Key technologies for AUV "URASHIMA"

A deep and long cruising range AUV (autonomous underwater vehicle) named "URASHIMA" (AUV-EXI; development code name), has been developed by JANISTEC since 1998. URASHIMA can cruise long distance in the sea and collect sea data and water samples automatically for offshore exploration. The dimensions and weight of URASHIMA are 10m (L), 1.3m (W), 1.5m (H), and about 7.5 tons in the air. There are two very important key technologies for a long cruising range autonomous underwater vehicle. One technology is the power source. URASHIMA has two types of power sources. One is a high capacity lithium-ion rechargeable battery. The other one is solid polymer electrolyte fuel cell. With these power sources the vehicle capable of performing long ranges missions. The estimated cruising ranges are about 100 km by using battery and about 300 km by using fuel cell each other at three knots. The other technology is the navigation system. The AUV cruises independently without any communications between the mother ship and vehicle. It is very important to know its present position and forward environment. URASHIMA has highly accurate navigation sensors, such that the inertial navigation system (INS) consists of three sets of ring laser gyro and accelerometers, obstacle avoidance sonar (OAS), Doppler velocity log (DVL) and acoustic homing sonar. The AUV enables long distance cruising independently with these navigation sensors. The sea-going tests started in June 2000. The equipment, hardware, software, and autonomous functions, will be improved gradually. In these sea trials, URASHIMA achieved a dive to3518 m and cruised 132.5 km in autonomous navigation mode.