Long Range Wireless Buoy


#1

So I’ve been trying to figure out a good way to keep an ROV stationed around a given location without requiring active station keeping (such as with a boat controlled by an attentive captain or some sort of dynamic positioning system).

The general problem is that with any kind of wind or water current, a vessel on the surface (which presumably the ROV is attached to) will get pushed away from where the ROV was initially deployed, and even if the ROV itself has the ability to fight that current, the vessel it is attached to will eventually tug it away. Vehicles (manned or unmanned) that have to actively stay above a site are necessarily complex, so any way to keep an ROV on station passively is likely to be easier to implement, more robust and lower cost.

My thought has been that a simple way to keep station would be to employ a sort of clump weight that would sit on the bottom and would be heavy enough to stay put but light enough to be transported to a site easily. Presuming that the ROV would be examining things on the bottom, the tether would have to go this distance anyway, and the tether could be made thicker and stronger along this length since that portion would not need to be pulled by the ROV. This clump weight could be as simple as a hunk of metal that a tether goes through, or as advanced as a lander that houses multiple ROVs (similar to the one I drew in this post several years ago)

Of course, a drifting boat on the surface would still be likely to drag the weight, so instead, a cable running up from the weight could go to a floating radio buoy that is not big enough to drag the clump weight. If the buoy could be made to relay a wireless signal to a the shore or a nearby boat (which would no longer have to keep station precisely), I believe this system would allow ROV operations to happen with much less effort- especially in rough seas.

Some means for isolating the movement of the buoy from the clump weight would be needed to remove impulsive vertical loading from surge which could snap the tether and also to remove lateral loading which could cause the clump weight to drag). To address this, a float that is suspended from the tether several meters below the surface (which I call a “load stabilizer”) could be added to the system.

-----How it works----

As you can see from the photo at the top of this post, we’ve already built a prototype of this system which we tested briefly at Lake Tahoe a few weeks ago. Obviously a beautiful day on the lake is not exactly the rough conditions this system is designed to handle, but it’s a start. I thought I’d post a little bit more about how the system works…

Although the system could be made to work with simple WiFi, we chose to use a long range “Ethernet Bridge” system that is capable of communicating high bandwidth signals over several kilometers. We chose to use the RocketM5 system by Ubiquiti. For the buoy, we used an omni directional antenna, and on shore we used a 90 degree “sector” antenna. Here’s a list of our BOM for the radio system which ended up costing around $500 total.

1 RocketM5-USA 802.11N MIMO 5 GHz Rocket AP US
2 AMO-5G10 5GHz AirMax Dual Omni, 10dBi
3 RocketM5-USA 802.11N MIMO 5 GHz Rocket AP US
4 AM-5G20-90 90 Degree 5GHz MIMO 20dBi w/cables

This system works great (you can see us using an earlier non-buoy-based setup with these radios here). Effectively, using a set of these radios is like having a REALLY long Ethernet cable stretched between your two points of operation. The signal that goes in on one end comes out on the other. This is called a “bridge” mode, which worked great for us but there are many other configuration options to choose from if that’s your thing. The radios are powered with POE (Power Over Ethernet) and come with a wall-pluggable POE injector. On the boat (or buoy) side, where wall power is not available, we just got a 12v POE injector from Amazon and powered it using a USB/12v battery power supply.

I’ve attached a functional diagram below which I (of course) drew with MSPaint and am quite proud of.

One thing to note is that we chose to use hollow walled pipe instead of normal SCH-40 PVC because the weight of solid PVC was significantly greater. The pipe has a 4" outer diameter. Also, we ended up having the tether come out of the top of the buoy to make the electronics more reparable and reduce leaking risk.

Finally, not shown in this diagram is an additional 1" OD PVC pipe equal in length to the buoy that was made to dangle below the buoy an additional meter and a half or so with a few kg of weights on the end. This helped keep the buoy stable and guided the tether downward. The overall diagram shown as the second image of this posts depets this extension.

Here’s an image of the raw electronics used before they were mounted to the platform which would be slid inside the tube.

Here are those same electronics, ready to be placed in the buoy tube. A piece of hot water heater pipe insulation foam was placed in the bottom of the buoy to keep the electronics platform (containing the antenna) high above the waterline. An optimized design might utilize a longer electronics platform which would put everything other then the antenna as low as possible to help with stabilization.

During our Tahoe deployment we successfully operated ROVs attached to the buoy from our cabin on the shore several kilometers away. There is still a lot of work and testing to do. We must find ways to make the buoy sit more vertically, we want to try using a load stabilizer, and we want to test the system in rough seas. Once that’s done we may also want to add features such as a GPS module so the buoy can report where it is, a flashing beacon that makes the buoy easier to find, and perhaps optimize the buoy to be more easily deployed.

All of this is a work in progress, but I thought it would be good to post where we’re at and get some feedback.

Special shout out to Erika Bergman (shown below) who did most of the building for this prototype and was out with the buoy during our test deployments. You’re the best, Erika!


Wi-Fi Topside Adapter
GPS for ROV Surface Navigation
Remote control the rov
Underwater metal detector
#2

Hi Eric / Erika

First off really great concept, hope it gets some traction

A couple of things we drop a number of buoys over the side of vessels when looking for objects. No real science, but from a fair bit of trial and error, the units that have tended to float most up right and get the “most out of the water” are at about a 3 to 1 ratio (2 units out of the water 1 in the water). Additionally the heavier the weight at the bottom the better for standing the unit up (we normally core out a 250-300mm foam float to act as a sleeve to add buoyancy at the interface). Equally, just cut a hole in a bucket and fill it with space filling foam. Do not underestimate windage. Can most of the electronics be condensed down to the base (say 200m pipe) with then a 25mm linkage up to the antenna??. But, again more and then some more weight at the lowest base point.

I would also advise some form of anchor and some chain rather than just weight, it will hold better with less overall weight. We often use a 1.5kg folding anchor with less than 1m of lightweight chain and then some 3mm cord and it will hold fast a fairly decent buoyed system in some real current (but the narrow diameter of the cord makes it a little harder to pull up on the hands)

I wouldn’t go with a sub surface buoy to adsorb shock (I would on a moored boat) but we just use a reasonable large surface float. I would suggest that the equipment is just clipped to a tether (say 3-4m) back to that float (we again just use heavy duty game fishing trace and clips [say 400lb gear] but you will need a couple of swivels)

Scott


#3

Fantastic! Man do I wish I could have been there to see it work. Great progress towards opening up the use space. There are many people interested in stationary ROV research bases (especially when its cheaper than MBARIs MARS system LOL) Man, this would be a good platform even for limited range autonomy work. Scheduled expeditions, then when the researcher wants to look at the results/data, open a browser. Fantastic.


#4

@Eric_Stackpole Thanks for taking the time to do the write-up and equipment list for this project. You have a great working concept here and I was very impressed when I saw it working at Tahoe. I’ve already started ordering parts to start making up mine and I should have something mounted in the next month or so.

@Scott_W I think this was actually your idea when we were discussing the dynamic positioning problem months ago. In one of our brainstorming sessions, I brought it up with Walt and Eric as an alternate to having a support vessel maintain position. As you can see, they went with it! Now that the concept and equipment works, I’m going to try and mount a new communications mast to my boat and try this out in the ocean. I already have to deploy a buoy anyway to mark a shipwreck, this is just the next step.

Some other things I thought I would mention from my observations:

  1. I was very impressed with the speed and range. We were able to conduct full operations with the ROV from about 1-2km on shore, take that feed and upload it to the internet. We almost had someone remotely driving from the internet too! This is the only system I know of that is capable of such telepresence.

  2. Although the battery looks small, it was able to power the buoy for the entire day (6-8 hours) without having to swap out for a new one.

  3. In addition to the GPS module Eric wants to add, I made the recommendation to add in a way to remotely turn on/off the buoy/ROV combo. Anyone who has operated an OpenROV knows that reboots are sometimes necessary for whatever reason.

  4. We’re going to have to figure out what to do with the tether. Having a down-line to the anchor and a tether going down together is just inviting an entanglement situation. Eric’s “lander” approach solves a lot of the issues, but it will require a cage with a tether management system operating at depth. I don’t have a solution for that right now.


#5

You could use something like a Ethernet cable as the line. It is in no way ideal, but it is strong enough to start with and it will give you opportunity to see what you actually need from the cable/anchor line. Ethernet cable is cheap.

You could also thread a tether down a braided rope. I suspect braiding through a larger (than the 1/4 which i used) rope would be much much easier.

I am putting a buoy in Howe Sound tomorrow (no rov tether) so I have been considering this problem.


#6

Hi Eric & Brian,
I’m glad to watch a progress with the OpenROV idea. Fifteen years ago I’ve a small opportunity to spend a little bit of time & money for my home ROV hobby. My sample has been based on brushed DC motors, PIC-controllers and PAL-video camera. From first step I decided to use separate system with two motorized & battery occupied parts: a small boat carried coax cable reel , 900MHz video transmitter & RC receiver and underwater camera. There were an on shore TV monitor & 433MHz RC transmitter with own battery too. The surface on board controller duplicated the commands of camera’s thrusters for boat & reel motors. Of course my system was able be used on the calm surface. Maybe later I’ll be back in order to improve my experience for compensating a wave/wind moving by electromechanical features of cable reel controller on boat board. BTW could you tell some words re design your bottom tether store going to the ROV within yours wireless buoy realization ? How you won the tether twist & slack confusing ?
Hope to join to OpenROV community soon.
Best wishes
Vlad
vladarkhipov60@gmail.com


#7

Ok so I did a little research and took some ideas from Eric and the observations made and have come up with the Mark 2 design for the Wireless Buoy.

Additions:

  1. Float around main body
  2. Beaglebone Black for GPS and Tether Resets
  3. Lead dive weights mounted inside body

As for the float design, the half-cone/half-can design seems to come up most frequently and has my recommendation. Core out the center of it and it should provide the stability required. I’m not sure how wide to make it though.


#8

Hi

I think your project sounds amazing. I am currently working with similar project but I am using WiFi instead. There is a problem I am struggling. I don’t know how to p2p connect 2 device together. Do you know anything about it? That would help me a lot.

Many thanks,
Jackey


#9

Wow!
Ideas come in quick. My 1st thought looking at V1 design is that it would be great on a flat bottom but if you had reef? you would have a nightmare of tangled tether line. Having the tether from the surface down to the bottom leaves the majority of the tether mid water & free from entanglement. Also with the surface Buoy would it be possible to weight it with replaceable batteries that could feed the trident if desired or if batteries in Trident were flat? As we cant replace the batteries in the Trident this would expand it operational time & also allow to put a much bigger capacity power supply to feed Trident & also manouver or stabilize the Buoy.

If I was using my boat out on the water I wouldnt need a surface buoy because I would use my autopilot anchor lock feature on my MotorGuide Xi5 Electric motor to keep me still in current. One vertical shaft that rotates with a single propeller & stays in position with GPS. With the remote control I can one click to move it 5Ft at a time in any direction. https://www.youtube.com/watch?v=85LpqahGXvw&feature=youtu.be
Now this is a overkill obviously for a surface drone but it has simplistic concepts that is already working in the real world & it is use to keep my 18Ft boat stable in high currents not a small buoy lol

It seems to me that locking it to the bottom means you are already in a boat to move its location, but I thought if you are remote to the surface buoy then you would need to be able to control it & move it. Using GPS to keep something in position is also done on tiny quadcopters and are cheap as chips. Using already designed technology means youre not reinventing the wheel & its the size of you thumb.

Just thought I would share my thoughts to try help in the brain storming

Cheers
Mark


#10

@Eric_Stackpole,
All of the M5 datasheets indicate that the M5 runs on 24 vdc @ 1 amp yet you are running the M5 on 12 vdc.
Please explain.
Regards,
TCIII AVD


#11

We run through an inverter and plug the M5 power over ethernet adapter in to the inverter.


#12

@Brian,

Thanks for the clarification, much appreciated.

Regards,
TCIII AVD


#13

I am a student researcher; I am working on my Ph.D., which is about sea cages for aquaculture. I want to extend the wifi from an office in the land to sea cages 2km far away, in the sea. My goal is to use the wifi for sensors data collection and video surveillance.

I will setup one as AP and the other in the cages as a client

So now I am stuck I can’t setup the Wireless link between the land and a sea spot (where the sea cages are placed)
so my question is how to setup a connection between the office and the sea cages which are 2km away from the office), so I can do video surveillance and sensor data collection?
is this material you did use in this buoy wifi can be used in this situation and works?
thanks for helping me :slight_smile:


#14

So the setup we used can easily go 2km. Assuming you have a solution for providing continual power at the “sea spot”, I don’t know why it would not work. What was the issue you ran in to when trying straight wifi?


#15

the problem is that i can’t use 5ghz only 2.4ghz is this will work?

also can you provide me with the detailled list of the solution you used?
thank you


#16

Hello,

i am building a buoy for video surveillance 2km from offshore.

i have some license limitation on using the Ubiquiti antennas here in my country.

i did check some other networks very low power technologies like loraWan, LTE-m etc… but they still have low bandwidth <1mb which is not enough for video streaming.

do you know about some technologies that can help me build this buoy 2km from offshore for video surveillance like 24h/24h and low power consumption minimum 1 week?


#17

Here is a link to a data buoy that I reference nearly every day when it is in the water. Due to the ice conditions here in Lake Michigan, the buoy is pulled every fall and is currently out of the water. You may want to contact the people involved in this project for the technical assistance you are looking for.

http://uglos.mtu.edu/station_page.php?station=45026


#18

thank you for helping me i will contact them asap


#19

can you give me an email of a member of this team?

i did conact them in this email cookinfo@aep.com and i am not getting any response.


#20

Try this contact rwsawtel@mtu.edu