An Autonomous Navigation System for Unmanned Underwater Vehicle

Autonomous underwater vehicles should possess intelligent control software that performs intellectual functions such as cognition, decision and action, which originally belong to the ability of domain expert, since the unmanned underwater robot is required to navigate in hazardous environments where humans do not have direct access to. In this paper, we suggest an intelligent system architecture called the RVC model, which can be applied to various kinds of unmanned vehicles. The architecture consists of the collision avoidance system, the navigation system, and the collision-risk computation system. The RVC architecture is devised to make use of artificial intelligence techniques, and to provide the subsystems structural and functional independency. The collision avoidance system adopts a new heuristic search technique for the autonomous underwater vehicles equipped with obstacle avoidance sonar. The fuzzy relation product between the sonar sections and the properties of real-time environment is used to decide the direction for the vehicle to proceed. The simulation result leads to the conclusion that the heuristic search technique enables the AUV to navigate safely through obstacles and reach its destination goal with the optimal path. The navigation system executes the offline global path planning for the AUV to guarantee the safe and efficient navigation from its start point to the target destination. The system also does the duty of monitoring and controlling the vehicle to navigate following the directed path to destination goal. The collision-risk computation system produces a degree of collision risk for the underwater vehicle against surrounding obstacles using information from the circumstances, obstacles, and positions. The degree is provided to the collision avoidance system as one of the decision tools used for safe avoidance with the obstacles. A 3D simulator is developed to test the AUV navigation system based on the RVC model. The goal of the simulator is to serve as a testing ground for the new technologies and to facilitate the eventual transfer of these technologies to real world applications. The simulation system consists of an environment manager, objects and a 3D viewer. Objects model all physical elements such as the map, obstacles and the AUV. The environment manager plays the role of an intermediary, which allows created objects to interact with each other, and transmits information of the objects to the 3D viewer. The 3D viewer analyzes the received information and visualizes it with 3D graphics by using OpenGL primitives. O pe n A cc es s D at ab as e w w w .in te ch w eb .o rg