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My (Nearly) Finished ROV Build


(Seth Opgenorth) #1

I’ve been working with a team at my University to build an ROV for the MATE competition, and we’re getting pretty close to having it completely fine tuned. It has a fairly aggressively tuned depth control with an OpenROV depth sensor, is powered off of 48V (through an 80ft 16awg tether), and manually controlled with a PS4 controller over UDP. It also uses two BlueRobotics 4" tubes, with domes, the vent caps, a few penetrators, a lot of SubConn bulkheads, a 3D printed frame, 3D printed Kort nozzles for the bilge pumps (that gives a 60% thrust increase, for the same current!), all electronics PCB’d with connectors for commercial breakout boards, 60Hz UDP communication for all control values/sensor data and an onboard TI Tiva C connected 120MHz ARM microcontroller (with semi-custom program flash over ethernet). Both of our 9" tubes are stuffed to capacity, and partially rely on the straps to keep them close…

 

We’re just finishing our gripper that will be controlled by Hitec waterproof/IP67 servos, and still working out a pan/tilt camera system that will allow the cameras to sit in the domes. Pool testing has shown the ROV to be incredibly stable and much faster and maneuverable than anticipated. For videos and pictures of the ROV, you can check out the Facebook page (you don’t need an account to view it): https://www.facebook.com/UnderwaterRobotics/

I mostly just wanted to show it off, but the team and I would be happy to hear any comments or suggestions for improvements on our build! I’ve also attached the files for the dome add-on I made so the dome piece can held down with straps.



(Jacob) #2

Very well done, particularly on the pcb and fitting everything into such a tight package. It looks like a ton of work and TLC went into this.

-Jacob


(Christian Uhlenfeldt) #3

Great build, congratulations!


(Kevin) #4

Awesome job guys, I’m watching all the videos on your Facebook page. Some outstanding work there!


(Seth Opgenorth) #5

Update: We’re having all sorts of issues with the Hitec 5646-WP servos, and have had 3 of them die on us in the past two days. When they die, they work sporadically, and then start to get extremely warm. We’re only running them at 6.4V, which is certainly within spec (rated for 2 cell LiPo which is 7.4-8.4V), and give them a 5V signal (from a buffer IC). As a result, we’re going to be ditching the servos and going with a bilge pump with a decent gear ratio (somewhere around 16:1 to 64:1). In the team’s experience, the bilge pumps have been quite reliable (unlike the servos…).


(Rusty) #6

Seth,

Bummer. Those servos definitely don’t work well under full submersion. They are only rated to 1 meter depth and that seems to hold true.

I’m glad you can rig up an alternative!

-Rusty


(Seth Opgenorth) #7

Rusty,

We were having trouble getting them to work in the air! But, in defense, those servos were a few years old and have gone through who knows what…

The bilge pumps should work to much deeper depths. We’ll only need to go down to 40ft, and the shaft seals on them appear to be setup to work better under pressure (to a point, I’m sure…).


(Seth Opgenorth) #8

We got some more videos up on the Facebook page. Turns out we can do a barrel roll with the ROV and partially breach the surface of the water. Check it out here: https://www.facebook.com/UnderwaterRobotics/

 

We did have an unfortunate, mysterious event where 7 of our 8 motor controllers (Pololu G2, 18v17) failed while in the lab over the weekend. Still trying to figure out what could have caused the failure since things were quite stable electrically for quite a while. We run them at 13.8V (rated for a max of 30V), have large amounts of onboard capacitance, can only draw a max of 6A per driver when they’re rated for 17A continuous and we monitor them for temperature.