IMU problems


#1

Hi everyone. I'm new to ROV. Just finishing my build. I have an expensive aircraft part to recover from a high mountain lake i need to get done before freeze up so I am time limited. It fell off the aircraft on take off on floats. Value $40,000. Its too deep and too high for a diver. ROV is my only real viable option.

Most recently I installed the IMU and when we modified the code it basically killed the ROV. Battery indicator showed almost dead batteries even though they were fully charged, and nothing would work.

My buddy who helped with the code came by this past weekend and we backed the changes out of it and all is well. I still have a few minor bugs to work out, one thruster runs one direction only, and the camera freezes often, but at least its alive again with the IMU turned off.

I'm going to verify my connections to the IMU but I was careful to get them right when I installed them.

Since the IMU is potted I cant do anything with it. If its defective I may have to order a replacement.

Anybody have this problem before?


#2

Hey Rick,

Would love to follow the play by play on the recovery operation!

As far that the IMU goes, what version of the software are you using. The default that is installed on the beaglebone, or have you burned a version on a SD card?

Assuming you are using the 2.5 stable build that was shipped on the beaglebone, can you elaborate on the symptoms a little more when the IMU is enabled:

1) Did the cockpit software load in the browser?

2) If it did load, did you see telemetry on the right hand side?

3) On the lower right hand side, we have system time and run time. Is run time progressing continually or constantly reseting?

-Brian


#3

It’s the latest version Brian, 2.6. The instructions say to download Putty and modify the code in two places. I had a buddy do that for me since I’m more of a nuts and bolts kind of guy.
The cockpit loads in the browser but battery indicator showed dead or near dead batteries, even though they were fully charged, and the rov was dead. Lights lit up on the board but nothing worked. We backed out the code changes and it came alive. I still have one thruster that runs one direction only, and I can’t get the lasers to come on, although I’m not overt concerned with the lasers for now. The thrusters obviously I need to be able to control. I can’t remember if I get telemetry if it dead or not, but with code restored to original I do. I’m just learning the cockpit so may have missed a thing or two. Last issue now is the camera takes a single frame when the software starts and displays that still forever. Not much good like that. CPU usage varies quite a bit and seems high to me. Without any commands input CPU runs 50-70% and occasionally up to 100%. Probably why the camera freezes.
Thanks for the interest and any suggestions you may have. Hope to get some more troubleshooting in the next day or so.


#4

This is an interesting scenario, how do you plan on recovering said item?

Have you tried a manual upload of the image via SD card? I had to do this on my ROV. I had to get a microsd card, format it, download the full emmc image from git hub then burn the image to the sd card, remove the beaglebone from the main assemby, plug it in via usb to my computer for power, and hold down the "boot from sd" button (http://beagleboard.org/getting-started) then wait for the lights to go solid after 15 minutes. This solved my issues, and now I login to the dashboard (192.168.2.1 without the port number) and use cloud 9 to change files, lots easier.


#5

I’ll try that if the new IMU the folks at Open ROV sent me doesn’t do the trick.
My recovery plan is fairly simple, and of course a theory only at this point. I intend to have a hook of some sort dangling from a bar attached to the rov, in view of the camera, with a separate cord to the surface. If I can position the hook under a lip of the part I’m hoping to pull it up with the cord. Attachment to rov would be a break away type, possibly Velcro.
Time will tell. Thanks for the input.
Rick.


#6

Hi everyone. Ran my ROV in the water this past weekend and the new IMU fixed the issues with the last one. One bag egg I guess.

Anyway, mostly successful dive, although running in a straight line seems overly difficult. I need to try a lower thrust factor next time. Also need to work a bit with ballast and balance. Biggest issue was orientation. I see other discussions re compass calibration and I don't really see any definitive answers. The calibration button doesn't seem to do anything, and the display is erratic and unreliable. I think if I could get it calibrated and displaying all IMU data properly it will be a treat to fly.

My earlier issue with motors not running in both directions turned out to be a calibration of the ESC issue. I had done the programming and calibration earlier with success, but for some reason the port motor went out of calibration and zero thrust was at about +1.5 on the scale. It took tries to bring it to zero, first calibration halved the error, second one did it.

When I had the bell off I noticed one of the wires in the bundle had been rubbing on the bell and the insulation was worn through. It was one of the wires from the battery tube, so power may have found its way to the bell causing the calibration to go off. That's my own theory. Its rather tight around that bell so I re-routed the 4 wires to the IMU and the 2 spares above the motor and along side the vertical thruster to provide more room. All is well now.

Thanks to all for your help. Looking forward to tips on calibrating the compass properly.

Rick


#7

Hey Rick,

If you update to the latest RC3, I've disabled the mag again in prep for the release. The gyro is supper stable. The current workaround it to point the ROV North when starting it up to have the compass point north.

The larger Mag updates are a bigger affair.

-Brian