Flexible Underwater Ribbon Cable Guide

 The previous rigid 3-D printed shell that was used to join the underwater WeatherBox to the main electronics box on the AMOS surfboard needed to be replaced with something flexible that could flex and swing out of the way whenever underwater obstacles were encountered. 

Some inexpensive plastic tubing was purchased at Home Depot, and 3-D printed adapter parts were constructed for either end of the tubing, to join it to the WeatherBox at the bottom end and the main electronics enclosure at the top end. 

This made a nice, water-tight conduit for the camera cable to follow, but it proved to be difficult to design the top piece to be strong enough to withstand large bending moments that were produced whenever AMOS passed over a shallow, rocky area. Three different top-piece designs were fractured in separate field tests before switching to a slightly different design using a large cable gland at the top. Instead of fitting the top end of the tube over a 3-D printed male plastic piece, the top end of the tube was fitted inside the cable gland. A small amount of heat treatment with a heat gun was applied at the top end of the tube to allow it to compress slightly and ensure a snug fit. 

This design worked perfectly: it had enough "flex" to be able to swing up out of the way of obstacles, without putting too much stress at the top cable gland connection. Here is a video of AMOS crashing into an underwater rock. The WeatherBox and its cable guide swung out of the way and were undamaged:

I enjoy combing through the videos from these tests, looking for fish. Here were a couple that were briefly captured in the most recent test yesterday (October 6):

My favorite clip came at the end of the test when AMOS was just floating near a partially submerged tree. I really like how the light from the sun is shining on the tree in this video, it looks kind of magical:

AMOS Captures Some Fish

 Things have been busy lately, and there hasn't really been much occasion for taking AMOS out in the field. Over the last week though, I was able to develop some software for saving 30 fps 1920 x 1080 video files on AMOS, while still continuing to do all of its regular navigation and data saving stuff. Testing and debugging was done in the pool, and everything seemed to be working well. 

This morning I took AMOS out to Kelly's Creek to test how the navigation, sensor data saving, and video recording all worked together. I was worried that the addition of the video recording in a real environment would slow down the other functions, possibly resulting in sluggish handling or missed data samples. Everything seemed to work pretty well though, although when I had plotted the course the night before, I had not realized how low the water level actually was. The waterline was about 10 m in from where it appeared to be on the ArcGIS map that was used to setup the course. Unfortunately, the WeatherBox  that housed the camera underneath AMOS struck a rock at full speed, and the 3-D printed extension piece that connected it to the main electronics enclosure snapped under the strain. The WeatherBox was quickly flooded, but I was following close behind in the kayak and was able to turn off AMOS's power switch a few seconds later. Clearly a more flexible extension piece will be required here. Perhaps something like a short rubber hose could work?

Despite this accident, the rest of the test was a success. Depth, temperature, and conductivity data were all recorded normally, AMOS navigated itself normally, and 9 video files were recorded, mostly of air bubbles and river vegetation, but at 1:10 of the video below, you can see 3 small fish swimming by for a few seconds:

The end of the above video is where the WeatherBox struck the rock and the camera module was flooded. Unlike the last camera flooding which occurred in salt water, this one was in fresh water, and after storing the camera module in a bag of desiccant for 12 hours, it was confirmed to be unharmed. 

AMOS Looks Underwater

 Last month's assumption that the o-ring seal on the WeatherBox required improvement proved to be correct. The printed part had tiny imperfections underneath the o-ring that allowed water to slowly leak through. A WeatherBox customer who was using it to observe a muskrat underwater came up with a brilliant solution: he found that using some marine goop (ex. https://www.homedepot.ca/product/amazing-goop-marine-109-4-ml-3-7-oz-/1000183125) in the channel holding the o-ring worked to fill in the small imperfections in the plastic and create a watertight seal. I've built a few WeatherBox enclosures since then with the channel filled with Marine Goop and they have all worked quite well.

To take pictures and video underwater with the 6 foot AMOS surfboard, an extension piece was required to get the WeatherBox below the waterline. The bow of the surfboard where the camera is located is pitched upward at about a 20 degree angle, so this requires a curved extension piece. The creation of this extension piece required a couple of weeks. At first, rendering the model in OpenSCAD took days for my laptop to finish, although later iterations of the model used some 2-D optimizations with extrusions that shortened the rendering time to about 24 hours. The first two model attempts also had small gaps on the side with the largest radius of curvature, which led to leaking. Eventually a working model of the curved extension piece was created:

The extension piece was fitted on AMOS and used to capture this underwater backyard pool video:

Apologies to viewers for the acting talent used in the above video. In Nature Robotics operates on a tight budget. 😉

Coming up next week is the final round of  the 2021 edition of the Ocean Startup Challenge (https://oceanstartupproject.ca/challenge/). In Nature Robotics is in the mix again this year, and will be pitching on Thursday, September 9. 

Drip, Drip, Drip, How to Make a Watertight Window?

 Some work has been done over the last couple of weeks on trying to adapt the WeatherBox to function as an underwater camera enclosure. This work has been educational but not entirely profitable. Some underwater tests had been done in the pool, and at the time appeared to be successful, but they were too short (less than 5 minutes) to really prove out the leak-worthiness of the enclosure.

A longer test in a real-world environment confirmed that the enclosure leaks too quickly to be of any use for underwater pictures or video. A slightly modified version of the enclosure with a longer stem was attached to the underside of AMOS and used to record a video frame every second, for a 1 hour test along the shoreline in Cap Brule, New Brunswick. The stem was not really long enough to keep the camera underwater all of the time, and the mounting pins inside this particular enclosure had snapped off, so the camera board was not properly centered. The camera software uses an auto-brightness adjustment, which I think was confused by the alternating views above and below the water. 

The camera ceased to function after about 20 minutes of operation. When the boat was taken out of the water about an hour later, it was half-full of sea water. The camera board was immediately rinsed and dried off, to no avail. A subsequent test confirmed that it no longer functioned at all. 

Some decent depth, temperature, and conductivity data was collected for the test, showing a nice correlation between the 3 parameters: the shallower water was warmer and had a higher measured conductivity.

 Conductivity

Depth

                                                                        Temperature

Here is a video created from stringing the individual 1 Hz video frames together and increasing the playback speed by 5x. Not much to see really, just a lot of bouncing up and down and the occasional piece of seaweed:

I'm going to test out some changes to the camera enclosure cap this week; at this point it looks like the weak point is the O-ring seal with the enclosure window. 

Ocean Startup Challenge!

 There was a big announcement today for In Nature Robotics: we were one of 31 companies out of 158 applicants to be picked for the next round of the Ocean Startup Challenge: http://www.oceanstartupchallenge.ca/announcements/. Starting this Friday, there will be a week of presentations and workshops to get ready for a final pitch presentation, sometime between September 22 and September 24. The 31 companies will be competing for 10 prizes of $25k plus in-kind support. It seems sort of similar to what we went through back in May for the Volta competition; except more of an overall ocean theme. 

I took a couple of days off from AMOS this week to go on a fun family camping trip at Spednic Lake. It would have been nice to try out AMOS there, but the van was packed tightly to the roof with camping supplies, so it wasn't possible. I did manage to get some 3D models of the new WeatherBox put together and tested for water-tightness though. Here is a picture of the component parts (no more little nuts or bolts required!!!) and a picture of the put-together unit (minus the interior locking piece):

The only thing that needs to be modified is that the camera board is recessed a bit too far inside the enclosure, so that you can see tiny smudges of black (from the enclosure) in the corners of the field of view:

(Please ignore the terrible state of this lawn. 😀)

To fix this, I can try to either (i) elevate the level of the camera board inside the enclosure, or (ii) trim down the thickness of the enclosure a bit. 

I have also been working on re-wiring the electronic speed controller (ESC) to situate it behind the propeller. Unfortunately though, I think I may have broken one or more of the wires going into either the ESC or the propeller motor today, as it was functioning sporadically, depending on how I moved the wire around. I'll try a replacement motor tomorrow, and if that doesn't work I'll try replacing the ESC.

Back From The Wilderness

 Avid readers of the blog may have noticed that there was no entry last week; that was the first time in over 2.5 years that the weekly update was missed! Without going into too many details, a long 15 hour bike ride through New Brunswick trails and back roads turned into an even longer 24+ bike ride due to some navigation errors that resulted from poor preparation (forgot 1 phone charger and the other 2 chargers that were brought were not charged, did not bring a printed map (only printed directions), and did not bring proper equipment to change a bike tire, which turned out to be necessary for the last 50 km or so). After being rescued and returned to safety, I was in no condition to think about the blog, and thereby felt justified in skipping a week to catch up on some sleep. Many thanks to Kelly and Dad for searching for us and rescuing us after this misadventure. 

The last time I had AMOS out for a test run was on August 22 at Kelly's Creek. One thing I happened to notice around the middle of this test was that the air propeller motor would sometimes audibly switch down to a lower speed, resulting in a somewhat lesser thrust. Going with the wind the reduction in thrust was not an issue, but on the return trip it was. Some testing in the backyard the next day revealed that the electronic speed controller (ESC) board output power became significantly less when it overheated. Currently, the ESC is sitting in the bottom of the back electronics enclosure, with the battery and a bunch of other electronics, so it makes sense that it could get pretty hot, especially if the weather outside is sunny and warm. By positioning the ESC outside the box, behind the propeller in the airflow however, the output power remained stable, presumably because the ESC was sufficiently cooled. Apparently drone makers know this already; there are instructions available on the Internet for applying a silicone conformal coating to the ESC board to protect it against moisture. The weather is starting to get cooler here, so I might not notice the overheating effect in future tests, but I think I'll re-wire things to put the board outside behind the propeller anyway. 

 Efforts are currently underway to re-design the WeatherBox (i.e. the waterproof enclosure for the camera on AMOS). I would like to get rid of the nuts and bolts and just have a window cap that screws directly onto the enclosure. This would make assembly a whole lot easier, and should look better too. Here are 3D printed versions of the base enclosure piece and an initial window cap (without the plexiglass window) screwed together:

This past week was Jata's last as an intern at In Nature Robotics. One of her projects was an online 3D modeling / ordering tool for AMOS. I have been trying to teach myself 3D modeling using TinkerCAD and other 3D tools to continue her work, but so far have not had much luck. Importing and exporting with these tools tends to do unexpected things to the models. Possibly it is just user error though!