In this paper we present the concept of a multi-AUV system interconnected by a smart cable that contains 3-D positioning sensors for rapid inspection of large underwater structures in a limited mission timeframe. The smart cable provides not only the position of the end-points (AUV locations) but also its own shape in real-time, while also acting as a communication link between AUV. Using this cable, we propose the Hand-in-hand System (HS) for AUV localization and development of an obstacle avoidance strategy to accomplish the given task. For the application of the smart cable under water, versatile tank tests and field experiments were carried out to demonstrate and confirm the efficiency of the proposed system.

INTRODUCTION

Marine structures such as bridges, dams and ports play an important role in daily life, and this requires that routine inspection and maintenance work be carried out in dangerous underwater environments. Robots can undertake these tasks more accurately and efficiently than humans while eliminating risk to human life (Ura, 1994). In view of the introduction of robots, underwater structures-related tasks can be classified into 2 groups: construction/repair and inspection.

  • Construction/Repair. These tasks require powerful robots with complicated maneuvers and dexterous manipulations to be carried out; thus the human interface and power transmission via a tether cable offered by ROV (Remotely Operated Vehicles) mean that they can effectively undertake such tasks.

  • Safety Inspection. Most safety inspection tasks involve collecting data such as taking photos of the targets and their environment, which are spread over an extensive area. Such tasks require excellent maneuverability as opposed to intelligence.

Since most underwater structures are public facilities and are difficult to stop long-term for inspection tasks, the tasks require a shortened mission time. We propose a multi-AUV (Autonomous Underwater Vehicle) system for the tasks.

This content is only available via PDF.
You can access this article if you purchase or spend a download.