Autonomous underwater vehicles (AUV) sensitivity of motion response to geometric and hydrodynamic parameters and AUV behaviours with control plane faults

Abstract

Autonomous underwater vehicles (AUV) are rapidly emerging as an important tool in ocean exploration and maritime defence systems. Reliability is tone of the key issues in making these vehicles viable for scientific, commercial, and military applications. The vehicles must be able to accomplish the mission, or some subset of the mission objectives. -- The research herein is concerned with defining vehicle behaviours in the light of design choices that will result in improved vehicle performance under nominal (fault-free) operating conditions and with guarantees of acceptable vehicle behaviour even with control plane faults. Numerical studies were performed using a computer model of the AUV C-SCOUT (Canadian Self-Contained Off-the-shelf Underwater Testbed). Because it is typical of many vehicles active in the world today, the results are qualitatively valid for a large number of vehicles. Quantifying the behaviours provides a foundation for further analysis of behaviours in various planned and unplanned conditions the vehicle will experience over the course of its active lifetime. -- First, a numerical study was made of the effect of variations of geometry on added mass coefficients. The results demonstrate that intuitive expectations for the effects of geometry on added mass are valid. -- A second numerical study was made of the sensitivity of AUV response measures in turning circles and zigzag maneuvers to variations in hydrodynamic parameters. The results have specific implications for the design of AUV. and provide a baseline of behaviours inherent to the vehicle itself. -- Finally, a numerical study was made of vehicle response during holding course, diving, and turning, while the vehicle is experiencing various angles of jam on each of the control planes, and while the vehicle is missing one of the control planes. This information was used to define the vehicle behaviour, to generate conclusions about vehicle controllability, and to suggest safe operation envelopes for guarantees of mission success. -- The contributions made in this work include a systematic description of the effects of varying vehicle design parameters and hydrodynamic parameters (which result from certain design choices). Also included is a systematic analysis of the effects of control plane faults on the response of the vehicle.