Explorer1000: A Long Endurance AUV with Variable Ballast Systems

With multi-driven mode including rudder, propeller and variable ballast systems (VBSs), Explorer1000 is designed as a long-endurance Autonomous Underwater Vehicle (AUV) by Shenyang Institute of Automation (SIA), Chinese Academy of Sciences. Explorer1000 mounted two high-precision VBSs on its bow and stern can reach neutral buoyancy, thus maintain constant depth or altitude for a long time. In order to increase endurance, Explorer1000 remains supervision and standby state with neutral buoyancy. At the moment, most of energy-consuming equipments are shut off and only a depthometer, an altimeter and an energy-efficient microcontroller in place of autopilot control unit (ACU) to monitor AUV's safety such as distance from seabed and water leakage, etc. The scheme is able to guarantee AUV to carry out scientific missions over periods of weeks. If Explorer1000 regulates to neutral buoyancy before sailing, it can accomplish cruising with zero angle of attack that minimizes drag and saves energy effectively. Last but not least, Explorer1000 can achieve two observation modes including long-term observation in situ and cruising observation for multiple required sites. The rudder and propeller system is mainly used for most maneuverability in horizontal and vertical plane, while VBSs play a primary role in accurate vertical motion. Recently, Explorer1000 successfully completed one lake trial and two sea trials. In May 2015, Explorer1000 was fitted with Acoustic Doppler Current Profilers (ADCP), Conductivity Temperature Depth (CTD) sensor, Optical Dissolved Oxygen (ODO) sensor, Turbidity (Tu) sensor, chlorophyll sensor and so on and carried out its first field trial in Qiandao Lake of China. In September 2015 and June 2016, Explorer1000 accomplished its two sea trials in Yellow Sea and South China Sea, respectively. In the South China Sea trial, Explorer1000 completed 517 km cruising range at 2 and 3 knots. This paper will describe how we handle the design issues that affect range and long endurance, such as two high-precision VBSs at bow and stern of AUV, a microcontroller to monitor AUV states instead of ACU. Finally, the sea trial results are presented.