Improved ESO‐LOS Guidance Strategy for AUV: Theory and Experiment Validation

ABSTRACT To address autonomous underwater vehicle (AUV) path tracking under time‐varying disturbance, this paper proposes an Extended State Observer (ESO)‐based Line‐of‐Sight (LOS) guidance strategy that accounts for time‐varying ocean currents, model uncertainties, and drift angles. The disturbances are treated as a lumped term without assumptions on their magnitude or variation. A kinematic error model incorporating these effects is established, and an ESO is designed for real‐time disturbance estimation and compensation. An adaptive look‐ahead distance is introduced to enhance responsiveness to the AUV's tracking state. A virtual control input is then integrated into the traditional LOS framework to formulate an improved guidance law, forming a closed‐loop cascaded system of tracking and estimation errors. Using input‐to‐state stability (ISS) theory and the cascaded systems theorem, the overall system is proven to be ISS, and the ultimate bound of the cross‐track error is derived under bounded disturbances. The proposed method was compared with several existing approaches in simulations, demonstrating its superiority. Finally, three field experiments were conducted to track straight‐line, polyline, and circular paths, respectively, achieving a mean cross‐track error of no more than 0.48 m across three tested path types and an average estimation error of ESO no greater than 0.0163 m.