August  2006  ARL
January  2007  Quarry
February  2007  la Pilita
March  2007  la Pilita
May  2007  Zacatón
Field Notes
Monday, July 31 - Friday, August 4, 2006
Stone Aerospace (SAS) and Applied Research Lab (ARL), Austin, Texas
In this first dive test of the DEPTHX vehicle our goal is to measure and calibrate our thruster models and perform coordinated control of the vehicle. At the same time we intend to confirm sensor models and accurately dead reckon the vehicle's path in the test tank.
Monday and Tuesday were mostly spent debugging. The entire system had not yet been run from the batteries. Electrical problems and low level communications had to be addressed. The team split into three groups; one examined the batteries, another looked at the Doppler Velocity logger (DVL) and a third debugged the thruster controllers (MTS).
By the end of day on Tuesday, many of the electronic and communication issues had been addressed. The vehicle was sealed up and put in the small tank. Once submerged, we distributed weights to balance the robot and neutralize buoyancy. We moved on to a trailer for transport to the Applied Research Labs (ARL) test tank.
On Wednesday morning the robot arrived at ARL. The DVL's power problem was resolved with a slow-blow fuse courtesy of ARL. We dunked it into the tank. The good news: nothing leaked, the fibre optic worked great. The bad news: thrusters were unuseable, IMU didn't align, wireless didn't work. Such problems are routine during initial checkout of a new robot. After some debugging we were able to fire thrusters individually and IMU alignment was worked around.
We conducted our initial system identification tests; firing each thruster and observing the vehicle's response. Thruster debugging continued into Thursday, and by the end of the day we could reliably command individual thrusters in torque mode greatly speeding up the system identification process. We also got an unexpected surprise; 2 of the thrusters had been swapped. Once that had been worked out, we started tuning the thrust mixer.
On Friday we used the crane to drag the vehicle and collect sonar and inertial sensor data. We felt confident in the thruster mixing table and ran the vehicle untethered, collecting more accurate thrust-response data. Finally we pushed the vehicle down to the bottom of the tank, reaching a depth of 9 meters.