Design and Fabrication of a Small Test-bed Aimed for Basin Experiment of Underwater Multi-agent System

The underwater multi-agent technology using many types of underwater robot has great potential for various underwater activities in the near future. To realize the underwater multi-agent system, we must experience many situations and problems to be solved in that development by using real systems as well as the computer simulations. So we are now building basic systems of basin experiment for the development of AUV multi-agent behavior. In this paper I will introduce our concept of the underwater multi-agent application in the near future and the hardware/software design of our laboratory's AUV small test-bed, precise ultrasound ranging system and LBL coordinate detection system now we are developing. We designed a small thruster which is composed of a 4.5W coreless motor with planetary gear and a rotary encoder. We designed and fabricated the magnet coupling for watertight seal of the thruster to reduce the production cost. The total weight in air is about 3kgf. So the total size is small (0.4m[L]_ 0.4m[B] _0.2m[H]) that we can handle it easily and many robots can swim in our basin(6m[L]_3m[B]_3m[H]). The hull is designed to bear the pressure at least 10m water depth. We selected Lithium ion battery for power supply and the total capacity is 450Wh. By power consumption calculation we may use it about 2 hours with one full charge of the batteries. The main PC is PC104 module (Advantech PCM3350) of which MPU is NS-Geode 300MHz and 64MB RAM. I implemented the Linux based program system in 1GB compact flash card from which the system boots. It controls the total system through PIC based subsystems. An electric compass TCM2 is used to detect the heading angle and roll, pitch. Each device like electric compass has its own PIC and all serial communication line is multi-dropped using RS232 through the communication interface PIC. The 6 underwater connector are attached for ultrasound transducers, thrusters, power supply and ethernet. As we mounted a wireless CCD camera inside, we can see the underwater image as far as the robot is near water surface.