitations in Intelligent Ship Automatic Berthing Control

A backstepping control method combining a time-varying tangent barrier Lyapunov function (BLF) and dynamic surface control (DSC) technology is proposed to address the issue of automatic berthing control of underactuated intelligent ships with unknown time-varying environmental interference and limited position and speed. This approach aims to improve the control accuracy and response speed of the system. First, in order to handle the challenging challenge of controller design, the mathematical model is modified using differential homeomorphism transformation with an eye toward the underactuated properties of ships. Second, the tangent BLF is developed to realize the constraint of the ship’s location and speed error and guarantee the system’s safety by building the time-varying constraint border with exponential decay. When combined with DSC technology, the 'differential explosion' problem, which is common in the backstepping design process, is solved. On this premise, the extended state observer (ESO) is used to estimate and correct for the unknown time-varying disturbance. Lyapunov stability theory proves that the closed-loop system is stable, and the closed-loop signals are bounded. The simulation results show that the suggested control approach has a faster response time than the classic backstepping method and can provide safe and stable autonomous berthing of ships while meeting the limitations, indicating good engineering practicality.