Alternative to Optical fiber slip ring approach


#1

My name is David I am in my final year of robotic engineering in college. For my final year i have been given a project to complete in terms of robotics. My problem is the control of the length of fiber optic cable for a fiber opticaly controlled rov. The robot will be powered by an on board battery later so power is not a problem. The Optical fiber will more then likely be a single strand of single mode fiber as that is the most available in my college.

The project is to design and make a means of controling the length without the use of a fiber optic slip ring by implemeting some sort of a reel like aproach. It can be hand wound as automation can be dealt with at a later stage.

Though i have found small bits of information talking about these slip ring alternatives i have been unable to find any examples of them being used or any designs or detailed explinations about how they work so it is very hard to understand what is being said and hence begin designing my own solution. I have recently been looking at David Camerons set up with their ROVs Jake and Elwood but again i cant find designs or detailed explinations of how it works.

As i have to actuallly create this reel and test it in a lab I am very worried that I will not be able to complete this task. I realise this is a bit of a stab in the dark but if you could offer any information to help me it would be greatly appreciated!

1938-ghostsoftheabyssarticlejakeelwood.jpg (33.1 KB)

#2

I have a suggestion that popped into my head: fishing reel principle. http://en.wikipedia.org/wiki/File:Fishing_reel.svg

Just at a larger scale, and instead of the reel itself going up and down, you can drive a level wind screw to put the layers.

a basic setup could consist of two servo/stepper motors so you can make the proper curve to put the layers correct in relation to the drum width. this is common on larger winches. just that async motors + encoders are used with VFD controllers.


#3

SAAB in Sweden have made a TMS without slipring on their Seaye Tiger system.

http://www.seaeye.com/type2tms.html


#4

I have pictures and close ups of this kind of systems. I can mail them to you if you like.


#5

Please post them on the site! I'd love to see them, too.


#6

Hey ya that would be a great help if you could mail or post the close ups!

Thanks thomas S i was thinking of the posibility alright of a fixed reel with some sort of rotary arm kind of modification for guiding the fiber.

Thanks also Sven H I couldnt find anything like that!


#7

My first idea was that i would take the spool of a garden hose reeling system from any home depo store and use that as the starting point because it is the only spool i can find bigger then that of a very very expensive deep see fishing reel which is in no way in my budget. i was then thinking or attaching some sort of an arm onto the side where the fiber would come in that would slide left and right on the arm so as to spread out the fiber minimizing overlap. but i dont know wether or not this would work due to the twisting of the fiber if it is a single strain of single mode fiber. Or even if this would matter as long as the reel is big enough not to cause the fiber pass its bend radius. I have all the necessary machines to create metal pieces but unfortunately i have not done any metal work experience so i see this arm if it even works as something that will take me a long time to figure out.


#8

David,

Have you considered a wireless router inside the spool connected to a fiber media converter?

either can be had on EBAY at a reasonable price.

You might go with large diameter PVC pipe to fit the electronics in and disks fabbed out of PVC sheet on the ends to make a reel...

r/

Mike


#9

You’d still need to power the router inside the tether drum so power slip rings would be needed anyway. the issue with the bail arm type TMS systems is that the tether has to be " pushed " out of the TMS itself. The Sea Eye tether is about 18 mm and is pretty rigid. using a thin wire will probably result in serious bird caging. these TMS’s have several tensioning mechanisms fitted.


#10

Mike, that is great idea for a surface supply reel. The fiber optic rotary joints I have seen cost around $1500 - $4000. So a $50 Ethernet to WDM Fiber converter, a $20 wireless bridge/AP/Router like the TP-Link WR-702, and a battery would do the job and let you keep the computer out of harms way on the boat. Stick it all inside the reel or on the outside with a long axel and you could always swap batteries if needed. Bob