Underwater ROV - Questions about building an ROV

[gascan]

[color=#000000]Hey, folks! I recently joined the UC Davis Underwater ROV team, to build and compete an ROV at an annual competition in NASA Johnson Space Center's Neutral Buoyancy Laboratory in Houston, Texas. Since last year was (apparently) a total disaster, we are starting from scratch this year. I am doing research on various design change possibilities, so I will be asking a whole bunch of questions on here until the competition is over.

Right now, I am investigating the possibility of going wireless. Since last year the power/control cable leaked and short-circuited, we would like to run wireless if at all possible.

Question]

[jsl]

How about ultrasound?

It'll be enough

How about ultrasound?

It'll be enough for controls and telemetry, but you'll have a serious problem with the huge amounts of data from the cameras.

Besides, the only radio signals that will penetrate salty water in an orderly fashion is ULF signals. But their wavelength is in the kilometer-area, resulting in an extremely low bandwith.

That's why they all use cables...

[scott t]

If your budget permits what

If your budget permits what about using fibre optics as your control cable?

I know somebody out there has figured this one out, but here is the question. If you used a hose that is air filled would a radio signal be able to travel through it even if it is curving? Or do radio waves only travel in straight lines?

Scott T

[gascan]

all very interesting ideas. Ultrasound

all very interesting ideas. Ultrasound for control and fiberoptic cables are both excellent solutions. The competition is in a gigantic neutral buoyancy lab, and I do not know what type of water it uses, so I will still pursue wireless of some form. is it possible to use multiple sonic frequencies to transmit multiple streams of data? Also, what equipment would be used for transmitting and (more importantly) receiving this type of transmissions?
Gascan

[tmsmalley]

If you are going to

If you are going to try to go wireless, better test the specific water body you plan to operate in. Heavily chlorinated and "salty" water blocks radio signals. That's one of the reasons why ROVs tend to be tethered.

Try a Google search on "ROV". There are several ROV websites that may be of help to you more than our group. We tend to stay shallow since we like to see our boats.

[jsl]

Also, what equipment would be

Also, what equipment would be used for transmitting and (more importantly) receiving this type of transmissions?

Yours, of course!

You would have to custom build everything yourself to suit your specific application, all of the hardware, and you would have to develop the rather sofisticated data transfer protocols and modulations yourself to get any datarate out of an ultrasonic link.

But regardig hardware, a pair of simple ultrasonic transducers would do the trick. The challange is all of the hardware and software behind them.

But I have changed my pick. Double secureity. The fibre optic link is more than sufficiently fast to carry the camera data as well as controls, but som pretty descent processing power would be needed to hack up the live camera feed and relay them back up realtime without noticable delay. And then the ultrasonic link as a backup for telemetry and control.

[gascan]

Its been a while, and

Its been a while, and we are well under way for developing the ROV's. However, we have focused on the mechanical aspects of the design so far (all but one of us are mechanical engineers...) and have held off on the control and communications aspect. Preliminary tests suggest that wireless control should work on the short range we will be dealing with, using standard hobby radio equipment. We have not gotten any wireless video cameras yet, and have not been able to perform any tests of our own.

I saw an article by Dave M. about his experiment with wireless cameras on his sub.

http://www.rcgroups.com/forums/showthread.php?t=339195

Does anyone know what what range he (or others) was able to get with his system?

Gascan

[Guest]

My antenna has to be

My antenna has to be just out of the water for my wireless color CCTV picture to be transmitted to my receiver/monitor on shore, at 1.2 Gh. This $50 unit has been working in the waterproofed sail of my L.A. for several years. I can read an underwater sign 40 ft. away, with the camera lens just under the pool water, and the antenna just out of the water. Standard wireless won't work for your application, unless you can float an antenna up to the surface, while your camera is 50 ft. down.

[carcharadon]

I've had my subs down

I've had my subs down at least 30 ft and possibly more. I've used frequencies of 27 mH and 74mH and it doesn’t seem to make a difference. The subs do not have a wtc with control rods or shafts to seal so there is no concern for leaks. I’ve noticed however that in a pool responsiveness is severely limited compared to operating in fresh water.

http://www.rcgroups.com/forums/member.php?u=40728

Gascan, if you look at the 4ft pool video, especially where the sub is coming up, and imagine that there is another bilge pump directed straight up located where the hatch is just behind the dorsal fin, this could be used to create a hover or to send the sub directly down with out the need for forward motion. Also once hovering under water it can turn on a dime. This in effect would be an ROV and I plan to make these modifications to the next 4ft model I make.



Edited By Carcharadon on 1142341127

[himszy]

Erm http://www.subcommittee.com/forum/icon_question.gif , not sure

Erm , not sure if you've covered this or thought about it, but you can't have a wireless ROV, as the R stands for remote (ie some form of physical connection)...

Michael

[Guest]

I disagree.

ROV simply means that

I disagree.

ROV simply means that the operator is situated a way from the vessel, as opposed to a manned submersible etc.

Strictly speaking, just about all model subs are ROV's.

Andy

[aeroengineer1]

Hey, I am interested in

Hey, I am interested in finding out more about this competition. Maybe I can use some of my hobby skills and get some credit for it. Who sponsors it and it there a website that would give more information.

As far as the "R" standing for remote, there are many definitions for that Michael, but the most basic refers to operating something from a removed location, there is no inference as to the method. In fact what is that little box called that is used to control the TV, that is right a remote control. An infrared device.

Adam
Aerospace engineering major at ASU



Edited By aeroengineer1 on 1142371848

[himszy]

Well then you learn something

Well then you learn something new everyday.....

Adam,

http://www.google.co.uk/search?....s&meta=

Michael

[gascan]

The first link on the

The first link on the google search is for the Texas regional competition. My team and I will be participating in the national competition. MATE (Marine Advanced Technology Education center) cooperates with NASA to put on a series of ROV competitions for highschools, colleges, and universities. Heres a link for this year's competition, though I think its too late to enter.

http://www.marinetech.org/rov_competition/2006/index.php

It doesn't sound good for wireless, but I need to find out more before I can give a final yes or no. What info, other than the frequency, can you tell me on the camera, transmitter, and reciever used (power, range, etc.)?

thanks!
Gascan

[Guest]

Gascan,
My cheepo small camera and

Gascan,
My cheepo small camera and transmitter/antenna come as one unit, powered by a single 9V battery and the whole assembly fits into the sail of my L.A. The range is stated as about 300 ft. The receiver is also powered by a 9V source. An A/C adapter gave some interference, so I use a 9.6V AA battery pack to power the receiver. That connects to a VCR and T.V. monitor on shore, and with some delicate tuning, I get a pretty good picture. This is with the antenna just above the water surface.
The videographer from the Outdoor Channel took some footage from my receiver to lead in to the "Inside R/C" TV show about SubRegatta '04.
See photos of the sail with the camera on the L.A. folder on my web site, Art Broder's Models, or click on the green globe below.



Edited By Art Broder on 1142406672