Design of a small, multi-purpose, autonomous surface vessel

The continued development of unmanned underwater vehicles (UUVs) has also brought about new complex missions that the vehicles must perform. Such missions include mine counter measures (MCM), underwater system inspection, route surveying, and oceanographic sampling. More recently, a growing need for missions to be performed by multiple vehicles has emerged. An important task in being able to perform such a multi-vehicle operation is for each vehicle´s position and orientation to be precisely known and updated to onboard sensors, in real-time, maximizing the surreptitious capabilities and quality of the data. Without this high quality navigation data, the mission performance is poor and little confidence can be given to the results. Currently, UUVs can use inertial navigation systems, coupled with Doppler velocity loggers (DVLs), for navigation. However, inertial navigation systems are large, high-power, and expensive, while DVLs have limited bottom-tracking range. Some UUVs are equipped with global positioning systems (GPS), however the vehicle must surface to establish either a RF or satellite communication link. A solution, to increase the accuracy of a vehicle´s position is the use of a surface vessel, notably an autonomous surface vessel (ASV). One such vehicle is currently under development by the Department of Ocean Engineering at Florida Atlantic University. The ASV is being built upon an existing surface vessel navigation and control package, a vertical communication and US BL navigation system derived from the FAU-Dual Purpose Acoustic Modem and 3D motion compensation algorithm that utilizes a low cost GPS/IMU/COMPASS/ADCP system. The accurate positioning system onboard the ASV uses an acoustic uplink system between the ASV and UUVs below, to provide the UUVs with the navigation information needed for a successful mission. The development of the ASV presents several problems such as controlling the vehicle, so that it can operate autonomously, gathering t- > - > he sensor information, and passing the information to the UUVs below, in real-time. The control of the ASV can be divided into software and hardware components. On the software side, Simulink, part of Matlab, allows a user to develop a controller for the ASV by using a friendly graphical user interface (GUI). Matlab also allows for a host to target communication, either through RS-232 or TCP/IP, by using a toolbox called xPC Target. This setup allows the controller to be developed and compiled on a personal computer, the host, and then downloaded to a PC-104 stack inside the ASV, the target. Simulink blocks can also be created to control the flow of information from the sensors to the PC-104 stack, whether the sensors are connected via an AD/DA board or through serial ports using RS-232 communication. While the ASV is designed to give UUVs a more accurate position without installing expensive equipment on each of the UUVs, it can also be used so that a user can monitor the progress of a mission. The communication from the user to the ASV is also accomplished using xPC Target´s host to target communication using a wireless link, and from the ASV to the UUVs using an acoustic modem. By using a surface vehicle, the mission performance of a group of UUVs can be improved by providing accurate and up-to-date positioning as well as by allowing a user to change the mission on the fly, without having to recover the UUVs.