Not Quite Invincible

To test out how well (or not) the propeller shields worked as a protection against weeds, the following fairly grungy location at Woolastook was selected for a field trial:

As might be expected, this amount of vegetation was too much. The grass and other plant material plastered themselves against the intake grate, effectively stopping the boat in its tracks. At least the grass did not get caught in the propeller though. Here is a picture of a large clump of grass that hung from the propeller shield after the boat had been dragged through the section pictured above:

AMOS was dragged out beyond the grassy area, and then piloted using the Android app for a while, but after about 10 minutes it died abruptly. Checking the ship log afterward showed that the battery was not well-charged at the start of the test (it had been collecting turbidity data all night long the night before), and manually driving the boat near top speed was enough to make the battery drop momentarily below 10 volts, causing the battery management system to kick in and force a reboot of the Pi computer.

Testing over the past few weeks, it was noticed that the GPS signal would sometimes drop out for periods of time. Unfortunately the antenna cable had stopped working (probably the cable had a break in it somewhere) and it was no longer providing any gain so it was replaced with a new $17 model from Amazon. Testing with the gpsmon program on the Pi showed that the new one provided about 3 or 4 dB of gain.

This past week the Android app has gotten a couple of new functions: "homing" and "picture snapshot":

Homing brings AMOS back to the GPS location of the phone and the picture snapshot function tells AMOS to snap a picture using the camera and send it to the phone.

A second test was performed at a different location in Woolastook to test out the LiDAR. The camera was programmed to snap a picture anytime the LiDAR detected an obstacle within 13 m. There were some initial communication problems during this test, which happened to result in a dramatic crash against some rocks:

https://youtu.be/1HZaNorxaYQ

Luckily nothing was damaged, and after pulling the boat away from the rocks, the test continued. The rocks and my kayak were the only things that the LiDAR detected during this test. The water was quite calm and placid though, so the test should be repeated sometime when there are some actual waves, to see if LiDAR reflection off of waves might be an issue. After this test, some code was added to automatically shut down the thrusters whenever an object is detected within 13 m distance.