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Author Topic: Levellers  (Read 8322 times)

Turbulent

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Levellers
« on: March 17, 2009, 10:07:04 am »

Another Question!

Can Rc plane Gyros be fitted as levellers in subs?

Turbulent

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Heli Gyros as Levellers?
« Reply #1 on: March 17, 2009, 10:49:02 am »

I've found a supplier of Gyros built for Helicopters & Planes - Can these be used in Sub's
I cant see a reason why.

andrewh

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Re: Levellers
« Reply #2 on: March 17, 2009, 12:51:02 pm »

Turbulent

Theory says the answer is probably: 
I am assuming by "leveller" you are  speaking of the climb-and-dive plane

Gyros know NOTHING of level, or where they are or indeed, anything - they only know if they are being accelerated in rotation.
So the heading gyro on a heli is designed to hold the yaw heading (expensive ones have another channel which can adjust "gain" in the air) . 
Helis have a (potential) rate of rotation of maybe 10 per sec , so the servos are sensitive enough to nip this in the bud.  I would guess that a sub has a much slower potential rate of "porpoise" so the heli gyro may have trouble detecting the rate of rotation and fixing it

In summary - they are not levellers - they won't hold a level, but they might remove porpoising. 
They are also used on model planes/airships to hold the basic fuselage level  - so they have a good chance of being successful

There are btw model plane autopilots which will hold a trainer level in roll and pitch (and recover it if it deviates) these are optical and even out the light levels around the plane.  They MIGHT work very well underwater to hold a sub level :}
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXNA35&P=0

andrew

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Turbulent

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Re: Levellers
« Reply #3 on: March 17, 2009, 01:55:28 pm »

This is the one I'm looking at

http://cgi.ebay.co.uk/ESKY-RC-plane-model-parts-EK2-0704-Esky-Gyro-x1_W0QQitemZ270346427575QQihZ017QQcategoryZ19164QQtcZphotoQQcmdZViewItemQQ_trksidZp1713.m153.l1262


The plan is to fit it to the Aft planes & control the boat once dived, I will trim her on Ch6 on the front planes independently.

andrewh

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Re: Levellers
« Reply #4 on: March 17, 2009, 02:09:26 pm »

Good gwief!  Ive just seen the price!

Well worth a try - I see it has adjustable gain so you can use trial and error more trial to see what it needs
Don't forget it is a yaw gyro, so you need to fit it near the centre and aligned on the pitch axis (BYKT)

andrew
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Turbulent

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Re: Levellers
« Reply #5 on: March 17, 2009, 03:01:15 pm »

At that price it's worth a play - I've ordered one & will post how I get on.

Subculture

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Re: Levellers
« Reply #6 on: March 17, 2009, 04:48:06 pm »

No they don't work.

Turbulent

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Re: Levellers
« Reply #7 on: March 17, 2009, 09:28:12 pm »

Thats fairly definitive Andy, I take it you've tried!

Dave Merriman told me it was a stupid idea, so at least you were a little more tactfull!

andyn

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Re: Levellers
« Reply #8 on: March 17, 2009, 09:44:41 pm »

Esky gyros have faaaaarrrrrrrrr too much gyro drift, so your sub will probably end up vertical nose down %)

Worth a try though, probably best in a pool though.
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sheerline

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Re: Levellers
« Reply #9 on: March 17, 2009, 10:59:58 pm »

Hi Turb.
One thing i will say about levellers, they need to pretty responsive, the bigger the boat, the more sensitive and responsive they need to be. For example, on a small boat of say four feet in length, you need a responsive and undamped leveller to cope withit, you can toy with the sensitivity contol until you find a best, fits all, setting.
On larger boats these units have to very responsive indeed if they are to cope, another example is the huge Los Angeles clss sub, originally designed by the ingenious Dennis Cater of Eden Models. When I used that boat, it needed a self leveller so sensitive that it was virtually twitching all the time, if you so much as tapped the sub it would respond quite vigorously and aggressively with big inputs to the control surfaces.
The longer the sub, the more sensitive it needs be. There is a lot of inertia in a big sub and it needs a big input to correct even a small change in pitch whereas with a much shorter sub the movements can be slight and a bit slower... but they do have to be pretty responsive, I have little or no experience with aircraft gyros but I believe they are damped somewhat since aircraft are obviously lightweight and do not have a mass and inertia problem such as that found with subs.
It will be interesting to find out hoew you get on with this experiment. Good luck.
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Turbulent

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Re: Levellers
« Reply #10 on: March 18, 2009, 09:29:27 am »

I've got one ordered & I'll try it out on  Vanguard she's over 5ft & I agree that the bigger boats need them.

My Ohio was a very tricky boat to keep level & in the end I had one of Mike's levellers set as delicate as possible to overcome the inherent porpoising problem - I also found that fitting it in the bow section was more successful than the stern.
TheT boat was much better, the leveller looked after the stern planes & I trim her on the Fore' planes on Ch6.
However most of the Akulas I've seen are very stable, as was my Alpha  - even without a Leveller, my old chap hasn't even bothered with one in his & he sails it straight & level all the time.

The key to getting the most from any leveller seems to be to help it by not racing around at a scale speed of about 60 knots!

Mankster

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Re: Levellers
« Reply #11 on: March 18, 2009, 10:11:50 am »

Far more important than the length is the inherent dynamic stability of the boat and its speed is far more important. For example the old Sheerline Traf that needed a a pitch controller but didn't need one once the battery was placed below the WTC, my little Subdog which is still difficult to control even with the gain turned way up, and my 70" Typhoon which sailed serenely for most of the day even after the rear dive plane servo packed up.

Turbulent

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Re: Levellers
« Reply #12 on: March 18, 2009, 10:36:12 am »

Totally agree - it's all about speed / hydronamics.

I found that even my Type VIIs - The Robbe one & the OTW @ nearly 7 feet & my Tallyho, sailed really steady at low (Scale) speeds, these older boats need to really crawl - props just turning to reduce the lift generated at the bow & the drag coming from the clutter on the deck & the conning tower.

You're right about the Trafalgar, the difference in moving the batteries was unbelievble, mine was almost to easy to sail & would easily sail hands free for long runs, even turning at PD was easy, however before the battery was moved it would do the same as WWII boats & tend to lift at the bow.

Intersetingly, I wonder if all plane flyers fit gyros to all planes, afterall a trainer / high wing is far more stable than say a fighter.

Another point that was made to me by "someone in the know" whilst I was sailing the other week was regarding air pockets under the casing. This is a problem suffered by all subs & is overcome by general diving under power deeper than required & returning to trim at the desired depth, static diving /  surfacing is basically a myth & rarely if ever occurs.

Subculture

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Re: Levellers
« Reply #13 on: March 18, 2009, 12:17:10 pm »

I've never seen a gyro fitted to an aeroplane, helicopters yes, but not aeroplanes.

The vanguard should handle better than an Ohio- larger control surfaces. I read an article oncr that claimed the fullsize version was classed as aquabatic. Bit difficult to believe for a missile boat, but I would expect it to outclass any other Navy's in agility.

Turbulent

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Re: Levellers
« Reply #14 on: March 18, 2009, 01:56:27 pm »

You got a pm

microgyros

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Re: Levellers
« Reply #15 on: March 18, 2009, 06:13:29 pm »

---
My Ohio was a very tricky boat to keep level & in the end I had one of Mike's levellers set as delicate as possible to overcome the inherent porpoising problem - I also found that fitting it in the bow section was more successful than the stern.
TheT boat was much better, the leveller looked after the stern planes & I trim her on the Fore' planes on Ch6.
---
That leveller http://homepage.ntlworld.com/microgyros/ast.pdf is a model submarine device - just in case folk think there is a aircraft gyro that actually works in subs.

Feedback around the time of Paul Cook's Marine Modelling article (April 93?) http://www.modelboatmayhem.co.uk/Modellers/Paul%20Cook/1ndex.htm on his Type IX U-boat article  clearly indicated those levellerswere a vast improvement on sub levellers with a fluid type sensor(remember those) so I'm not holding my breath on an aircraft gyro which senses movement and not pitch angle.Ask any AMS old timer to relate their tales of trying aircraft gyros.

A gyro stabiliser won't even keep an aircraft level.Futaba had an autopilot to do thathttp://manuals.hobbico.com/fut/pa2-manual.pdf
It won't work in a sub either(or on a plane when it snows).

On the usefuleness of sub levellers in a small model,Paul's converted Academy kit is 18" long.
mike
 
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Turbulent

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Re: Levellers
« Reply #16 on: March 18, 2009, 10:19:09 pm »

That's the one I had in the Ohio & the T Boat - are you still selling them Mike?

dreadnought72

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Re: Levellers
« Reply #17 on: March 18, 2009, 10:22:58 pm »

...an aircraft gyro which senses movement and not pitch angle.

Hmmm. Could you not use a PIC chip or similar to integrate the pitch changes over short time spans in order to generate a pitch angle? Or do they drift too much?

Andy
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Turbulent

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Re: Levellers
« Reply #18 on: March 18, 2009, 10:29:11 pm »

...an aircraft gyro which senses movement and not pitch angle.

Hmmm. Could you not use a PIC chip or similar to integrate the pitch changes over short time spans in order to generate a pitch angle? Or do they drift too much?

Andy

What?!!!

andyn

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Re: Levellers
« Reply #19 on: March 18, 2009, 10:37:49 pm »

I think a pic chip would drift, but you would still need something to attach to it, such as a piezo or simalar such artical, remember, the pic is just the thin that makes stuff work.

Turbulent - PIC is a family of Harvard architecture microcontrollers made by Microchip Technology, derived from the PIC1640 originally developed by General Instrument's Microelectronics Division. The name PIC initially referred to "Peripheral Interface Controller". PICs are popular with developers and hobbyists alike due to their low cost, wide availability, large user base, extensive collection of application notes, availability of low cost or free development tools, and serial programming (and re-programming with flash memory) capability. ;)
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microgyros

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Re: Levellers
« Reply #20 on: March 19, 2009, 01:24:00 am »

That's the one I had in the Ohio & the T Boat - are you still selling them Mike?
Sorry,haven't made AST's for years.
I registered old domain names and posted the instructions online after an earlier post on Mayhem regarding speed controller setup.
mike
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Subculture

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Re: Levellers
« Reply #21 on: March 19, 2009, 08:25:35 am »

Most of the levellers I've seen use a PIC or Atmel microcontroller connected with an accelerometer usually set to 2g (g standing for gravity). These either use a miniature micro machined beam (like the Analogue Devices ADXL202) in the case of the Subtech leveller, or a small bubble of hot air which is sensed, in the case of the chips produced by Memsic, the latter are used by Norbert Bruggen in his LR2 leveller, and most other German makes of leveller/depth controller i.e.Rieger, Feldmann. I believe Mike was using these chips in his later run of levellers?

Mike's were always the best- simple to set-up, reversible and compact.

flashtwo

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Re: Levellers
« Reply #22 on: March 19, 2009, 08:50:09 am »

Hi,

There are some devices available from Technobots for measuring angle with respect to the earth's gravity - see   http://www.technobots.co.uk/acatalog/Accelerometers.html    and the associated data sheet show some calculations regarding signal value v. angle.

Also, at Active robots    http://www.active-robots.com/products/sensors/sparkfun/acclerometers.shtml    there are some other devices based on the same Analogue Devices chip.

Obviously additonal circuits will be needed to interface with the sub's control surfaces, but I suspect these could be found on Robotics hobby type websites.

Ian.
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dreadnought72

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Re: Levellers
« Reply #23 on: March 19, 2009, 09:11:03 am »

...an aircraft gyro which senses movement and not pitch angle.

Hmmm. Could you not use a PIC chip or similar to integrate the pitch changes over short time spans in order to generate a pitch angle? Or do they drift too much?

Andy

What?!!!
Ok ... what I mean is:

If the aircraft gyro senses movement, then every "timeperiod" it's going to produce an output which represents the change in angle during that timeperiod. For example:

0 0 0 0 0 0 0 -1 -1 -2 -1 -1 0 0 0 0 0 1 1 2 1 1 0 0 0 0 0 ... etc

By feeding this info into a program running on a microprocessor, you could integrate the changes in pitch into the actual pitch (just add the changes up), when the front planes are moved:

0 0 0 0 0 0 0 -1 -2 -4 -5 -6 -6 -6 -6 -6 -6 -5 -4 -2 -1 0 0 0 0 0 ... etc (here the boat's could be surface running, the forward planes move to dive, the boat dives, and then levels out)

Meanwhile, if there's no input on the front planes, and yet there's changes in pitch, then the boat needs to be levelled. In this case, a "not 0" in the first sequence should be met by a corresponding movement of the aft planes.

Maybe?

Andy
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Subculture

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Re: Levellers
« Reply #24 on: March 19, 2009, 09:42:17 am »

A chap called Andy Shaw built a submarine leveller, depth controller and ballast controller all into one unit called Neptune. It uses a PIC microcontroller, and he has the source code and other details on his webpage-

http://www.gloomy-place.net/neptune2src.htm

It's showing it's age now, as it uses a fluid sensor instead of the superior solid state accelerometers, however the code and hardware could be adpated I think if you're experimentally inclined.

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