Design concept and experimental results of the autonomous underwater vehicle AQUA EXPLORER 2 for the inspection of underwater cables

AQUA EXPLORER 2 (AE2) is the first and only autonomous underwater vehicle in the world which can autonomously track underwater cables and measure their burial depth. Its weight in air is about 260 kg, and its dimensions are 3 m in length, 1.3 m in width and 0.9 m in height. It can swim freely up to 500 m in depth for 24 h continuously. Although the vehicle can communicate with a mother vessel with an acoustic link, only high-level commands are sent to the vehicle and most of the control is done by a built-in computer. When tracking underwater cables, low-frequency current is supplied to the underwater cables. The vehicle can locate and track cables by detecting the magnetic field generated by the current. Since it was first launched in 1997, AE2 has carried out three sea trials and five cable-inspection missions. The total length of inspected cable exceeds 400 km. In 1999, in a real inspection of an underwater telecommunication cable crossing the Taiwan Straight, it was proved that AE2 was robust against current and sand-waves. This paper presents the basic design concept, cable-tracking performance, acoustic links, sea trials and operating results.