Computational Buoyancy Control

Clint Power

Hey guys,

I'm a final year engineering student and I've just finished a project on developing a neutral buoyancy controller. It involved mathematically modelling the buoyancy and making a prototype that neutralises itself at a depth set by the diver.

The project's just about finished now, but I'm just wondering what actual divers would make of it. Basically, would you ever trust a computer to control your compensator?

I have a feeling it's gonna be a resounding "no", and that's completely fine. I just think some divers' opinions might make for a nice qualitative section of the discussion, since it's currently based all on numbers.

So if you have a spare minute, I'd really appreciate it if you could just let me know how you'd feel about such a device and give an indication of your diving skill level. Thanks a million!

locum-motion

No, I don't think I'd like it. If I want to descend from 20 to 21m, or if I want to start slowly multi-levelling up towards the end of my dive, I like to just be able to do it and adjust my own bouyancy as required. I don't think I'd like to have to tell my dive computer "OK, I'm going down now."

Would it have possible applications in bouys used in weather/wave/current detecting technology, or tsunami warning systems?

From an engineering point of view, though, I'm sure it must be an interesting project.

Good luck,
L-M,
PADI Divemaster
450ish dives
8+ years

Clint Power

Thanks for the reply. Yeah, it made for a pretty interesting year. The whole thing is quite widely adaptable, scuba is just where the initial proposal came from. Since I've never dived myself (planning to now though), I just had to rely on the information I was given.

I believe buoyancy control can be fairly tricky to grasp for a new diver, so do you think it could be of any advantage at beginners' lessons in a pool or something of the sort?

locum-motion

It can be a little tricky at first, but becomes second nature quite quickly. I'd imagine that process would be slowed down, though, if you had a gadget to do it for you when you started. Then you'd be less likely to learn how to do it right.

Clint Power

Good point, I'll take it on board. Thanks a million for the feedback.

longshanks

When I breathe in I rise a little bit, when I breathe out I sink a little. Would the computer be continually adjusting to my breathing pattern?
Also, everything locum said.

Catmologen

Sounds like a fascinating idea OP, i would love to read some more about it have you got a website or anything?

It could have applications disabled divers perhaps. Also maybe as a safety device to prevent divers from breaking decompression ceilings etc. Although there would have to be some kind of a manual override in place.

Clint Power

longshanks wrote: »

When I breathe in I rise a little bit, when I breathe out I sink a little. Would the computer be continually adjusting to my breathing pattern?

The current programme is fitted with a "dead-zone" that gives the operator control over their buoyancy tolerance. So, for example if you were neutral at 20m and set your dead zone to 5%, you would have a margin of 1m (up or down) in which the controller would do nothing. This is to account for changes in buoyancy by respiration.

I'm not sure if they're reasonable values in reality but hopefully that answers your question.

Catmologen wrote: »

Sounds like a fascinating idea OP, i would love to read some more about it have you got a website or anything?

It could have applications disabled divers perhaps. Also maybe as a safety device to prevent divers from breaking decompression ceilings etc. Although there would have to be some kind of a manual override in place.

There's no website I'm afraid as it's just a student project and it's a far cry from actually existing as a product. I'll be compiling the report over the next couple of weeks though, so I'd be happy to send you a brief "best of" if you're interested. Just to warn you though, it favours on the side of maths and theory as opposed to the actual application of it.

As you said, it could definitely be used for disabled divers. Also decompression ceilings, along with runaway buoyancy, were part of the original project scope. The current device doesn't have an override as it's small scale and not for diver use, but to the best of my knowledge, including an override on a larger scaled device shouldn't be a problem. It's actually one of the recommendations should any of next year's students take this project further.

loctite

I actually think that this is a great idea.
Maybe not so much as a buoyancy controller but a fail safe device.
Like the other posters have posted buoyancy control is a tough skill to master but it is essential to diving. However you could have a tolerance set far higher so that the device could detect a ascent rate that was too fast and would automatically slow the diver down maybe in the case of a runaway ascent. I think that that could have some application especially for schools or newer divers.

If would have to allow for divers to make "safe" mistakes and yet not allow uncontrollable ascents.

To qualify that though you would need to consider an out of air situation and the fact that a diver trying to reach the surface could potentially be slowed down by your device with fatal consequences. And before someone even mentions that you shouldn't be ascending any faster than the recommended 18m/ min or some other algorithm equivalent.... get real.

Could have applications on teaching drysuit diving too.

Instructor 13 years
one or two dives under my belt.

should have read your previous post more carefully, you have already considered an over ride.....

seadeuce

Have you considered rebreather diving as your target (market)?

With rebreathers respiration does not affect buoyancy as it does in scuba due to the counterlung.

Or does that upset your maths? :-))


Seadeuce

loctite

seadeuce wrote: »

Have you considered rebreather diving as your target (market)?

With rebreathers respiration does not affect buoyancy as it does in scuba due to the counterlung.

Or does that upset your maths? :-))


Seadeuce

I thought it did effect your buoyancy except in the opposite way no??

seadeuce

Have used the Drager rebreather.

On exhalation the countelung (located at your back) fills up, then empties on inhalation. Your buoyancy is not affected as with scuba and this will feel weird at first as you expect to fall/rise in the water column.

Just wondereing how this computational device would apply here.


Seadeuce

Clint Power

loctite wrote: »

However you could have a tolerance set far higher so that the device could detect a ascent rate that was too fast and would automatically slow the diver down maybe in the case of a runaway ascent. I think that that could have some application especially for schools or newer divers.

Interesting. So use the "dead-zone" function for a larger range of safe depth and the device as a back-up should they breach this? It's easily doable alright. Great recommendation!

seadeuce wrote: »

On exhalation the countelung (located at your back) fills up, then empties on inhalation. Your buoyancy is not affected as with scuba and this will feel weird at first as you expect to fall/rise in the water column.

Just wondereing how this computational device would apply here.

It would depend on how you tune it. If you give yourself a large enough "dead-zone" margin it wouldn't do anything for relatively small changes in depth due to breathing. Without the margin, it would constantly try and compensate for these changes, but during testing, this just proved to be a waste of air.

As for the maths, the respiration and buoyancy are modelled separately so both are interchangeable. The effect of breathing acts as an external (positive or negative) force on the neutral buoyancy model and then the model behaves as a result if this. So the respiration details can be changed without upsetting the overall model.

elcowboyspace

This really does sound like quite an interesting idea you have there. The applications for diving are fantastic. Granted, as has been mentioned already, an override in my honest opinion ( NO IMHO here ) is an absolute must. Needs a shutdown function, and an easily accessible one at that for sure before any diver would really consider using it. The "dead zone" adjustable tolerance is a nice/essential feature. Again as mentioned already buoyancy is something that comes after practice and plenty of diving and computer control of the set level is only one part of it, I dont think this computer controller is going to take into account body positioning in the water. horizontal, vertical or somewhere in the middle, The difference between horizontal and vertical in a wing and dry suit can definitely mean neutral or positively buoyant, a change which is autonomously dealt with by most divers of any experience. Inclusive of all thats been said above though I would really like to try this system out if it became feasible to produce in the real world as opposed to purely mathematical. It may work, it may not but would be very interesting to experiment with under controlled/safe conditions.

Divemaster /dive leader 7 years.... and happy at that "professional" level.