Visual Servoing at UNH, Day 2

The day started off very well, with us checking out the mounting pole for a piece of multibeam sonar equipment that was being tested earlier in the week.


Satisfied that the image processing component was working properly, we switched to the 13cm pipe that we would be using for our demo.


Almost immediately, we ran into trouble... all of our calculations for distance were off. We ran and re-ran our calculations for the angular resolution of the camera, and for calculating our distance from the pipe based on its width in pixels on the video.

An hour or 2 later, we noticed that we had accidentally declared our angular resolution as a boolean instead of a double. That's a pretty big error! Surprisingly, it only affected our distance calculation by a factor of ten. But once we fixed it, we were spot on.


The results are dramatic!

Visual Servoing at UNH, Day 1

Today we are at UNH to work on some visual servoing code that Justin wrote. The goal is to be able to follow a vertical pipe, controlling yaw and position based on image processing.


Mike has mounted the camera on the bottom of Odyssey, facing forward so that we will be able to track an object in front of the vehicle.


Early on, we had to re-adjust the aperature on the camera. We had made it as small as possible to increase our depth of field, but it was just too dark in the facility to see anything on that setting. So, we opened up the aperature and double checked the focus.


With the vehicle on an ethernet tether, we were able to use coriander to tweak the settings of the camera once it was underwater. This program makes the tuning stage go very quickly!

REx II is Back in Cambridge

Today, we got the REx II vehicle back from Hawaii.

Due to restrictions on shipping, we didn't bother to send the lithium ion battery by mail. Instead, we just built a new one.


Unlike the battery for Odyssey IV, this battery is designed to fit into the bottom half of a pressure tube. The individual supercells are not wrapped in plastic, but instead squished together to form the full battery.


The electronics fit on top.

Potting: A Mini-Howto

I put a mini-howto on potting on our wiki.

Nantucket Sound Testing, Day 5

Today we did some tests to characterize the effects of our horizontal stabilizing fins on our depth while under way. The goal was to see if we could fly the the vehicle like a plane, changing altitude by changing forward velocity. As it turns out, there isn't a huge effect, even when we pointed them down significantly.


The final recovery worked like a swiss watch.


Taking Odyssey off the boat when we got back was also a very smooth operation.


So long, Mike and Drew!

All in all, a very productive trip.

Nantucket Sound Testing, Day 4

Today some grad students from CSAIL came out to try running some of their planning code on Odyssey.


It was a calm day, so -- combined with the fact that we are getting better at the deployment process -- everything went very smoothly.


One of the students went for a swim, so Justin gave her a tow on the vehicle.


We weren't the only ones towing thrill-seekers around the cove...


We did a lot of dive missions to test out the camera system. The vehicle makes a splash on the surface, then pops up a few minutes later (and our confidence in this process has grown considerably since the beginning of the week). Unfortunately, it looks we will have to focus the camera manually since every picture between 1.5 and 5.5 meters altitude comes out blurry.


This time, Mike Ryan picked up a recovery pole from the WHOI facility, which makes it much easier to clip the crane hook onto the lifting bail. My butt didn't get wet this time, and I was nowhere near falling off the dive ladder.


The rest of recovery is a snap.

Nantucket Sound Testing, Day 3

First thing this morning, we went to get our DSSI thruster fixed at their facility in Falmouth. As we had hoped, there was no damage to the thruster, so they put a new cable on it and we were good to go.


We ran almost nonstop throughout the day, setting up shop on the fly deck so we could get a better view of the vehicle.

That's it, off in the distance.

We made a lot of progress on tuning the PIDs for yaw, although the gains that produce some of our straightest trajectories also produce some of our most spectacular instabilities.


When the mechanical engineers are bored, it means the software engineers are making good progress.