NAZA detecting aileron input at zero trim?

[mrbonk]

Hey folks,
We've recently got an F450 with a NAZA M controller to experiment with GPS position hold, but I'm coming up against a strange issue. About 50% of the time, the controller boots up and detects a small amount of right aileron input, which is resulting in a drift to the right. If I land, reboot the unit and go again, all is well and it's solid as a rock. Has anyone else had this happen?

In the assistant software, this is easy to see, even after performing a calibration with all subtrims and tx trims set to zero. I can calibrate it, it says the aileron is set correctly, however when I reboot the unit, sometimes it shows a small amount of right aileron input. If I reboot it and connect it again, it's back in the center again

I know it's not the transmitter pot, because I have other equipment that uses visual representation of the tx output and it's perfect in there.
I know it's not the receiver, because it came out of an EDF jet that was flying perfectly right before I removed it to fly the F450. I've also briefly tried another receiver and got exactly the same results.
I know it's not CG, because I've gone so far as balancing it on 2 sharp points and using a builder's spirit level before doing some test flights.
My props are APC E props and are both blade and hub balanced using a Dubro balancer, so it's not vibes. We've got a GoPro stuck directly to the bottom of the frame and have virtually zero jello, even in 60FPS in full sunlight, so it's about as good as it gets without tape balancing the motors with a spectrum analyser (which I *am* going to do eventually anyway).

But all of those things are redundant anyway, because if I reboot the unit and fly again, it locks absolutely perfectly and does not drift.

I've done a search on here and it seems a lot of people have experienced a drift to the right, but everyone seems to have just been happy to either tilt the MC when they mount it, or just put some trim in to counter it. I'd rather not do either, because half the time it flies and locks position perfectly!

 

[Tomstoy2]

I don't have a Naza, but I do have a WKM.

As I understand things, when calibrating with assistant, it is imperative to have the controller perfectly level. I use a very accurate bubble level, ( only cost $8, ), to level out the controller before calibrating.
After you write, that is the figure you have stored.

On the ground, after calibration, The controller does not care that much about how level it is, as the gyros are not stabilized.
So, once in the air, out of ground effect the controller will keep the acft level to its stored position.

With that in mind, what it sounds like to me is that your initial calibration, when written might be just slightly off, even though it displays green in assistant.

One thing to keep in mind, when you mounted the Naza to the airframe, a trapped air bubble under the mounting tape is enough to affect the level. If you are positive that you do not have a trapped air bubble, then check with the level that the airframe is level, then that the Naza is level.

All the arms should be at the same plane with each other, too.
To check this, if you have a true flat surface, like a glass table, turn the acft upside down and verify that all the motors touch the glass. Shine a flashlight behind the motor shaft on the glass and see if you get light between the shaft and the glass.
If one is slightly off, you can try bending the arm a little, thus forcing the cf plates to give a little to get it to sit on the glass like the rest of the others.

Try what is suggest and see if she behaves better.
If that doesn't do the trick, then I would think a gyro is an issue.
You can then try plugging in the battery, allowing everything to boot up and then unplug and re-plug the battery back in and see if the problem is gone.
If it flys right then, you either incorporate that into your pre-flight sequence or contact your dealer for a replacement.
If you do contact your dealer, give him all the info of your troubleshooting. If he gives you grief, there isn't much you can do, but at least you know then that he isn't who you want to do business with in the future.

Most of the problems you will encounter will be self induced, however.

 

[mrbonk]

Thanks for the tips (all of which have already been done previously), but I can replicate this behaviour in the assistant software itself. Sometimes, I can boot the unit up (having made sure it's level), perform a tx stick calibration and be left with the aileron channel reading slightly to the right (and black). If I reboot the unit and perform the calibration again, without moving it, I get all greens. It appears as if the unit is incorrectly calculating the mid point of that channel after the process is performed. Maybe something is happening when the power is connected that's causing a momentary issue with the firmware??

Either way, I think I'm just going to contact DJI directly and ask them about it. I just didn't want to do that until I was sure I'd done everything correctly.

 

[OneStopRC]

I did not see you mention the radio type, but I wonder if you have a sub-trim going on or some weird mix? is your radio set to Acrobatic or airplane mode?

 

[mrbonk]

I did not see you mention the radio type, but I wonder if you have a sub-trim going on or some weird mix? is your radio set to Acrobatic or airplane mode?

It's a JR 11X. No subtrims and no mixes that interact with aileron at all. I use this radio with all my other models (except my slopies.....I use a disposable DX6i for those) and don't have problems with aileron control at all, so I know the radio is fine.

I did some more testing today. If I plug the unit in and fly as soon as it has GPS lock, it drifts to the right. If I plug it in, let it lock, then reboot it, all is well. Very odd indeed!

 

[OneStopRC]

Dumb question here.... now this only does this while in GPS, Declination is not possibly at fault here is it? I know you said in the software you're seeing this weird issue.... so maybe I am barking up the wrong tree?

 

[mrbonk]

Dumb question here.... now this only does this while in GPS, Declination is not possibly at fault here is it? I know you said in the software you're seeing this weird issue.... so maybe I am barking up the wrong tree?

Actually, it doesn't seem to matter which mode it's in, although obviously it's more noticeable in position hold mode because you *expect* it to stay put, rather than drift with the wind.

At least I have an interim solution that appears to work for now. I'll just go through the power cycle twice before I fly, while I'm waiting for DJI to get back to me and let me know what it might be.

 

[OneStopRC]

Here is one thing I noticed with mine, weird but this is what happened with me.....

I had some trim on one of the sticks, not sure which. Anyway, in the assistant it was well over center and the only way to fix it was like this.. I think it was like this. Save your settings with the trim on the radio to bring you into the center. Remove power to the Naza, set the trim on your radio back to zero. Go back in and calibrate your sticks again, save, power down the naza and radio, fire up your radio and naza. See if that helps.

 

[mrbonk]

Yeah I've already been through experimenting with trims during calibration. Didn't change a thing. Originally, I tried using trims etc when I noticed that the aileron channel wouldn't return to center after calibration, but then I noticed in the manual that it says to just click finish anyway, then reboot the unit. Hey presto, center reading after reboot.