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Author Topic: AUV project design: brainstorming  (Read 4761 times)

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Offline skatjTopic starter

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AUV project design: brainstorming
« on: April 05, 2008, 12:12:18 AM »
I'm thinking of constructing an AUV as an engineering project. I will be interning with an underwater robotics lab at a local university that designs their own AUVs so I want to be able to apply what I learn from that experience.

Some of the main themes/design goals I have been thinking about are
- Energy autonomy (hopefully the ability to remain underwater/at sea indefinitely)
- Small size (3-4 ft long)
- Macroscopic navigation (I heard this was a problem for AUVs, havent done the research though)
- Hydrodynamic stability
- Cost (duh)

Can you guys think of some rough brainstormed solutions for these problems? I haven't done the research on feasibility/whether it has already been done, but I've been thinking about:

- A retractable pod that floats to the surface, has a GPS receiver and solar panels to recharge batteries during the day. AUV releases this pod every so often to calculate position deltas and direction of travel (while underwater and "blind", itll be trying to estimate where its going)
- Some kind of built in water wheel that will spin and drive a generator as the AUV moves through the water? So as it is expending energy to move it is also gaining some back (no idea if this is even possible/feasible)
- Using a cell phone as a GPS/wireless communication would also be pretty neat, although I'm not sure how difficult this would be

Can anyone suggest major problems with current AUV design that I could maybe try and design a solution for, or maybe ideas for possible solutions to my current problems? (or any ideas that you feel would be cool to include in an AUV design)

Thanks!
« Last Edit: April 05, 2008, 12:15:25 AM by skatj »

Offline dunk

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Re: AUV project design: brainstorming
« Reply #1 on: April 06, 2008, 06:10:52 AM »
i've put some thought into this.
i intend to build an ocean going bot one day but don't plan to start any time soon.

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- Energy autonomy (hopefully the ability to remain underwater/at sea indefinitely)

navigation buoys use 2 main methods of power generation: solar power and an Oscillating Water Column.
the problem with both these methods on an AUV is that it is under water.
water blocks so much of the suns power that solar power is far less effective so the closer you are to the surface the better able you are to recharge.
the other method, an Oscillating Water Column, needs to be sitting on the surface where the waves are to bob about to generate power.
surfacing to generate power is fine in calm weather but when the whether is bad your ROV will get blown off course.

Quote
- Macroscopic navigation (I heard this was a problem for AUVs, haven't done the research though)

out in the open Ocean navigation is not really too important. there is no land to hit so as long as you are moving in the right general direction surfacing to get a GPS fix once every few days would be fine.
if you are close to land however navigation is far more important as you need to worry about running aground.
off a fairly blank coastline the tide will typically reach 1.5 knots, parallel to the coast at full flood.
if you are close to any sort of headland this will increase dramatically. (the spot where i learned navigation i had to contend with up to 8 knots of tide in a boat that wound average 4 knots.)
on the plus side, any effect of tide will reverse every 6 hours and run the opposite direction for approximately the same length of time so as long as you have not hit anything you will be back where you started 12 hours later.
without going into too much detail, coastal navigation of a AUV with limited power reserves (ie. low speed) would be very tricky.
ocean navigation would actually be far easier.
of course, if you are just going to chuck this in a swimming pool or non tidal body of water non of this is an issue.

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- Cost (duh)

so if you are going to let this loose in the sea you have to be prepared to loose it.
the sea is a hostile environment. there is no way you could predict everything that can go wrong.

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- A retractable pod that floats to the surface, has a GPS receiver and solar panels to recharge batteries during the day. AUV releases this pod every so often to calculate position deltas and direction of travel (while underwater and "blind", itll be trying to estimate where its going)

moving components increase the likelihood of failure.
far better to surface occasionally to take GPS readings.

Quote
- Some kind of built in water wheel that will spin and drive a generator as the AUV moves through the water? So as it is expending energy to move it is also gaining some back (no idea if this is even possible/feasible)

um. no. unless you can design a system more than 100% efficient it would slow the UAV down more than the power it would generate.
http://en.wikipedia.org/wiki/Perpetual_motion

Quote
- Using a cell phone as a GPS/wireless communication would also be pretty neat, although I'm not sure how difficult this would be

so it is very feasible close to land but if you intend to go far off shore you will have no reception.
satellite phones are an option but very expensive.

try searching for the phrase "Slocum glider" for an insight into how marine researchers have tackled the problem.


dunk.

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Re: AUV project design: brainstorming
« Reply #2 on: April 06, 2008, 04:34:22 PM »
search the forum for submarine and read the posts that have 'submarine' highlighted in yellow. Interesting/useful reads to help you out and get you thinking.

Quote
Quote
- Some kind of built in water wheel that will spin and drive a generator as the AUV moves through the water? So as it is expending energy to move it is also gaining some back (no idea if this is even possible/feasible)

um. no. unless you can design a system more than 100% efficient it would slow the UAV down more than the power it would generate.
http://en.wikipedia.org/wiki/Perpetual_motion

lol . . . look up something called a 'glider' . . . thats the most power efficient robot sub design possible.

Offline skatjTopic starter

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Re: AUV project design: brainstorming
« Reply #3 on: April 07, 2008, 01:50:31 AM »
Btw, what's a rough price quote for a 3-4 ft long AUV with minimal functionality?

This is for a science & engineering competition, so if it's over a 1,000$ I may just work on the retractable pod portion as a prototype.

Offline JonHylands

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Re: AUV project design: brainstorming
« Reply #4 on: April 07, 2008, 07:10:51 AM »
You mean to buy a commercial AUV?

The cheapest one I'm aware of starts at a baseline price of around $25,000...

- Jon

Offline skatjTopic starter

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Re: AUV project design: brainstorming
« Reply #5 on: April 07, 2008, 11:59:16 AM »
I mean build one

Offline JonHylands

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Re: AUV project design: brainstorming
« Reply #6 on: April 07, 2008, 01:02:37 PM »
If you're going to build it, and you're not looking to go deep (say 10m max), and you already have a metal lathe to machine end caps, and you're willing to stick with hobby-level parts, and go fairly skimpy with sensors, you might build one for under $1000...

To build MicroSeeker, I would have to spend probably closer to $2000, with probably 2/3 of that going to the electronics/sensor package.

http://www.huv.com/uSeeker

- Jon

Offline Lefteris

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Re: AUV project design: brainstorming
« Reply #7 on: April 07, 2008, 01:47:29 PM »
You might find help for UAV's here.

It has instructions for building UAVs for budgets from 500$ to 1500$.

Hope it helps

EDIT: Sorry ... read the word wrong .... you don't want UAV , you want AUV ... my bad  :-X
« Last Edit: April 07, 2008, 01:50:03 PM by Lefteris »

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Re: AUV project design: brainstorming
« Reply #8 on: April 07, 2008, 02:34:12 PM »


Quote
Sorry ... read the word wrong .... you don't want UAV , you want AUV ... my bad
yea I confused the two often as well

Quote
If you're going to build it, and you're not looking to go deep (say 10m max), and you already have a metal lathe to machine end caps, and you're willing to stick with hobby-level parts, and go fairly skimpy with sensors, you might build one for under $1000...
My robot fish is about $600 in parts . . . but it took 3 years in labor/research, plus I have access to expensive equipment . . .

You can dramatically lower the cost a lot of you remove the 'autonomous' part, and make it tethered. You could always upgrade it later as you become more experienced and get a larger budget. Like $200 perhaps.

Offline skatjTopic starter

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Re: AUV project design: brainstorming
« Reply #9 on: April 07, 2008, 08:08:20 PM »
I'm thinking more along the lines of an underwater observation station that anchors itself to the seafloor and moves every so often (by texting GPS coordinates), because I think underwater gliding is a little out of my league and the ability to remain stationary for large periods of time make achieving energy autonomy  a lot easier.

After some more brainstorming, I've revised my goals a little bit
- Mobile Underwater Observation Station
- Tethered buoy with a cell phone (will only operate this on the coasts) with GPS, and solar panels

This just caught my eye: http://www.stirlingengine.com/ecommerce/product.tcl?product_id=78
I was thinking I could attach a temperature sensor so when the computer detects a large enough temperature difference it'll start the wheel mechanically, and let it spin a generator. (this will be in addition to solar power)

Feasible or am I missing something huge? It is a bit pricey so I want some opinions before researching it further. Would it run on warm seawater, considering it runs off a warm hand.

Offline airman00

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Re: AUV project design: brainstorming
« Reply #10 on: April 07, 2008, 08:17:36 PM »
also look into Peltier Junctions for heat to electricity conversion

btw , the amount of energy created is minimal
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

Offline skatjTopic starter

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Re: AUV project design: brainstorming
« Reply #11 on: April 07, 2008, 10:20:09 PM »
^yea I looked it up on Wikipedia and it says it outputs less than a watt, so that's off the drawing board

Offline airman00

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Re: AUV project design: brainstorming
« Reply #12 on: April 09, 2008, 09:30:37 PM »
^yea I looked it up on Wikipedia and it says it outputs less than a watt, so that's off the drawing board

why not have it rise to the surface and put solar panels on it?
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

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Re: AUV project design: brainstorming
« Reply #13 on: April 12, 2008, 06:46:45 AM »
Quote
While the MM-7 operates based on well understood physics, it may be the closest thing to magic and a perpetual motion machine you can buy anywhere at any price.
lol, snake oil for sure!

Actually, it works on thermal gradiants - doesn't matter how 'warm' it is.

Anyway, if you have something already floating on the surface, just put a solar panel on it as airman00 said and tether the power cable.

Offline skatjTopic starter

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Re: AUV project design: brainstorming
« Reply #14 on: April 14, 2008, 12:56:25 AM »
Yea, that was my original idea, I;ll stick with it  :)

Offline Asellith

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Re: AUV project design: brainstorming
« Reply #15 on: April 14, 2008, 04:57:20 PM »
Could put an accelerometer on top and use it to watch for storms. If the seas get to rough you can pull in your tether and go into a sleep mode to try and conserve power till the storms move on. check sparkfun for cellphone parts. They use the telit module but you can get a module with rs-232 and power adapter for less from another company. I have the addy at work so if your interested I can post it tomorrow
Jonathan Bowen
CorSec Engineering
www.corseceng.com

 


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