flying uav update - not good

BeanieBots

Moderator
I couldn't agree more Tom2000 but the project is non starter without each aspect fully covered.
While the fibreglass for the hull is curing, the auto pilot can be tested on a buggy in the carpark without the need to worry about salt water probelms or 3D compasses. Those can then be added in once the fundamental control mechanism has been determined. Maybe it IS possible to control with ONLY GPS data. A test would prove that one way or the other irrespective of anything said in theory.
"Controlled" sea conditions (I'm refering to pitch & roll) could be done on the bench to see if the control system can cope. IMHO, all this needs to be done early on to determine what sensors are required and then how they will be fitted & powered and that would then determine many of the hull requirements which would then present which of the previously discussed issues need to be resolved regarding through hull fitments etc.
Power weight ratio for example will be just as much a hull dimension criteria as any of the other topics covered. No point having a hull too small to hold a battery large enough to power one LED for 10 seconds and no point having one so large that it requires batteries that are cost prohibative.
Talking of which, we still don't have a figure for budget.
Maybe the budget could stretch to a fishing trawler complete with deisel engine for power?
At the moment, it's all just speculation.
Probably beyond the 08, I agree. Maybe a uFPU or two.
 

Tom2000

Senior Member
...a fishing trawler complete with deisel engine for power?...
Hmmm.... the difference between a 30 day crossing and a six month crossing.... something to consider. (Not a full-sized trawler, but internal combustion power...)

Also an idea not to be thrown out with the bathwater is a planing hull (which I initially considered, but discarded because of the complexity of the control system.) Maybe that should be back on the table, too.

(By the way... before anyone asks why I didn't propose a catamaran, it's because of their propensity to pitchpole. But a powered cat wouldn't have that problem. Maybe something else to consider.)

Tom
 

Brietech

Senior Member
Is it not possible to seal electric motors effectively (so only the prop protrudes)? I was under the impression that that problem had been fairly solved by all of the RC boat (and warship) people.
 

papaof2

Senior Member
I think one consideration in sealing the ship to keep water away from the electric motor is the amount of time the motor is expected to be running. If the through-hull shaft of a combat ship has packing of some type to prevent leakage, it is probably checked before and/or after each run. How much wear would the packing experience in 30 days of continuous running?

One possible "no hole" drive configuration would be to have a flat vertical surface near the stern of the ship that could have a motor-driven rare-earth magnet on the inside of the ship and the driveshaft/prop with a rare-earth magnet on the outside of the ship. I have no idea how much torque could be transferred in this manner, or what method would be needed to attach the outside magnet to the shaft driving the prop (considering the unfriendly environment) - although the Roomba vacuum appears to use a non-contact drive system for one of the "fans" (still disassembling a non-working unit acquired very cheaply on Ebay)..

John
 

demonicpicaxeguy

Senior Member
ok, an update on things so far :

not suprising the money i'm going to put towards this is delayed... again...
the budget when i do get my money is $4000

ladies and gentleman an important lesson in buisness don't hand over somthing until the cheque clears! no matter how credible the customer!

navigation - going to the markets tomorrow see what i can find there

comunication - mobile phone on a cheap plan with global roaming plus a decent external ariel

powersupply - the sheer area require to get 200watt out of it is a little excessive considering the weight and usable sunlight so wind power is going to be the main source of power it will still have a couple of solar panels but that will just really be for keeping the navigation stuff going in the worst case of no wind for several days

hull design - while i still want to look at the battle ships and i'm going to get along to the meeting the "sydney battle squadron" has , my son is quite interested in it now,
anyway i'm looking at a torpedo style thing with a dome at one end and a weighted rear end that stays a little deeper into the water i have a 375mm diameter pvc pipe up the side of the house which would be perfect for the job a simple "T" piece with a dome on one end and a cap on the other near the front to mount the wind generator on would be perfect and i'll have to put in a weighted keel which won't be hard to do


cargo hold - i'm thinkiing it could be usefull ... just a thought,

the packing for the propeller shaft is somthing i didn't think much of i've got to admit i was thinking of somekinf of nylon seal but if there is a better solution...

i thought the gps units had compasses built in to them and they spat out directional data in the nmea strings, or is that some gps units and not others
 

Tom2000

Senior Member
i thought the gps units had compasses built in to them and they spat out directional data in the nmea strings, or is that some gps units and not others
They do, but the information from a GPS is course made good, not heading. Course made good is what you need for gross navigation, but isn't sufficient, by itself, to control a sailing craft. You also need heading information.

With a motorized craft, you might be able to get away without a compass.

By the way, here's some advice that you can use to help you through your project: "If at first you fail, try again. Fail better."

I don't remember who said it, nor whether I have the quotation exactly correct, but for folks like us, those are words to live by.

Good luck!

Tom
 
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andrew_qld

Senior Member
As Tom said, GPS won't give you the direction you are facing in unless you are moving. So if you are climbing 10 metre swells at full steam flat out going anywhere, poor old MV Picaxe will loose its way. You will need some sort of compass sensor.

If they can fly a plane accross the english channel with a person on board using only solar power (and that was in 1981) then surely a solar power boat is possible. Granted, the area you have available for solar cells is smaller but solar cells & batteries are far more efficient these days.

And I guess the thing needs some sort of a backup plan too. Like if the GPS dies for more than say a day, perhaps get it to head on a bearing for the nearest port (with cellphone coverage?). Better still two of everything for redundancy?
 

moxhamj

New Member
I wonder if it is worth building a simple boat and sailing it up a nice calm river like the Hawkesbury first - just to test out all the electronics and comms and headings. Then if that works take the working design and 'robustify' it. I think the electronics might turn out to be the easy bit but even that might be complex. I am still trying to get a working long term reliable radio link to go a few hundred metres. I have more and more admiration for NASA driving rovers round on Mars.

Seals are complex. I kind of like the idea of magnetic coupling as suggested by papaof2. But even a propellor can get fouled - there is probably a good reason fish are designed the way they are. I worry about wind - it is fine to have a wind turbine on a big stable container ship that can straddle several waves, but little SS Picaxe is going to be motoring up and down some big swells with salt water being blown into the turbine bearings - it is hard to see that surviving for very long. Everything that is exposed is going to need to be brass, stainless or UV resistant plastic. There are marine wind turbines available commercially but they are still designed to be on top of a mast out of the salt spray.

To start very simple - is it possible to have a picaxe with a GPS etc that can give a bearing indication and transmit it via a satellite phone to a remote location? That in itself would be quite an achievement.
 

Brietech

Senior Member
Interesting thought re: propulsion . . . Getting a propeller fouled up somehow (likely getting clogged with seaweed or something) seems like one of the biggest threats. What about using an above-deck fan as propulsion? Basically an "airboat" (http://en.wikipedia.org/wiki/Airboat). It's probably too inefficient, but it's a thought.
 

demonicpicaxeguy

Senior Member
propellar fouling is a somewhat easy one to solve, just use a non hooking propeller if you look at one from the back you'll see that in most cases that the main body of the blade actaully forms a crude kind of hook where as a non hooking one doesn't,

the other way to go would be a vertical centrifugal type or even a simple pump sucking water in through the front and jetting it out the back
 

moxhamj

New Member
Some back of an envelope calculations - if the boat sits substantially above the waterline then wind drag will be the primary force to overcome, and if it sits substantially under the water (eg a submarine with a periscope with solar/wind on the periscope) then water currents will be the primary driver. Both forces need to be overcome otherwise the boat will just drift along with the rubber duckies. Just roughly, a human can produce 100W of power continuously (up to 600-700W peak) and so if a boat is sort of human sized and human powered it should be able to cruise along regardless of currents. A canoe or a rowing skull shape is certainly the most efficient. A canoe with some lead at the bottom (lead acid battery?) so it is self righting, solar panels on top, largely sealed up but with a bilge pump and a prop at the back could be a simple solution - at least this is using readily available components. Testing could be done at a local Sydney beach - if it can survive being dumped under a wave it should survive most of the open ocean. Could be a good excuse to use the $4000 to spend a day at the beach...
 

demonicpicaxeguy

Senior Member
that was one of the reasons for choosing the pvc piping, it's actaully a section of pipe from a sydney water main generally these pipes can take quite a beating that would even give a canoe a good run for it's money

at the moment i'm looking at somthing that'll only be 6 odd feet long if that

as for the budget... i've got more faith in getting a few sponsors, the person who owes me the money has become uncontactable again so i my have to do this on the cheap which changes a few things
 

demonicpicaxeguy

Senior Member
just had a thought while browsing the atmel site and found the
ATR0635 basically a gps reciever in a chip if it's got a serial pin that puts out the nmea strings it might be a better option than a full blown gps unit
 

Wrenow

Senior Member
Is it not possible to seal electric motors effectively (so only the prop protrudes)? I was under the impression that that problem had been fairly solved by all of the RC boat (and warship) people.
Yep. Called stuffing tubes - same principle as used on ships and boats, but ours are simpler. There are discussions/plans/diagrams on the NTXBG.org web site and other places.

NTXBG was just at Maker Faire in Austin, where Servo Magazine and Nuts and Volts offered to share booth space with us.

We earned an Editor's Choice award!

There was an autonomous Benthic (lake bottom bottom) mapping vehicle there which uses GPS navigation and a BASIC Stamp (actually a couple, and a small PC). We discussed the Picaxe, and he is planning on looking into it for the next generation (he had not heard about the X1's and the price/features astounded him). Some pictures of the event, including the autonomous Benthic Mapper are here:http://picasaweb.google.com/wrenow/MakerFaire

Again, many of the issues I have seen mentioned have been solved by the AUSBG (Australian Battle Group at AUSBG.org) and others for Model Warship Combat. Those wanting to do this really should get to know their local Warship Combat club, as there is a lot of hardware that is readily usable or adaptable.

And, a 6 foot fiberglass combat hull is cheaper than a canoe, more stable, and may be better suited for this particular project.

Be aware that I have seen a large, heavy cruiser hull driven at about 2kph (kilometers per hour, not knots), direct drive, by 2 Tamiya Solar Motor 02's that draw about .25A at full stall. Geared for efficiency, they would probably be faster. This is nowhere near 100W.

Oh, got to meet the new owners of HVW - nice people. Bought a couple of gearhead motors off them - one is a 25:1 planetary gearhead and motor that is 6mm in diameter and about 1/2" long!

Cheers,

Wreno
 
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demonicpicaxeguy

Senior Member
very interesting method they used,

i was pondering on the idea that Tom2000 came up with, internal combustion ,
world circumnavitagtion won't be possible with it but with a correctly selected engine, and fuel storage it shouldn't be too hard to send it across a good part of the country


on the other hand Wrenow brings up the interesting point of the tamiya solar motors, with a smaller hull and a couple of solar panels with a small battery pack it could be interesting too
at several km/h it could travel some serious distance

watch this space - the gps should be here soon
 

Wrenow

Senior Member
We (the NTXBG) hit the Popular Science Blog! Woohoo!!! http://popsci.typepad.com/how20blog/2007/10/radio-controlle.html

The first photo is the Richelieu (not mine) as a "Visible Ship" display, with Reluctant and Greene (mine) in the background. The next is a photo of the gun system of my son's Dunkerque with the guns looming over my Lake Shore. The last is the drivetrain of the Dunkerque (Speed 400 motors with planetary gearboxes to add torque and efficiency).

Maker Faire was unreal. Check it out at http://makerfaire.com/
Lots of picaxable projects. :)
And, Solarobotics/HVW, one of the Picaxe distributors was there!

Cheers,

Wreno
 

Dippy

Moderator
That looks fantastic fun Wreno.

I'm not sure whether dpg's boat will need to be armed - unless it veers off course up the Persian Gulf. Or gets attacked by the Pigmy Pirates who operate in the Indian Ocean.
 

Wrenow

Senior Member
Border patrol boats have an the easy solution - a placard with purpose and contact information with an "if found, please contact...." notice. And, of course, advance publicity to the govt. of choice. Pretty easy to notify them if you have the GPS position from the spot device.

Cheers,

Wreno
 

Wrenow

Senior Member
That looks fantastic fun Wreno.
It is/was depending on whether you mean the RC Model Warship Combat battles we do monthly or the Maker Faire we attended.

The Maker Faire would be wonderful for any Picaxer, methinks. So many cool applications, so little time.

Wreno
 
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ljg

New Member
Dr. Acula,

Thanks for the link on the rubber duckies. I don't know how helpful the article will be towards building and sailing an autonimous vehicle, but the 69 comments afterwards was very instuctive of how a forum can go awry.

I laughed 'till my sides ached.
 

moxhamj

New Member
Yes, if all the rubber duckies fall off the boat because someone didn't tie the container down, then what is Ernie going to use for his song? http://www.youtube.com/watch?v=DiaKtHSAy7U

Seriously, I like the link to the submarine that moves up and down using oil filled bladders. No moving parts protruding through the hull. Thinking big picture, I am wondering if the original autonomous plane might be easier? Or an autonomous land based creature - maybe a robust sort of solar powered hexapod. Consider an ant which does a very good job of surviving in an unstructured random environment. I'd get into this sort of thing if I had lots of spare time and didn't have to work for a living and had my own university department with lots of undergraduates to help out...
 

Wrenow

Senior Member
Dagnabbit, DPG!

I mentioned your project to one of our members in the NTXBG, and now several of our members are thinking about how to do it. And considering challenging the AUSBG to a contest...... One even wants to set up a target and shoot at it when he gets there (he was voted down). They want to start with a lake vessel, move up to a trip across the Gulf of Mexico to Grand Cayman, then Galveston to South America. Ok, it is my fault for mentioning it.

Had a good battle today, complete with (very unusual) an accumulator rupture and a gas feed line rupture. Pics are at: http://picasaweb.google.com/wrenow/2007_10_28NTXBGBattle if you are interested.

You will note my son wearing an AUSBG World Championship 2005 shirt (the green shirt - though no, we did not make it). If you enlarge this one (http://picasaweb.google.com/wrenow/2007_10_28NTXBGBattle/photo#5126562552323324210)
you will see the AUSBG Logo.

Cheers,

Wreno
 
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