Overcoming constant ocean current disturbances in underactuated AUV path tracking control

In complex marine environments, the path tracking control of autonomous underwater vehicles (AUV) is a critical technology for accomplishing specific tasks.To save energy costs and enhance reliability, most AUVs adopt an underactuated mode. However, factors such as unknown environmental disturbances, highly nonlinear and strongly coupled AUV models make the path tracking problem of underactuated AUVs quite challenging. This paper fully considers the motion characteristics of the AUV and establishes the mathematical model of the underactuated AUV based on the inertial coordinate system and the motion coordinate system. It introduces the influence of ocean currents and utilizes the relative velocity of the AUV under the influence of ocean currents in the improved integral-separated controller, which is more suitable for engineering measurements compared to absolute velocity. In terms of path tracking, this paper transforms the tracking of desired trajectories problem into an error stabilization problem for nonlinear systems by using rotation matrices to transform the dynamic model. It establishes a complete error differential equation. Through simulation verification, the controller can partially overcome the influence of ocean currents, meet the heading requirements and performance constraints, track the desired trajectory, and maintain trajectory motion throughout the process.