DJI Naza-M V2

[JezUK1]

Posted on behalf a friend.

Having just installed the naza flight controller in my 450 (modified alien style frame), I set it up with no obvious problems. Ran both basic and advanced calibrations, calibrated the controller and set the various options as I prefer them. I set it up for Atti mode / Manual mode on the flap switch, opting for Atti mode for testing till more used to the characteristics of the controller.

Given it was night time, I decided to give the quad a quick hover in the house to see it was running ok, having done all the various tests with the motors off to see motors were all starting up simultaneously, and were changing speed in the expected fashion etc.

All was fine for about 30-40 seconds, with a calm and gentle stable hover that I was extremely happy with. I decided to do a couple of yaw turns to test it was yawing smoothly, which it appeared to do fine about 10 times back and forth, when absolutely randomly with no change of input from me, it decided to put full power through the motors, bouncing off the ceiling and coming to a crashing halt on the floor. Shocked wasn't quite the word! Thankfully there was no damage bar four pointed marks in the ceiling, but I was decidedly nervous after this as you can imagine.

I left it till this morning and reinstalled the firmware on the controller and pmu, went through every setting with a fine tooth comb including all calibrations. Everything is apparently fine. Did all the tests with the props off, making sure to do a series of yaw movements to see if it triggered a full throttle event, but it didn't. I finally plucked up the courage and attached it with a rope to a 10kg weight in the garden with about 6 feet of slack so it couldn't take off for the heavens. Five heavy bumps from 6 feet on the end of a rope later, with calibrations and pissing about between each attempt, and I've finally broken an arm on the quad as well as my patience for what appears to be a very expensive and dangerous piece of junk!

This isn't my first quad, nor my first flight controller, but I can genuinely say that it's the first time the behaviour of a flight controller has ever frightened me! To be flying in such a stable fashion and then within a minute of taking off decide to randomly gun the throttle to full power is pretty unbelievable!

Just to confirm, I started with the recommend settings for the f450 (very very similar to my quad) found on page 8 of the quick start guide. Lowered and raised the vertical and yaw gains a touch to see if that would change the behaviour but to no avail. The quad is also pretty close to balance, all four carbon fibre props were fully balanced (at least before hitting the ceiling and garden grass half a dozen times) and I could stick one of my other flight controllers in it and fly right off with no problems at all. It was flying temporarily on a cheap KK2.0 for testing with no issues before I decided to bite the bullet and go for what I hoped would be the better quality naza.

Has anyone got any suggestions that might explain this, beyond what I suspect... that there's some form of fault with the electronics making it randomly power up in response to an erroneous input from a sensor?

Do you think it's a matter of returning as faulty?

[stef1]

did it go into failsafe and try to get to 20m to do the auto land?

[FPVSimon]

What type of Tx and Rx for control?  If 2.4gHz then is there a wifi router in the house?

It does sound to me like it went into RTH.

[JezUK1]

I'm not convinced it's an issue with wiring. It was also flying on a KK2.0 board with only the connectors pulled out from the ESCs and reordered (KK2.0 has a different motor order), and the DJI cables swapped in to link the naza to the Rx unit because I liked the fact they were neater (shorter) than the cables I'd used previously.

As for Tx and Rx, I'm using a JR Propo XG6. All channels are checking out correctly as calibrated, and I've altered the two position switch so that it hits Atti and Manual, so it's not being accidentally put into failsafe (which shouldn't result in a full power being dumped to the motors, even if it was).

I would assume that RTH would only be possible if GPS was connected, but I'm running without it. If it is doing RTH with no GPS, that's frankly even more worrying!

Everything is behaving completely normally and flying beautifully right up until the explosion of action, generally it seems after some yaw movements, but that may just be I've been doing yaw movements to try and make it happen and then it randomly happens for another reason, leading me to believe it's doing it on yaw movements. It's perfectly stable yawing for quite a few turns as well, so it might not be that being the cause?

As for the wifi there is wifi in the house where I did the initial test when it hit the ceiling, but I live out in the country and have a fairly large garden area where I took it to check with it tied down, well away from the house, and it was still doing it repeatedly despite the fact the wifi signal at that distance will at very least be incredibly insignificant (I couldn't possibly connect with a laptop or phone).

[FPVSimon]

The RTH without a GPS will just land where it is so there would be a decrease in power.

It does sound as though it might be the Naza. Is there someone near you that has one you can borrow to check it is that?  The only other possibility could be you Tx giving strange commands.

[JezUK1]

LFor got to say regarding wifi.
There is wifi in the house where I did the initial test when it hit the ceiling, but I live out in the country and have a fairly large garden area where I took it to check with it tied down, well away from the house, and it was still doing it repeatedly despite the fact the wifi signal at that distance will at very least be incredibly insignificant (I couldn't possibly connect with a laptop or phone).

I had a bit of time this afternoon, so decided just to bite the bullet and strip down the quad to let you see the wiring.

1. This shows the quad as it would fly, aside from the battery connectors being disconnected obviously. I replaced the broken arm last night (front left - you can see I had to use different screws because the only arm I had was a different thread), so the quad can be tested if need be.

2. Removing the battery, battery strap and removing two cable ties which hold the pmu and led module in place.

3. PMU has to be unplugged from naza in order to allow removal of the top plate. Also removed the small telemetry transmitter.

4. Disconnected the LED module, removed the top plate, pulled the Rx through the top plate, and then reconnected the LED module again.

5. Reconnected the PMU to show how it was connected before the top plate was removed.

6. Close up showing the connections between the Rx and naza. I've removed the LED module and PMU cables for clarity.

7. Unbundled the ESC cables to try and show they're going to the correct ESCs. Hard to show. You'll see underneath a square taped up power distribution board. Power comes in from the battery connector and goes out to a 4 way cable for the ESC power and also out to the PMU.

If its of any help here are some pics of the setup.

[FPVSimon]

If, as you say, all motors increase to full power together then the problem is not related to motors or ESC's (more likely to be just one if it was).

It has to lie with either the JR Tx, Rx or Naza.  If you can swap the Tx and Rx with others, I would suggest that as a start.

[flybywire]

All of the above, I would get rid of the props, at least that way you'll do yourself no harm.  The only foibles I know of with the Naza (v1) is the sensors get stuck, and require a sharp tap underneath with a screwdriver, and the light
Hitting the barometer, but can't see that can be relevant here.  Swapping out is probably your best option here. Try the tap first though!

[JezUK1]

Good news (or at least tentatively good news if the quad continues with good behaviour).

I was fiddling about with the software trying to figure out anything that could be causing this, and I had a notion to click "Restore default settings". Took a picture of the settings pages with my phone and then hit the button. I then went through and redid all the settings as they had been, and redid both the basic and advanced calibration. The advanced calibration behaved quite differently, taking significantly longer than before and then a box coming up asking me to switch the quad power off for 10 minutes and then switch it on again. I gave it a good 12-13 to be on the safe side and then switched it on. It ran the calibration bar up for a short period then confirmed calibration ok. I wasn't convinced so re-ran it. After around 7 minutes or so (I'm convinced longer than the advanced calibration took previously when I was having problems), it confirmed calibration ok.

With a sense of trepidation I went out to the garden, which was concerningly quite a bit more windy than it had been, and hitched up the weight and rope (with an additional smaller weight further up the rope this time to act as a damper should the worst happen again). Took off and the quad was like another animal compared to previously. Before it had been roughly as smooth as the KK2.0 board I previously used (and had hoped to improve upon) with a slighly more aggressive throttle response, right up till going crazy, but having done this reset/recalibration, it's super smooth even in the wind. Flew right through two 3s batteries and then got brave and stuck a 4s in it and flew right through it too. That's about 20-25 mins of flying (the quad is running very light because I'm risking the minimum gear on it till I trust it) and zero problems. If it can do 10 flights on the rope as good as that, I'll trust it off the rope and see how things go.

In summary, if you get this again with another customer, ask how long the advanced calibration is taking. If it seems about 3 mins or so, that probably indicates there's a problem (I just assumed that the indication of 5-10 mins was playing safe on dji's part). Also ask if the throttle response seems a bit aggressive, because I realise in hindsight that it was aggressive even when it was flying normally (I didn't have previous naza experience to go on). And lastly recommend a reset, redo all settings and recalibrate, making sure the advanced calibration takes the expected 5-10 mins.

Thanks for your help all and with a bit of luck I'll not be back in touch regarding it lol.

[flybywire]

Excellent!  Sounds like you can now enjoy the 'chilled out' flight experience that DJI hardware gives you.  Well done. THinking back to the 'big' Naza upgrade a few months ago, it did introduce the qyro calibration test on first install, and that did take more than 5-6 mins, I remember as I did the calibration with the quad in a springy wooden floor, and didn't dare move until it quit!