This chapter presents an artificial potential field (APF)-based online collision avoidance system for manned and unmanned maritime vehicles, which is capable of reacting to static and dynamic obstacles in the vicinity. The standard marine `rules of the road' are integrated into the collision avoidance framework. A risk assessment module is also introduced which is based on the standard closest point of approach (CPA) method. A decision maker then selects appropriate rules based on relative heading and positions of the vessels. For the detection part, an integrated vision and laser-based system has been developed to provide sensing functionality for multiple obstacles. Autonomous craft are preferred over manned vessels in scientific operations as they are more suited for long enduring and tedious missions in dangerous or hazardous environments. The technique presented is fairly generic and is applicable to a general class of marine vehicles ranging from a small/medium-sized craft to a large freighter or an oil tanker. The small/medium-sized vehicles have been widely employed in surveillance and scientific missions. For surveillance missions, deploying autonomous vehicles will maximise the coverage and reduce the number of personnel involved in the operation area. Simulation results are provided to include the three fundamental collision encounter scenarios, that is, overtaking, head-on and crossing. It is also shown that Dubin circles could be successfully employed to take the dynamics of the craft into account, which provides a general method independent of the craft size.

Chapter Contents:

• Abstract
• 3.1 Introduction
• 3.1.1 Motivation and background
• 3.2 COLREGs
• 3.3 APFs
• 3.4 Collision risk assessment
• 3.5 COLREGs decision maker
• 3.6 COLREGs zones for APF adaptation
• 3.7 Simulation results
• 3.7.1 Path dynamics
• 3.8 Discussion and concluding remarks
• Acknowledgement
• References

Inspec keywords: remotely operated vehicles; mobile robots; marine vehicles; collision avoidance

Other keywords: risk assessment module; multiple obstacles; manned vessels; laser-based system; integrated vision; collision encounter scenarios; autonomous craft; scientific operations; standard marine rules; scientific missions; autonomous vehicles; static obstacles; surveillance missions; marine vehicles; artificial potential field-based online collision avoidance system; standard closest point; collision avoidance framework; unmanned maritime vehicles; manned maritime vehicles; dynamic obstacles; maritime vessels

Subjects: Marine system control; Mobile robots; Spatial variables control; Telerobotics