Monterey Bay Aquarium Research Institute
Autonomy
T-REX 3rd Sea Trial
3rd T-REX sea trial


On September 21st 2007, the Autonomous System group undertook a full day cruise to further validate the work undertaken so far on T-REX, the onboard deliberative control system on MBARI's CTD AUV platform.  The role of planning in this field trial was to reactively generate commands to the Vehicle Control Sub-system based on feedback from the vehicle and to proactively generate plans based on science and operator objectives. The agent dispatches commands to the vehicle and synchronizes updates from the vehicle with the expected state of the plan.

Our objective this time was to execute a full science mission. By doing so we wanted to demonstrate that T-REX can scale for long durations missions, to stress it so it could replan more frequently and to observe the impact of critical situations in term of system performances and mission  behavior.

The data below summarizes the two most representative runs on this day. While we undertook some safety checks to ensure that modifications to our code base did not have impact on safet, the duration of the science mission (in excess of 3 hours) limited us to prolonged experimentations.

Our results for this day are summarized as follows.

T-REX reaction to stressing situations

The goal of this mission was to undertake 3 different transects :
  • from westNode to northNode with a priority of 3
  • from farWestNode to southNode with a priority of 1
  • from eastNode to centerNode with a priority of 2
and then wait for pick-up at the centerNode. This mission was similar to the one which failed in trial #2 except it had an extra science goal. T-REX was able to determine and execute a plan including all the goals as also to adapt to offnominal situations.

Plan execution:

date Command Max. duration
6 setpoint 5
11 descend 71
61 waypoint 132
133 waypoint_yoyo 105
241 ascend 71
281 getgps 598
319 setpoint 5
324 descend 71
363 waypoint_yoyo 135
444 ascend 60
458 waypoint 98
559 ascend 72
598 getgps 598
631 setpoint 5
636 descend 71
682 waypoint 186
872 ascend 71
917 getgps 598
950 setpoint 5
955 descend 71
1005 waypoint 90
1041 waypoint_yoyo 146
1190 ascend 72
1229 getgps 598
1263 setpoint 5
1268 descend 71
1313 waypoint_yoyo 185
1464 ascend 36
1474 waypoint 26
1503 ascend 69
1538 getgps 598
1580 setpoint 5
1585 descend 71
1638 waypoint 179
1803 descend 14
1821 ascend 75
1901 getgps 598
1939 setpoint 5
1944 descend 77
2000 waypoint_yoyo 172
2147 exit
Mission path(2D) Mission path(3D) T-REX CPU usage

A Science mission

The objective of this mission was to reproduce a run already executed using the nominal prescripted layered-control approach, but doing so using T-REX. The mission selected with the help of John Ryan of MBARI, was a volume survey off of MBARI's M0 mooring. The goal was to make a Yo-Yo survey from the initial point to the pick-up point and then wait for the pick-up. As our path network had only one path between these two points,  T-REX was able to find this path and then plan and execute the mission accordingly with insertion of check-in windows every 1700 to 1800 sseconds consistent with its domain model.

Plan execution:

date Command Max. duration
6 setpoint 5
11 descend 71
67 waypoint 80
99 waypoint_yoyo 1699
1794 ascend 97
1865 getgps 598
1900 setpoint 16
1919 setpoint 5
1924 descend 60
1964 waypoint_yoyo 160
2080 waypoint_yoyo 403
2442 waypoint_yoyo 59
2490 waypoint_yoyo 1226
3715 ascend 97
3790 getgps 598
3824 setpoint 19
3846 setpoint 5
3851 descend 60
3883 waypoint_yoyo 720
4599 waypoint_yoyo 404
4978 waypoint_yoyo 665
5644 ascend 77
5684 getgps 598
5718 setpoint 18
5739 setpoint 5
5744 descend 60
5777 waypoint_yoyo 988
6721 waypoint_yoyo 60
6767 waypoint_yoyo 400
7157 waypoint_yoyo 379
7538 ascend 95
7601 getgps 598
7636 setpoint 16
7655 setpoint 5
7660 descend 60
7689 waypoint_yoyo 1482
9168 waypoint_yoyo 284
9455 ascend 62
9521 getgps 598
9560 setpoint 5
9565 descend 60
9600 waypoint_yoyo 161
9715 waypoint_yoyo 1642
11354 ascend 73
11400 getgps 598
11436 setpoint 16
11455 setpoint 5
11460 descend 60
11487 waypoint_yoyo 161
11619 exit
Mission path(2D) Mission path(3D) T-REX CPU usage Processed science data

The mission duration was approximately 3 hours and the performance of the system was comparable to what we had seen in prior trials as illustrated in the CPU performance graph above further validating the scalability of the system in terms of plan size and mission duration.

The CPU data indicates 2 spikes in the cost of synchronization. Analysis of the log files indicates that these spikes correspond to plan failures of the form encoutered in the prior sea trial due to squeezing of uncontrollable durations. This time, the agent simply repaired the plan which explains the increased cost of synchronization. This repair capability has been the key to improving the robustness of the system over the prior sea trial.

On the 2D path, one can see the vehicle has interrupted its science survey to localize at the surface on 6 occassions. This is indicated by the blue colored sections which correspond to GPS hits. The mission progresses from the north-west and finishes at the south east. The northward deviation on ascent to localize is a navigational error due to a bug in the model. Not withstanding this error, the vehicle navigation was correct and confirmed that the compass can be relied on to make heading changes without surfacing.

Also shown is the data processed from this run using MBARI's SSDS Data Portal. Many thanks to Mike McCann for handling this.

This mission set a new at-sea endurance record for T-REX by an order of magnitude, with no adverse effects on system performance. Our focus for future missions will emphasize greater application level functionality in pursuit of interesting science observations

Last updated: Feb. 06, 2009