My ROV

[kenl]

Hi rovdude, two of the O rings fit between the outer hull and the back door, the third gets clamped between the door and the rear flange, much the same as a gasket would. In the picture the third O ring should have been a bit larger than it was so it's not obvious where it fits.

I have since hollowed out the door so as to reduce weight as I was having difficulty balancing the rov and keeping a low center of gravity. Next time I open her up I'll take some pictures.

[rovdude]

I've been doing some research on IMU's and (now all in theory ) :

The accelerometer should work in any water conditions. Have it start running on the dock (not a floating one) so we have an initial velocity of 0. Integrate once to find velocity, twice for the distance traveled. If the acceleration = 0 at any point, we can assume velocity is the same as the previous reading.

Coupled with the gyro (integrate once to get degrees), and a GPS to get a starting position, we should be able to use vectors to keep track of where it is going.

Now this is all in theory... IMU's have a lot of noise, but there are also filters that can be applied to keep relatively clean data, which I think will be good enough for our purpose.

I would think an accelerometer would only work in relatively still water with no current though, right?

Wouldn't the accelerometer notice the change in velocity when it gets in the current? And then once it's in the current, wouldn't it read a zero acceleration, meaning it is moving at the same velocity? I'm probably missing something

[kenl]

Hi Rovdude,

I'm not really sure on the maths side it to be honest, I haven't even given it any thought yet. What I can say is look at some of the rc helicopter and airplane flight controllers, things like multiwii and the Ardupilot use both the gyro and accel to hold the position and attitude of the craft. The code is open sourced and is Arduino based though most of it now is leaning towards needing a mega board to run it, it is also very complex code by my standards. What I do know from playing with quadcopters is that the whole setup is VERY sensitive to vibrations, and will wander if not aided by GPS, Optical flow sensors and sonar devices in the case of altitude.

Ken

[kenl]

Continuing on with the topic of navigation..........

At this stage I'm still trying to get my OSD sorted out so that it displays a more intuitive method of navigation. I had the ROVs' bearing displayed on screen, I have since changed that to have the OSD show cardinal points, this is the lcd version

        lcd.print(heading);
        {
          if(bearing>337.5){
            heading = "N ";
          }
          else if(bearing >292.5){
            heading = "NW";
          }
          else if(bearing >247.5)
            heading = "W ";
          else if(bearing >202.5)
            heading = "SW";
          else if(bearing >157.5)
            heading = "S ";
          else if(bearing >112.5)
            heading = "SE";
          else if(bearing >67.5)
            heading = "E ";
          else if(bearing >22.5)
            heading = "NE";
          else
            heading = "N ";

which requires less mental arithmetic when out on the boat but I will soon write some code to show the ROVs' orientation in relation to the boats.

I don't know if it's just me but once you launch the rov and it well out of sight it becomes quite a chore to know which way it's going in relation to your self. For example it may be out off the starboard side, you know that because that is the way the tether is going, and you know that the ROV is heading SW and that the the boat is facing NE, but to know what the ROV is doing in relation to the boat requires a mind quicker than mine.

My plan is to align the ROV with the boats keel when at anchor and zero the compass heading by subtracting the current heading from itself, then when the variable is between 337 and 22 degrees I will have the OSD and LCD display an arrow facing up etc.

It's all just theory at the moment but I hope it will help me with navigation, because I really struggle with it.

[Erik102696]

what are you doing for your thruster housing? im working on making some brushless thrusters but the housing has stumped me.

[kenl]

The basic design of the thrusters is in the Thruster section of the site

viewtopic.php?f=3&t=1276

[rovdude]

I honestly haven't tried it yet because I haven't bought the board, but check out my ramblings on how to figure out navigation for an IMU viewtopic.php?f=16&t=1374. There is more than one way to do the math for navigation, but I think I'm going to go with the calculus route because it is easiest for me. If you have any questions on it you can message me. There is also a method using matrices, which to me is very complicated (I haven't learned that yet) which can at least find Euler angles, not sure of anything else. Hope this was helpful

[kenl]

Well after a long absence I decided to get the ROV out and do some work on it, last night I ordered some new parts for PPM control using a standard RC radio. I also dug out a Video Tx and Rx to hopefully solve my video problems I was having.

This will also allow me to have a wireless tether reel in that there will be a Rx for the radio and Tx for the video inside the hub spinning at will.

So I put my ROV on charge and after about an hour BOOM!!!

Boom1.jpg (599.54 KiB) Viewed 4623 times

I think I may also review my battery charging method, I knew it wasn't the best to charge the packs in the ROV.

Anyways I was very lucky not to have gotten hurt, at the time it exploded I had just placed my hand on the side of the case to see if it was warm, not much hair left on that arm but my eyebrows are still intact.

[scubersteve]

Wow

[sthone]

WOW is right, glad you didn't get hurt.

Thanks for posting though this points out some of the dangers that can occur with any hobby.

-Steve