Abstract

This paper deals with the problem of modeling an underwater tethered vehicle with highly coupled dynamics. The goal is to develop a simple yet effective system model that can capture the significant coupled dynamics between interconnected rigid and very flexible bodies in the system over a wide range of ROV applications. In the formulation of ROV-tether connections with higher-pair DOF, constraint Jaco-bian matrix and a quadratic velocity vector always lead to numerically-expensive forms when rotational parameters are used combined with a fully-parameterized ANCF (absolute nodal coordinate formulation) tether element. These issues are addressed and kinematic joints associated with the common tether connections are presented. An alternative formulation is proposed to overcome these issues, and its applicability is assessed through validations with a basic experiment.

Introduction

The deep regions of ocean space have always been the particular frontier explorations to the human races. As science and technologies have never ceased to evolve, continuous explorations by humans to extend their accessibility in the deep oceans, which were, until recently, beyond the scope of our explorations, are demanding a drastic increase in the deployment of underwater vehicles such as AUVs (Autonomous Underwater Vehicles) and ROVs (Remotely Operated Underwater Vehicles) in the deep oceans. ROVs are used for inspection, maintenance, and repair (IMR) operations while AUVs are mostly used for monitoring or search and rescue (SAR) applications due to autonomous capabilities with their reliance on sensor technology and their high maneuvering speeds. ROVs are unoccupied, highly maneuverable underwater robots remotely operated by a human pilot aboard a surface vessel. A tether cable serves as a physical link between the operator and the vehicle. One of the distinguishing features of the tethered ROVs is that they incorporate the real-time telepresence to give the operator a sense of being in the place of the vehicle. ROVs can be upgraded by mounting additional equipment to expand the vehicle's capabilities. Providing the real-time data telemetry, maneuverability and continuous operations for many hours, the underwater tethered systems have become essential tools in deep sea's explorations.

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