I was wondering if you’ve given any thought to some type of positioning system for BlueROV2.
Right now the only method I have for diving my current ROV(OpenROV) is to drop a weight, line, and buoy as a marker and follow it down. It would be really cool if you were able to eventually build some accessories for the BlueROV2 (as I plan to purchase one very soon :-)) Things such as positioning system(some type of sonar), gripper, magnetometer, etc… that we can optionally purchase and add on would be a big win!
Thanks for the post! We currently do the same thing with a drop weight and a marker buoy. It works pretty well and it’s relatively easy to hit your target. We would love to add a real positioning system in the future. The typical way to do this right now is with a USBL positioning system but those are very expensive.
We’re working on a bunch of accessories for the BlueROV2. We plan to spend most of our time for the next year making the BlueROV2 as useful as possible. That includes things like a gripper, sonar, sensors, etc.
I would love to hear other people’s suggestions for accessories that they’d like to have as well.
Don’t be ashamed of the marker buoy system, I still use it until there is an affordable positioning system out there The pros who lack a positioning system still use this method. I know it’s clumsy and a bit difficult to follow down in high current, but it still works. It also gives me a surface reference when I am trying to anchor the boat close to the target site.
In the intermediate until there is a NAV/positioning system, the GPS function of ArduSub works great for surface navigation. It has application if you are making a lot of dives in fairly shallow, calm water so you don’t need to throw out a bunch of buoys. For deep water though…we’re still using the buoy and we’ve landed within 8 feet of a target in 80 feet of water.
I took a stock 3DR GPS module and mounted it on the port side on top of the Fathom X board. I also attached and connected the I2C splitter that came with the Pixhawk to the starboard side so I could have GPS and the depth sensor. When you calibrate your ROV, you will need to disable “Compass 2” (the one on the GPS module) or else you will get a mismatch error.
We’ll be testing this in shallow water this weekend, but the concept of operations will be to launch the vehicle, drive to a point of interest with GPS aiding, commence the dive, and then switch to the video window in QGC for the dive. We’ll see how it works.
I’ll be interested to learn how your testing goes. My BROV2 floats fairly high on the surface so I wonder if that will be high enough for the GPS antenna to see satellites?
On work class ROVs we use USBL or LBL depending on the accuracy requirements for the positioning of items on the sea bed. However if we use equipment mounted on the ROV like a multibeam echo sounder which has a high ping rate and covers a wide swathe of sea bed. We have to use an inertial navigation system.
The INS basically is a dead reckoning system that is very accurate but tends to drift over time thus it is updated with a USBL position. I have used in the past smaller commercial AUVs that require a GPS position prior to diving then once dived use dead reckoning to position themselves subsea, with commercially available INS. As I mentioned it does drift, but is good enough for recce surveys.
To build an INS you need accelerometers in three axis and gyro compasses in three axis. Doesn’t a modern smart phone have these items installed in the first place?
I was wondering if you were able to do any testing on your setup this weekend?
Also wondering if since you had to disable Compass2, does that mean that when you submerge and lose GPS, do you also lose the onboard compass? (this may be an ignorant/silly question on my part, though I’m not yet familiar with the inner workings of the BlueROV2).
We didn’t get a chance to test my set-up this weekend, I still have some video issues to work out. When I get a chance to button everything up, I’ll toss it in the pool or out on the boat again and see how it does.
You don’t lose the onboard compass because there is also a compass on the Pixhawk (Compass 1), which is the standard for BlueROV2. And you have good questions, I’m still trying to figure out all this stuff as well.
Surface-based GPS units don’t (currently) tend to work well with ArduSub, because the GPS signal is lost while underwater, and gets distorted when just below the water surface (causing very large position offsets that make the ROV jump around on the map). There’s some more discussion in this thread.
The pros who lack a positioning system still use this method. I know it’s clumsy and a bit difficult to follow down in high current, but it still works. It also gives me a surface reference when I am trying to anchor the boat close to the target site.
