IRIS+ Fail, Flew Away and Crash

Posted by Quauhtli Noel Martínez Zazueta on December 15, 2014 at 7:59pm

Hello everyone:

Yesterday, what it seemed like a nice day to fly, it became the end to my IRIS+. I just started flying over a wheat field and suddenly the IRIS+ stopped responding telemetry commands, raised up itselft for about 50 meters, then flew away and went side until it crashed, like if a motor had stopped working.

The results: all the four legs got crashed, the chasis is all with scratches, the front red leds didn't turn on anymore and the GoPro Hero3+ housing scratches too. Fortunately the Gimbal was not installed.

I'm feeling pretty dissapointed now on the IRIS+ since I spent so much money on it. Today sent an email to Help department at 3DRobotics hoping for an explanation of what happened and looking forward for some kind of warranty.

Here is the video and the photo showing how the IRIS+ ended up so I wondering if you guys could notice something wrong on this attempt to fly.

Thanks!

Log files: https://www.dropbox.com/s/1nzuiixs0lba4ju/QUADROTOR.zip?dl=0

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Replies

    • Developer
      Craig Elder > DG December 24, 2014 at 1:00pm

      Compass learn works very well on airplanes but not so well with multirotors.  Best to leave it off and perform a proper compass calibration.  Doing compass motor  learning http://copter.ardupilot.com/wiki/arducopter-parameters/#Motor_inter... can be very helpful

    • Rob Dunbar > DG December 20, 2014 at 8:39am

      I determine level take off when in stabilized mode, hover then center the sticks. If the craft doesn't float away to fast then I consider it leveled. If it floats away in one direction I power it off and find a level place to try again.

      GPS signals are so weak and the gps radios have to be so sensitive just to receive the signal it's easy to swamp them with other rf.

    • DG > Rob Dunbar December 20, 2014 at 10:27am

      That's pretty much what I do; have never taken off in Loiter.

      I'm hoping for a response from Joe Dietrich on why he sets COMPASS_LEARN to 1. I have never questioned why it is disabled.

    • Joe Dietrich > DG December 20, 2014 at 5:46pm

      From the description for COMPASS_LEARN = "1", it states that it will automatically determine the OFFSETS for the compass (to the flight controller, I assume).

      It is probably similar to the offsets you MANUALLY enter into NAZA V2 to identify the X, Y, and Z axis differences between the GPS Puck and the Flight Controller.

      I noticed the first time I did a calibration for the Pix where you rotate the bird around all three axes, you could see the settings creating OFFSETS.  Somehow, the Pix figures out (maybe improves) the OFFSETs each time you fly or start-up.  That's the only reason I can figure you would want to set it to "1" vs. "0".

      Are you using the 3DR uBlox GPS with Compass?  Mine seems rock solid, I can put it into a yaw spin in either direction, and it just about spins like a top.  Now I can say on my early start-up flights, the yaw spin wasn't as tight, but as I flew more, it definitely seemed to get better.  I know on NAZA, if you don't have your offsets right, the bird won't spin like a top.  I've had to help several people fix their NAZA offsets, and they saw really good improvements.

      I agree the GPS HDOP is definitely a PITA when trying to get a lock for Pre-Arm.  HDOP stands for High Dilution of Precision, and from the Wiki on it, "When visible navigation satellites are close together in the sky, the geometry is said to be weak and the DOP value is high; when far apart, the geometry is strong and the DOP value is low."  So I guess we see why having 10 - 13 satellites if they're close together doesn't help the F/C.

      Here's what you can do though, usually HDOP will get better over time (as satellites move).  If you're not planning on flying in GPS based mode, such as LOITER Mode or AUTO (Nav using GPS), set your GPS_HDOP_GOOD setting at 250 to 350, at least you'll get past the GPS Pre-Arm check.  Keep in mind that RTL (Return to Land) might not work so well though! However, as your M/R moves around, the HDOP will change (and will usually get better).

  • David Jackson December 19, 2014 at 9:58am

    First of all why does the Pixhawk allow tack off without a good GPS and or not level, if this will result in a possible crash.

    Second, I had a similar experience with a Pixhawk  hovering a short  while switching to Loiter mode then just veering off to the side. I was able to recover by switching to Stable mode. After examining I found that the last time I made a change I inadvertently mounted the compass 90° off. Correcting this solved the problem. 

    To be clear with the compass 90° off the Pixhawk complained about compass not calibrated and accelerometer not calibrated and it took a few time to get every thing recalibrated in the compasse off configuration. So the Pixhawk detected something had changed and needed to be recalibrated. If a compass that is calibrated know where North is and certainly GPS knows North, why if there is a descripancy does the Pixhawk allow this configuration to fly.

  • Quauhtli Noel Martínez Zazueta December 18, 2014 at 10:25am

    Thank everyone for your interesting opinions and diagnosis. 

    Just to let you know that I've got an answer from 3DR Support. They said, as many here, that I tried to took off on a non-flat surface which I did. Logs registers a big difference between the EKF1 Yaw and the actual IRIS+ Yaw, so that procuded the crash. They offered me two alternatives: 15% off on replace parts or free-revision-repair if I sent the IRIS to them (I will pay shipping handling), which I'm going to do. Thank you all and fly safe, never do what I did.

    • Richard Kennedy > Quauhtli Noel Martínez Zazueta December 18, 2014 at 10:29am

      That's great you now know what happened that makes you much more confident to fly again! Great customer service too!!

  • Richard Kennedy December 18, 2014 at 10:15am

    Bummer about your crash!!! If there is any bright side you found it. I've been flying for about  year and one three things I have learned to do. Start the pixhawk on level surface and don't touch it until it's done booting up. Wait for it to get at least 8-9 sats and an hdop of under 2. And most importantly make sure to learn how to fly in Stab mode and have that mode available at an instant notice! Always when it doubt hit stab and high throttle. This way you are not relying on the gps in any way and you can gain altitude THEN figure out what's going on and or fly home. That's not to say that would have helped in your case I have no idea. But it has saved me a couple times.

    The video reminds me of when I had a fly away and it was because I didn't know I had broken off my TX antenna so as soon as it went out of range it just kept going with the last know stick posositions. Your quad looks like it had a slight right stick and it just kept going with no more changes, Just like it lost TX signal. I set up throttle FS after my issue. Anyway good luck putting it back together!! 

  • Ray Gamero December 17, 2014 at 2:10pm

    I'm confused with your logs.  In all of your logs, they bank is around 45 degrees. It also had GPS problems continuously.  

    Quadcopters should take off very level.  If it doesn't take off level, I land and try to diagnose the problem.  I often re-calibrate accelerometer and/or the compass. 

    I'm surprised you didn't notice the bank problems when you had it hooked up to mission planner.

    Before I fly a new configuration (nearly every flight, for that matter).  I look at the autopilot attitude to make sure it knows which way is up.  

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