Effect of amplitudes and frequencies on Virtual Planar Motion Mechanism of AUVs: Part II 3DOF implementation, comparison with RANSE and field trials

Abstract

Planar motion mechanism tests have been widely used in simulations, i.e, virtual environments for ocean craft, especially for underwater vehicles. These tests involve a pre-determined sinusoidal trajectory. While there are general guidelines for the choice of amplitude and frequency for such trajectories in existing literature, there are none for smaller submerged ocean craft. The direct application of the work presented in this paper is for autonomous underwater vehicles (AUVs). A series of two articles presents analysis of virtual planar motion mechanism (VPMM) specific to AUVs. An arbitrary selection of amplitudes and frequencies for VPMM can result in significant uncertainty in hydrodynamic derivatives. The results in this article explain the effect of frequencies and amplitudes of pure sway and pure yaw VPMM implemented in a lumped parameter maneuvering model (LPM) for the horizontal plane. This article shows that for typical AUV geometries that the use of non-dimensional frequency up to a value of 0.5 and a non-dimensional amplitude of up to 0.25 remains acceptable for pure sway and pure yaw VPMM despite fluid memory effects. For the first time, a detailed methodology to determine appropriate amplitudes and frequencies for any craft is presented, with the results of one craft shown as an example. Overall, this series of articles sheds light on the process to determine the amplitude and frequency for pure sway and pure yaw VPMM for an AUV in the early design stage.