AUV Project

A spot for our autonomous cousins.
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BrIDo
Posts: 3
Joined: Nov 22nd, 2010, 6:56 pm

AUV Project

Post by BrIDo »

Alright chaps,

Well done Steve on the website, some really good information on there.

I have a bit of a project on the go which has to be finished by April. We've set our sights quite high considering the lack of experience we have, but there are 5 of us working on it so hopefully we'll get there.

Quick overview of the project:
Our project is a model AUV - Automated Underwater Vehicle, for which the ultimate goal (in industry) is a vehicle capable of navigating to a predesignated area and performing some task (i.e. actuate a valve on a horizontal christmas tree). The image recognition capabilities on the more advanced models using cutting edge software, and given we have a budget of £500, we're going to be downsizing quite a bit. The emphasis of our project is stability, which we are investigating on two fronts. The first is an efficient hull design, to minimize drag force due to underwater currents. The second is by way of a stability system using a feedback system - which I am working on. Ideally the AUV would navigate a predetermined path and then when it reached it's 'destination' it would try it's best to stay in that position.

We're currently detailing the hull design, I'll get some photos up tomorrow.

Our current set up is looking like this at the moment:
- 6 x 12v DC motors (taken from Rule 500 Bilge Pumps).
- Craft dimensions approx. 650 x 450 x 20mm
- Solid steel skeleton structure with steel/aluminium sheeting.
- PicAxe / Arduino Controller with IMU
- Neutrally buoyant

Quick question for Steve, what sort of mass have your ROV's been? The reason I ask, our craft is likely to displace 40kg worth of water and so we'll need to add a decent amount of weight to it. Seeing as you've often opted for the converted bilge pumps as thrusters, do you reckon they'll provide enough thrust to actuate our AUV? We're planning to have some of the thrusters in ducts, which I'm reconsidering as I think we'll restrict fluid flow too much.

Also - when comparing different bilge motor cartridges (of the Rule variety), was there much difference in physical size between say, the cartridges in the 500 and the 750?

Cheers.
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sthone
Posts: 588
Joined: Nov 8th, 2010, 9:25 pm
Location: Connecticut
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Re: AUV Project

Post by sthone »

I really don't know what the mass of my Rov's have been or how much they displace. (I'm not really good at doing all those kinds of calculations :oops:) The overall dimension of my Seafox are L=14 x W=14 x H=10? and I think it weights about 14lbs. I tend to just build them so they float then add just enough weight to get them to the desired buoyancy.

The Rule Pumps I use put out about 2lbs of thrust each and the Mayfair ones I have tested put out 1.8lbs. I haven't actually compared the different models against each other. (such as the Mayfair 750's vs 500's) I usually go with the 750's because the price isn't that much difference over the 500's but they are more powerful. I'm pretty sure the pumps are the same physical size but they just use different size motors.

I haven't tried a full duct yet, a lot is going to depend on the design of the ducts. I have played around with some kort nozzle designs though, sometimes I get the same thrust but with less amp draw and sometimes I do get a bit more thrust but these where all just homemade nozzles out of PCV.

-Steve
BrIDo
Posts: 3
Joined: Nov 22nd, 2010, 6:56 pm

Re: AUV Project

Post by BrIDo »

Well, to be fair it's a bit more difficult to work out for the ROV's given the shape of them. Our AUV has a 'skin' on the outer surface and will be waterproof, so it makes it easier to work out it's volume. It will displace about 40 kilos of water. So basically, we need 40 kilos of mass to get it neutrally buoyant.

Regarding the pumps and motors, the reason I ask about size is because we're drawing up motor mounts and it would be handy to know if 'one size would fit all', so to speak.

Aye, I had a look at the optimum duct length, but most of the ducted propulsion I've seen uses varying shapes and serves to increase efficiency in one direction only - and so for bidirectional thrusters are maybe not the best option. I found these thrusters the other day:

http://www.tsltechnology.com/marine/thrusters_data.htm

I enquired about the price, £1000 a piece!
BrIDo
Posts: 3
Joined: Nov 22nd, 2010, 6:56 pm

Re: AUV Project

Post by BrIDo »

3D model of how it will look is shown:

http://d.imagehost.org/view/0285/skinned
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