Depth-based pseudo-terrain-following navigation for cruising AUVs

Abstract

This paper presents an approach of depth-based pseudo-terrain-following navigation for underactuated cruising AUVs subjected to near-bottom survey missions. Based on the waypoint-based path planning, our approach provides a set of optimal waypoints by following which a cruising AUV accomplishes an effectual near-bottom flight avoiding bottom collision. In deriving our waypoints, we solve an optimization problem. The problem formulation employs the performance index as a metric for the deviation between the AUV flight trajectory and the along-track altitude envelope of a terrain. An inequality constraint of the minimum allowable altitude is incorporated into our optimization. Moreover, considering the motion-constrained characteristics of a dynamic system, a state–space model describing the motion of a specific vehicle is also incorporated into the optimization. As the solution procedure a GDS-based search algorithm is used. By applying the algorithm, the optimal reference depths of the waypoints predefined within a horizontal plane are obtained. Being a depth-based control approach providing superior angular motion stability, our pseudo-terrain-following navigation is particularly suited to acoustic bottom mapping and imaging. The feasibility and efficacy of our approach are demonstrated through the application of optimal waypoints to an actual near-bottom survey mission using our cruising AUV.