question about depth control

[raalst]

[color=#000000]Hi all,

I am currently dabbling in control theory and I was
wondering ]



Edited By raalst on 1093174218

[Guest]

Depth controllers work on the

Depth controllers work on the forward hydrovanes.

It's pitch controllers that work on the rear hydrovanes.

Andy

[anonymous]

You raise an interesting point

You raise an interesting point because a lot of level controllers are electronically linked to speed controllers anyway to prevent things going haywire when you go astern.

The reason not to use a "speed" signal is probably the usual design compromise. In the same way, I think that using forward AND stern hydroplanes adds a lot of mechanical complexity and extra push rod seals.

Andy's comment is interesting too and that is the convention isn't it? Is that because stern planes are usually further from the centre of buoyancy ie have a bigger turning force? (Sorry not to look it up but I'm missing all my books - moving house!)


My Webpage

[Guest]

I think it's more to

I think it's more to do with the way rear and front hydrovanes work. This is my theory, as I have observed, which may or may not be correct.

When you dive with rear hydrovanes only, the boat dives in an arc, first going up a little before submerging. As depth controllers work by sensing pressure, this would confuse the controller into thinking the boat was doing the opposite of what was commanded.

Forward hydrovanes basically submerge the boat in a 'flat' fashion. There is very little evidence of the boat pitching about it's axis to submerge. Therefore a tilt sensor, as used in the angle keepers would have little effect.

Interestingly, I read on Norbert Bruggens site that he is developing a special leveller for forward hydrovane use for his Delta kit. This boat of course, has no rear hydrovanes.

Andy

[anonymous]

Yes - I have seen

Yes - I have seen the "up and over" explanation of stern dive planes but I think it is more apparent than real.

You see the stern come up and it breaks the surface and it looks as if the whole submarine is brought upwards. But in fact it is just that the stern planes have more "leverage" on the angle of the submarine.

I think that you could use stern or bow planes fpr depth and/or level control. It is just that stern planes are more effective for level control.

BTW Andy I agree with your "struggle" elsewhere abiout failsafe delays. I had to insert a delay in my speed controller last year because just as I was diving the speed controller would lose signal and go to low output!


My Webpage

[Guest]

Hmm. Interesting. The forward hydrovanes

Hmm. Interesting. The forward hydrovanes are generally close to the boats C.O.G, therefore a smaller moment of force will act on the boat, unless the vanes are correspondingly larger in surface area to compensate, so that would be a good point.

Does your R-Class have working forward hydrovanes?

If so how about testing your theory, as I haven't a working boat with forward hydrovanes.

Andy

[anonymous]

Unfortunately not - I just

Unfortunately not - I just keep them folded up - for simplicity again.

I think the theory is right though. The sub is designed and ballasted so that the fin and periscopes are at the centre of buoyancy/centre of gravity - that is where you need the depth control!

Forces from hydrovanes act around this and the turning effect is increased with the distance from the fin or sail.

An additional effect is that once the sub is inclined to the direction of motion , the sub hull itself will also produce a substantial force.

Presumably the several classes of US subs with sail mounted planes were designed this way for accurate depth control. (Sail mounted plane will give minimal turning effect.)

Would any one like to comment on this?



My Webpage

[JWLaRue]

Some food for thought.....

Skip Asay

Some food for thought.....

Skip Asay runs his Albacore with both pitch controller and depth controller connected to the stern planes. It behaves quite nicely with that configuration!

-Jeff