Hello Reader,

Welcome back to The Build Log! Today, I want to tell you about an unexpected problem we have encountered when testing our DIY autonomous submarine (CPS A). As you might have read, the mission has been quite successful. This is the autonomous submarine in question:

Problem:

During the mission, we were swimming both in:

"Surface mode" - with the submarine swimming very close to the surface with the GPS antenna sticking out,

and "Underwater mode" - with the submarine underwater, close to the bottom of the lake.

The problem is that when the submarine is in the "surface mode" and the main thruster was active, it started heavily leaning toward the right side of the submarine. See the picture for reference:

The issue was caused by 2 things:

• First is torque roll. Torque roll happens in basically any ROV/underwater vehicle that uses 1 thruster, and not for 2 (or more). It's caused by the whole vehicle tilting in the opposite direction of the torque generated by the main thruster.
• The other issue is weight of the antenna itself and the GoPro camera we attached later. That's why the problem is much worse when the vehicle has the antenna sticking out above the surface of the water.

This rotation is a big problem, as it makes steering less efficient, and more errors in the position estimation algorithm - the DVL likes to be operated parallel to the sea bottom.

Solution:

We've come up with some solutions though. The first is just adding additional motors. The second one is using two propellers instead of one. We'll update you soon on which solution we'll decide to go with!

If you want to build an underwater project, the easiest way to get involved is to build the entire CPS 3 drone with our DIY Kit -> now available!

You don't have to buy any components separately, because they're all in the one box delivered to you.

Cheers,

Piotrek, CPSdrone

PS: You can access all of the previous releases of the newsletter here.