Path following for an autonomous underwater vehicle (AUV) by using a high-gain observer based on an AUV dynamic model

In this paper a curved path following problem for autonomous underwater vehicles (AUVs) moving in a nonuniform ocean current is presented. A high-gain observer (HGO) based on an AUV dynamic model was used to estimate three dimensional current velocities. The current velocities were determined by calculating the differences between the vehicle’s absolute velocities and the vehicle’s relative velocities estimated by the observer. The HGO was chosen as a nonlinear estimation algorithm, and the observer gain was computed by solving a Linear Matrix Inequality (LMI) which represented the estimation error dynamics. The desired curved path was represented by using a Serret-Frenet frame which propagated along the curve. The path-following system includes a guidance law, un update law and a proportional and integral controller. Two cases of numerical simulations were conducted to verify the performance of the path following system.