Review of Autonomous Undersea Vehicle (AUV) Developments 
a four-fold improvement in energy available. Ultimately, lithium batteries will be installed for an 
improvement of more than twelve-fold in energy, compared to the present lead-acid cells. 
In order to accomplish its scientific objectives and ensure vehicle safety, ABE must have reliable 
and precise navigation and control. Two complementary navigation systems that are already 
proven in previous deep-ocean operations have been selected. Medium-frequency (10- to 14- 
kHz) transponders, identical to those used for ALVIN, guide ABE during descent to its worksite 
and are used to navigate for surveys over long distances. With this navigation system, ABE has 
the ability to follow tracklines with repeatability of several meters. 
At the worksite, ABE switches to broadband 300-kHz transponders to navigate precisely over 
ranges of about 100 meters with a repeatability of several centimeters. This system (EXACT) 
has been demonstrated on the ROV Jason at Endeavour and Guaymas Basin vent sites. With 
two navigation hosts on the vehicle and two transponders, ABE can obtain a range and bearing 
from either transponder, or it can obtain a long baseline fix when ranges to both transponders 
are available. In on-going dockside tests, ABE demonstrated the capability to hover and follow 
tracklines within several tens of centimeters, and most importantly, to return to its docking 
mooring. In addition, ABE's power consumption during closed-loop maneuvers falls well within 
previous estimates. 
In spring 1993, as soon as it was mechanically complete but before the navigation system was 
installed, ABE was taken out on the ATLANTIS II during a series of ALVIN engineering dives. 
An anchor was rigged on 60 meters of line below ABE, and the combination was allowed to 
free-fall to the seafloor at a depth of 1600 meters. After reaching the bottom, ABE exercised its 
seven thrusters one at a time, recording the rpm resulting from the varying torque commands. 
This tested the control system, internal communication bus, power system, and all the thrusters. 
At the end of the test, ABE released its anchor and freely ascended to the surface. ABE's 
progress was monitored by measuring the range to one of its two built-in transponders. It was 
quickly located on the surface. 
Since then, ABE's capabilities have grown and it was taught to perform increasingly involved 
tasks. In summer 1993 it performed brief autonomous missions using dead-reckoning 
navigation. The video system and the EXACT navigation system were added in fall 1993. The 
navigation system is currently performing well and allows ABE to hover (holding x,y,z and 
heading) in strong tidal currents with only a few centimeters of wander. Forward or sideways 
movements can be commanded, and ABE executes them smoothly. In addition, ABE can find 
the beacon that marks its docking mooring, turn toward it, and dock. 
In June 1994, ABE was shipped to join the ATLANTIS II in San Diego, again in conjunction with 
a series of ALVIN engineering dives. ABE's capabilities to conduct repeated dockings, follow 
tracklines within the ALVIN transponder net, and capture images at specified locations were 
demonstrated. 
The first real science mission occurred in mid-1995, when ABE was used to conduct a complete 
magnetometer survey over a lava flow, known to have erupted in July 1993 along the Coaxial 
Segment of the Juan de Fuca Ridge. A previous survey conducted from ALVIN indicated the 
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