Software structure for a simple autonomous underwater vehicle

The control program for an autonomous underwater vehicle is described. The design is based mainly on intelligent control, and to a lesser degree on automatic control principles. The control program enables the vehicle to follow a route determined by a number of waypoints specified in world coordinates. Obstacles are detected and avoided. The main sensor is eight single-beam sonars. The sonars are used to detect obstacles and to determine the vehicle position in an indoor tank (80 m length×50 m width×10 m depth). The vehicle has four degrees of freedom, of which three are used by the control program. The main goal of the system design is to give autonomous systems reliable performance in unstructured environment. Error detection and recovery, incremental increase in functionality and a general approach to the problem of autonomous behavior are emphasized. This leads to a modular design, with the program being divided into modules based on function and abstraction level. All modules interact through a database which keeps track of commands and data passed through the system