Strange fly away with Cinestar 8, DJI A2 and Movi M5

Discussion in 'MōVI MR' started by Claudio Carvajal, Aug 28, 2014.

  1. Claudio Carvajal

    Claudio Carvajal New Member

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    We had a strange fly away and crash a couple of days ago with our Cinestar just after lift off.
    I had been tuning the Movi MR with the copter suspended between two chairs. Just before we started up the Cinestar it was rotating a couple of turns due to the Movi being on. Then I turned the Movi off with the kill switch on the remote. On the first attempt to lift off, it tipped to the side. On the second attempt it drifted very hard to the side without our operator being able to control the copter and it crashed against an antenna on the roof of a house. Luckily the repairs will only be a couple of hundred bucks. The Movi was off during the crash so it seems that it didn't suffer any damage.

    Now my question is, do you think this had to do with the copter rotating around on the ground and that the compass/IMU of the A2 got disoriented because of that? We have the Movi attached to the frame with the Toad In The Hole. Any one else suffering from this?

    We are thinking of trying to reproduce this in a more open space, and try to make it go to fail safe when this happen. But it is a little bit scary to have an expensive gimbal attached underneath when doing this.
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    If your MōVI was in dual operator ("Airborne") mode, you should be able to lock it on takeoff so it doesn't spin. Did you not do that? Or are you flying in handheld mode?

    Has your copter flown successfully without the gimbal and with some weight attached to simulate it? I'd also strongly suggest you not fly it again (assuming it's even still flyable) until you've tethered it tightly to the ground and confirmed all its systems are working properly.
     
  3. Gary Haynes

    Gary Haynes Administrator
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    Loose prop, motor vertical alignment?
     
  4. Jason Smoker

    Jason Smoker Active Member

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    Sorry for you crash!

    I wonder if the signals tx heli and tx m5 are getting mix being to close together maybe?

    Flying near houses etc you also have carefull of the antennas/magnetic fields can cause serious headaches.
     
  5. Claudio Carvajal

    Claudio Carvajal New Member

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    Thanks for your replies!
    We have a Futaba T14SG for the Cinestar and a Spektrum DX8 for the Movi. You think the frequencies of both TX can be mixed up?
    I tightened all the props and motor mounts before the take of and the particular crash. We had been flying earlier the same day on the same spot without problems.

    We flied in Airborne mode and the Cinestar started to spin around on the ground a couple of turns before I hit the kill switch on the TX. My idea was to turn the Movi on with the switch once it was airborne, but I didn't even have a chance to do it before the copter started to drift heavily and crashed. I'm aware that you also have the possibility to lock the Movi with the TX too, and we will be practicing this before take off from now on.
     
  6. Sam Slape

    Sam Slape Member

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    How is the IMU mounted? Could it have been knocked and not level?
     
  7. Jason Smoker

    Jason Smoker Active Member

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    Sounds like something is wrong the m5 set-up or the m5 itself. It shouldnt spin if the switch is on a 3 three way switch in the centre it should lock like steve said!
     
  8. Ryan McMaster

    Ryan McMaster Active Member

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    The Movi Mode is VERY important. Airborn also adds some compensation for a few things not offered in handheld mode that kotpers do when it comes to movement. Steve is right on the money here.

    On the A2 note. I had a VERY odd thing happen the other day with my MK HL hex that sounds similar to this due to a bad GPS signal. I don't know DJI too well , but what happened was on takeoff I was planning on going straight up as the shoot involved a Nadir survey (5 cameras in a mount, experimental). As such once I was 5m off the ground I swapped to GPS HOLD and the kopter started to fly NW very hard. Switched out and heard my radio say GPS FIX LOST. So not wanting to risk it I brought it back in manual and put it in alt hold and did some tests.

    I was getting a BAD GPS signal for about 5 minutes (My phone also was showing I was 200 ft away from where I was). Every time I would go to GPS it would fly NW at the same heading and speed, some "Default Location" that the GPS unit goes to. I checked for satellite issues and any recent solar flares, none.

    Here is a GPX from another test that day sans gimbal. It should show the kopter ONLY above newlands park (where I was testing) but it shows it all over the area.
     

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  9. Brad Meier

    Brad Meier Active Member
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    When he is in dual mode, it will spin when on the ground. Completely normal and that's why there is an airborne locked mode.

    The spinning could've also confused the A2 IMU, but I'm no DJI expert.
     
  10. Ryan McMaster

    Ryan McMaster Active Member

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    After reading into the issue a bit more, and one of my colleagues taking the code from 3dr apart I think we found a lead on the problem.

    We have a 3dr Y at the uni that did a random flyaway, into a wall destroying it. Looking at the GPX files there was no indication of why. Upon looking at the code that runs the kopter we found that there are few internal self checks on the math and algorithms that control the self stabilization in GPS and out of GPS mode. These self checks are present in MK and a few other systems (how do we know? When I lost the first octo to I2C fail it tried to restart and reboot to save itself) and provide a level of redundancy that does not exist in 3DR. I would hazard a guess that due to the similarity of the flyaway issue, DJI is the same. I would think the lack of self-checks are killing the input control system (Rx IN) and the GPS memory/default setting and could ALSO be killing motors too (or giving them an improper throttle read). The self checks are the math proving to itself that it works and can solve out and, if it hits a fault can re-start and resolve with out issue. I am not a CS by any means but the CS guys I work with seem to think this is the issue and we are working on nailing it down right now. We just bought a DJI system and are going to pull the code from it and see if we are right before we even fly it as that 3DR Y just put a huge dent in the project.

    The code is robust enough to work 99% of the time, but that 1% where the lack of a self check on a critical system is the real kicker. When it fails it fails hard.
     
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  11. Claudio Carvajal

    Claudio Carvajal New Member

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    After repairing the broken booms, broken motors and replacing all props, we have been flying again succsecfully without crashing. We now always use the "airborne lock mode" before take off, and when we forget to switch to that mode (and the copter spins), we cycle the transmitter and battery (restarting the IMU) and we haven't have the same problem since. We can be kind of certain that it was the spinning that made the A2 IMU/compass/gps to loose orientation and made the copter drift heavily to the side after lift off.
     
  12. Tuukka Ylonen

    Tuukka Ylonen Member

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    Even when in airborne mode, my Movi M5 starts spinning every now and then when switched from off mode into "locked" mode. And I´ve heard others have had this issue too. So "locked" mode is not 100% trustworthy.
     
  13. Dylan Glockler

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    I'd just like to clarify as I prepare to fly my m5 on a modified s1000 for the first time. This mode everyone keeps referring to as 'airborne' and 'dual operator' - is the same as 'remote' as indicated on my FreeflySystems provided Spektrum DX7S remote? I

    t's a three-way toggle switch with REMOTE | MAJESTIC | OFF.

    I found the answer in the latest version of the manual - have to set airbone mode:

    Gimbal Application - Configures the gimbal for either Handheld or Airborne use. In Handheld use, the center position of the Dual Operator Mode Switch enables Pan Majestic operation. In Airborne use, the center position of the Dual Operator Mode Switch parks the gimbal for takeoff and landing.
     
  14. Jason Smoker

    Jason Smoker Active Member

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    yes dylan you are correct in airborne mode its the same switch. put into majestic mode for airborne It will lock the pan so you can take-off with out the heli spinning and put same when you land.
     
  15. Chris Jordan

    Chris Jordan Member

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    BE careful. SO many guys have burned up motors on the S1000 putting an M5 under it. It's way over spec.
     

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