Long Weekend Data Testing

AMOS was once again crammed into our van along with 5 people, a dog, and a cat to visit my parents this past New Brunswick Day weekend. I was hoping to try out the air propeller cage that I had "created" by ripping apart a regular fan cage so that it only had about half of its original wire spokes. Even this reduced cage seemed kind of heavy, and I wasn't sure how well it would work atop the small servo motor.

On Saturday morning, I got a chance to try it out on a planned 7 km round trip journey. Unfortunately it only made it 2.4 km out before the wind picked up (maybe ~ 20 km/hr) and AMOS started to have trouble steering. The difficulty initially was mostly to do with software; basically the algorithm would provide a short burst of air power to either the left or right side, depending on the desired turning direction, and then it would wait for the boat to glide into the correction orientation. This had been proven to work well in calm waters, but happened to be insufficient for windy conditions with waves. After spending about 5 minutes swinging the propeller and fan cage back and forth, the lever arm connected to the servo motor slipped relative to the motor shaft (its gear teeth were later seen to be badly stripped) and the propeller swung around backwards. So I paddled over, flicked off the switch, hooked up a rope, and towed AMOS back to the cottage. During those 2.4 km, AMOS did manage to acquire some interesting data with its temperature, pH, and turbidity sensors. This data can be seen on a public arc-gis website here: https://arcg.is/18XbjH. Viewing data for all 3 sensors at the same time on the map is a bit confusing, so I created screen captures of each of the sensors separately:

The westernmost pH value is erroneous, as I had forgotten to remove the cap on the pH probe for that measurement. The turbidity measurements, are simply expressed in volts of received light level, so higher turbidity corresponds to a lower voltage value. Slightly east of the long road on the map, I believe there is a pipe emptying into the ocean. That might account for the higher turbidity, higher temperature, and slightly reduced pH at that location.

The next day, I modified the software to improve the turning function. It did seem to work pretty well for getting AMOS going in the right direction while waves were pushing it up against some rocks. About a minute later though, it appeared that the software on AMOS had crashed, as the propeller stopped turning and it slowly floated toward Prince Edward Island in a ~ 25 km/hr offshore breeze. I paddled out to rescue it, and then later looked at the log file to figure out what had happened. It turned out that the Android phone I was using to set it up had inadvertently sent out a 'q' character over the dying Bluetooth connection, at just about the point where AMOS went out of Bluetooth wireless range. 'q' was the character used by the AMOS software to quit running. I have since changed this so that the user now has to type the word "quit" before the AMOS software executes its quit function.

I have decided to get rid of the heavy metal cage. Some protection is still required for the propeller, although it doesn't necessarily have to be affixed to the propeller mounting, weighing down the servo motor. Instead, I'm going to try mounting a chicken wire cage to the surfboard itself, to form a sort of perimeter fence around the propeller. If AMOS didn't look like a redneck robot boat before, it certainly will now with the chicken wire fence around its back end. 😜