Navigation & Tracking

[seawolfdiving]

I am currently involved in the design & build of an Observation Class ROV for an upcoming scientific exxpedition in the shallow (60ft or less) near shore waters off the coast of Florida. The expedition will begin in July of 2012.

The purpose of the ROV segment of the expedition is primarily educational outreach.

The ROV project is self-funded and budget is very limited. The individuals involved have very little previous experience at ROV design/operation. The goal is to use off-the-shelf technology but in perhaps novel ways in order to build and operate an observation class ROV. The system is to have certain restrictions & limitations. It must be 12 to 18 VDC power. Must be entirely digital with exception of power supply. Must include navigation instrumentation (compass, depth, speed). Must be able to make water quality observations (pH, temp, salinity/conductivity, DO). Must be able to take water/sediment samples. Simple enough, right....

The idea is to design an unit that would operate at something above the level of the typical camera & analog ROV units currently offered as school projects. The unit should be affordable to the average highschool/ junior college science budget, within the technical abilities of this age group and education level, challenging but not impossible.

The design and build team was selected intentionally with limited experience in order to evaluate the provess as to age/experience appropriateness and feasibility.

We have been fortunate in that we have gathered almost all the necessary components and found reliable sources for everything that we need with few exceptions.

What we are looking for now is a means to track the unit while it is in the water. This is usually done via an Acoustic Tracking System such as a SBL or USBL system and possibally coupled with a surface GPS system.. The current market price for such a unit is way out of our target budget.

I am soliciting ideas for alternative (and affordable) tracking systems.

Any Ideas?

Thanks

Ron sends

[SoakedinVancouver]

"...The unit should be affordable to the average highschool/ junior college science budget..."

And that would be between what and what in your area ?...

[thegadgetguy]

Yea, this sounds a little expsensive for anyone I know...

[SoakedinVancouver]

3 buoys, with underwater "antennas", and underwater sound pulses from the ROV. Time of travel of pulse triangulation...?

[seawolfdiving]

Considered using a fish finder... The problem is that the unit will be operated from inside an underwater research habitat at 60ft depth. Fish finders work great if on the surface looking downward, and over a narrow field of ops, but I don't know how we'd use one at 60ft... :

[SoakedinVancouver]

Release of flashing (miniature strobe light, ultrabright LEDs, 3 per egg) "eggs", popping at the surface, at regular intervals? Have the flash(es) in group, indicating which egg it is (the first egg flash once /5 seconds, the second twice/5 sec., etc...) in case you don't pick 'em up in the right order... Or bright AND biodegradable devices, numbered?

Release of an oil slick would be a no-no (I am assuming you are not backed by BP...) but appropriate dye might be useable and cheap? (Now, a release of floating french fries is a no-no because of the oil slick, but following the flock of seagulls going nuts would be fairly efficient, me thinks...)

Have a slave boat on the surface, with an umbilical to the ROV, and tracking said ROV manoeuvers. It would require an umbilical drum with appropriate controls, but that's more engineering for the kids to get acquainted with! Use a thin fiber optic as the umbilical, to keep the ROV somewhat nimble at maximum depth... It would also let you use RF to control the ROV, by using the surface unit as an RF-to-Fiber interface...

How clear are the target waters? If clear enough to see the ROV from the surface, have a hobby R/C aircraft rigged with a camera and a GPS unit, transmitting back the aircraft coordinates to the mother ship. Want precision? Rig a green laser on the back of the ROV and a green light trigger on the belly of the aircraft, sending the GPS data only when flying over the ROV position...

I am getting more and more expensive here, let me get more coffee in my system...

[SoakedinVancouver]

"...the unit will be operated from inside an underwater research habitat at 60ft depth..."

Talk about an innocuous detail!

Triangulation with 3 "antennas", (use the habitat as one of the three?) and hydrophonic (?) pulses. Triangulate based on signal time-of-travel. I would not be surprised if such system has been used by previous users of the research habitat, talk to the people running said research habitat.

Serious stuff, sorry about my somewhat lighthearted (but all feasible!) suggestions, ; )

[SoakedinVancouver]

Me again. The only part of the fish finder that would be exposed to the 60 foot depth pressure is the "coil" head, which, as far as I know, is potted, therefore impervious to the pressure. It is coupled to a digital device, sending out the pulses and interpreting the data. So the main challenge would be to intercept the interpreted (ideally) or raw (more challenging) data and transmit it back to the operator console.

By the way, the cable between the head and the ROV has to be pressure/water penetration proof (junction box with the cable opened up, down to the copper, and then filled with epoxy). This stops water from reaching the ROV's unpressurized innards.

I just noticed that I am assuming we are talking about an ROV controlled via an umbilical, not an AUV (autonomous underw...), please confirm that?

[SoakedinVancouver]

Im baaaack!

Could you use the fish finder from inside the habitat, to "spotlight" the ROV? Why is it only now dawning on me that this was your intent in the first place, as opposed to run it from the ROV and "recognizing" the immediate environment and therefore knowing where the ROV was...?

Either way, ask the manufacturers about the depth rating of their heads, I would not be surprised if it is in excess of 100 feet. These things do fall off the boats sometimes (no, I never lost one personnally...), since a lots of them are of the temporary mount style.

They are power hungry though. A thin pulse of 100s of watts. It adds up.