Pixhawk Rover/Boat Possible Interference In Water

I apologize in advance as this will be somewhat long winded, but I want to try to provide as much information as possible to hopefully find an answer...

We have a Pixhawk with 3DR uBlox setup as a rover. Initially we tested the system on an RC truck, just to make sure we could get everything working the way we wanted, before we moved to our long term goal, which was setting it up in a boat. The truck worked near flawlessly, so we moved everything to our boat, and now we're starting to see major issues.

Our first trip to the lake was last Thursday, and pretty much nothing working properly. We couldn't even get simple functions such as reverse to work properly. So, instead of wasting time, we decided to come back to the shop and just redo the whole setup with everything in the boat as it's intended to be. After that, everything seemed to work properly. Switches, control surfaces, GPS, arming, etc. There didn't seem to be any issues. While that information may not be important, I figured I'd add it just in case doing a re-setup would be a suggestion.

Fast forward to our second day out at the lake. On our first attempt at putting the boat in the water, it seemed like the boat had almost no idea where it was at, although MP showed everything as correct (location, heading, etc). When switched into Auto for it's mission, it would go completely in the wrong direction. So, while on site, we decided to redo calibration, compass, etc just in case it was something going haywire from being so far away from our shop. After that, we put the boat back in the water, restarted the system, and things seemed to get even worse. And really, this is where it gets tricky/confusing to me...

If we pull the boat out of the water and start the system up, everything seems to work perfectly. The system initializes, we get GPS lock, arm, etc...all within maybe 15-20 seconds. Everything looks good in mission planner as far as direction, heading and all that. 

If we put the boat IN the water and start the system up, everything acts funky. The Pixhawk boots into the "police lights" and takes nearly a minute just to start seeing satellites. And once it actually gets GPS lock, it doesn't take but a few minutes for it to seemingly lose GPS. It's strange though, because the green light on the Pixhawk stays lit, yet mission planner says it has no GPS signal.

Regardless of which steps we take, the boat will only do 1 of 2 things. It will either head the complete opposite direction of the waypoint, or it will simply go in circles and nothing else. Even if we go through the entire setup on land and make sure it's GPS locked, then set the boat in water, we get the same scenario. It's like something is interfering once it gets set in the water, but I can't imagine what it would be.

We're doing all the testing at a private lake community in town, and the height difference from land to water isn't more than maybe 6" so I can't see that being a factor. These lakes are also extremely open in just about every direction, and we even took it to another lake just to be safe, but had the same results.

What makes it even more strange is that if we try to do a "Learned" mission manually via the transmitter, it still doesn't respond correctly. I can input the waypoints via the transmitter, they show properly in MP and everything, but once you set the boat in Auto, it acts like it's lost again. It does the same thing of either circling or heading in the wrong direction.

My only other thought is to get the system outside of the boat on a raised platform or something similar. However, I'm not confident that will do much because we get solid lock on land almost instantaneously, and we've even ran the boat with the top cover/lid open, so the whole thing was completely open to the elements with no change. Not to mention, I've watched videos of boats working without a hitch.

 

At this point, I'm kind of lost on where to go. We spent a total of about 4 hours at the lake, rebooting, redoing missions, etc...and everything led to the same results. I'm positive that there can't be anything wrong with our Pixhawk system as it worked beautifully on a truck. I also know that the boat itself works, as we can manually move it around the lake perfectly. 

So, now kind of I'm grasping at straws and open to any suggestions anyone might have. Even if that means trying out a completely different controller. A huge thanks in advance to anyone who might be able to help!

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  • Hey guys, thanks for all the input! I think there's definitely something to the rudder mentioned here....

    When I took the boat out and drove it in manual mode, the rudder was in fact reversed. I didn't think much of it, and just simply switched it on the DX9 radio itself. Off the top of my head, I can't recall if it was set correctly via the Pixhawk, but I did redo virtually the whole setup, and could have overlooked it. If I did, that certainly makes sense why it can't head in the right direction.

    I will get the boat hooked back up today and see what's going on, then hopefully get some testing done at the lake Monday. If I still run into issues, I'll load up the logs and photos as requested.

    Thank you all again for the help!

    • You can easily bench test this at home.  Put the boat in steering mode.  Next pivot the bow to the left about 30 or 40 degrees.  The rudder, or rudders, should turn in a direction that would steer the boat to the right.  If it, or they, move in a direction that would turn the boat to the left then you would reverse the "roll" direction in mission planner.  You would probably also un reverse your transmitter .  Any further problems really should be posted in the Arduboat user group.  I have a boat, not a rover, and forget how I came across your post here.

      Regards,

      David R. Boulanger 

    • Thank you for the information. I will definitely post in the boat group next time.

      Now, I've got the boat back on the bench and I seem to be having a strange issue. To be completely sure I've got everything on track, I removed my reversals in the radio. I did perform your bench test, and it was in-fact turning the boat the wrong way in Steering mode. So, I reversed the "Roll" in Mission Planner, re-ran the test, and it seems to be working properly. And to be completely sure, I even planned a mission, set the boat to Auto...then manually pivoted again to make sure it was trying to go the right direction, which it did. So, success on the software side I believe.

      My only issue is that in Manual mode, my control is still reversed. It doesn't make much sense as no matter which direction I reverse in Mission Planner, the radio still steers backwards when in Manual. So, my question is...can I reverse again in the radio, while leaving my current and correct reverse settings in Mission Planner, without messing anything up?

    • Developer

      Yes, you will need to reverse on your radio as well.  Think of it like this.  When in an autonomous mode like AUTO the autopilot needs to know which way to move the servo to steer the boat - that's what the RC?_REV tell's it.  However, in Manual mode its straight pass through, the autopilot isn't doing anything and RC?_REV isn't used so you need to set it to work the correct way in your transmitter - hence the need to  reverse it in your transmitter.

      Just make sure you test the manual "nudging" in auto mode so when its in AUTO and you want to steer it to correct its path when you move the stick it turns the boat in the correct way.

      Thanks, Grant.

    • I had no idea you could "nudge" in Auto.  I learn something new everyday.

      Regards,

      David R. Boulanger

    • Understood. I reversed the settings in the radio, re-tested, and everything looks good to go throughout Manual, Steering and Auto modes. We're going to give it another shot Monday to see how it's working now.

      If we still have the issues as far as initializing, arming, etc, I will report back with logs and photos. 

      Thanks again for everyone's help! Hope everyone has a great weekend!

  • Have you tried reversing the rudder servo in your parameters.  The fact that you can learn a mission tells me your GPS is O.K..  Like Tom said, pictures, parameters and a log would be useful.  This could be that you reversed rudder direction in your transmitter instead of in your Pixhawk.  There can be problems with reflectivity off the water but I don't think this is your problem.  Does Steering mode work?  That would rule out the GPS and focus on your parameters and compass.

    Regards,

    David R. Boulanger

    • Admin

      Hi David,

      Good points.

      To reiterate, reversing the Transmitter steering channel should be done to correct the steering direction in the Manual Mode only.

      However, if the vehicle goes in circles in the Auto Mode, then the "check box" by the roll bar in the Radio Calibration screen should be checked to correct the steering direction.

      Regards,

      Tom C AVD

  • Hi,

    One think very important in boat configuration, you need to start the system on shore or if is it impossible, you need to disable the gyro autocalibration at startup.

    Because in water, the boat alway moving and the gyro is not able to make a good calibration.

    Regards,

  • Admin

    @tjfhlv,

    First off, word descriptions are a good start, but pictures and tlogs and dataflash logs are worth a thousand words.

    So, could you please provide some pictures of your boat so we can get an idea of your physical configuration.

    Then, could you please provide tlogs and dataflash logs where the boat is in the water and where it is out of the water to help troubleshoot your issue.

    Also, you might want to move your post to the ArduBoat User Group.

    Regards,

    TCIII AVD

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