Parametric modelling of interacting hydrodynamic forces in 3 DOF for underwater vehicles operating in close proximity

In this paper we present a parametric model of the hydrodynamic interaction forces for two underwater vehicles operating in close proximity. We first review the models for interacting forces in the horizontal plane of surface vessels and empirical approximations that can be potentially applied to underwater vehicles. Then, based on both potential theory and experimentally derived models available in the literature, we propose a partially-fixed model structure of the hydrodynamic interaction forces. This partially-fixed model structure is used for the identification of a full parametric model for the hydrodynamic interaction forces. The data set considered to validate the model represents a fully-submerged hull shape (an enlarged Explorer AUV hull shape) that moves holding its course at a forward speed and another hull shape (a SUBOFF hull of reduced size) that overtakes Explorer in a parallel course. We exploit the novel model structure together with the experimentally validated data to obtain a parametric model of the interaction forces on the overtaking vessel at different transverse separation distances. We estimate the parameters using one dataset and then validate the model for other sets. The results obtained are considered accurate for the intended purpose of the model, which is the future design of a motion control system for the SUBOFF manoeuvring in close proximity to the Explorer.