[SOLVED!!!] - IMU ACC1 shows "Data Error" - AC has never suffered a crash or anything similar.

[Deleted member 94047]

I had flown the MA this morning, in smart capture mode without the remote or phone even. No issues (well it refused to land at the end and only landed after it's battery reached critical - but I think that was just landing protection being picky).

I come home review the footage, and decide to change some of my camera settings. I power on the MA from a freshly charges battery and it tells me the Vision System needs to be recalibrated. OK, it was doing just fine this morning; but I tell myself better do what the app says anyway. I fire up Assistant 2 and I do the requested calibration. Took me two tries but it was successful. The MA was sitting right next to my Surface Pro and I say "let's see how the magnets on this thing get along with the MA's compass". I enter into the "sensors state" setting and there it was - ACC1 Data Error!

What the *#&! When did that happen? How did it happen? I tried a IMU calibration, on a level surface; IMU calibration completd successfully. I restarted the MA and the ACC1 Data Error was still there. I did another IMU calibration, restart the MA - it is still showing.

So question, what could have caused this and how do I fix it? Any help is greatly appreciated. TIA!

 

[BigAl07]

You may have a look at this thread:

Mavic Air IMU Acellerometer Data Error ACC0 ACC1

Is it time to replace the Mavic Air IMU module with these errs? I hit the leaves and it fell down to the ground. Thanks.

mavicpilots.com

 

[Deleted member 94047]

You may have a look at this thread:

Thanks BigAl; greatly appreciated! That is exactly the kind of info I was looking for. Being where I am, I can't send the MA o DJI nor do I have another repair option. I was searching all afternoon yesterday on this site and else where I don't know how I missed that. Perhaps it is time to open up this baby

 

[Deleted member 94047]

So after reading through the thread which BigAl linked in post #2 above and watching a few Mavic Air tear-down videos on YT, I am going to have a go at opening mine too see if resetting the IMU ribbon cable can fix this error. But before I go ahead and do that, I would love to hear from people in the know regarding:

(1) Is it perhaps better to leave it as is - with just one functioning accelerometer? There are no other errors other than the data error on one of the accelerometers and IMU state shows "Normal" on the system status page that appears immediately after I tap GO FLY. So should I open it up OR should I just leave it be? (Note - I have a mild case of essential tremor on both hands and do struggle with delicate tasks. I am really not looking forward to opening up the MA if I can help it, but if I have to, I will).

(2) If I have to open up the MA - where exactly is the IMU ribbon cable located? I can see the IMU module is located on the underside of the main board (the black, box like housing you see in the pics below) but I can't see where the ribbon cable is from the pictures I have found so far. If any one has experience doing this or a better picture, I would greatly appreciate any pointers.

Many thanks in advance.


P.S> Please note that sending the AC to DJI or a repair shop are not options I have owing to my current location.
And I wish those of you who celebrate Christmas and New Year this time of year a very joyous holiday and a very happy new year!

 

[lannes]

Before you do surgery, have you refreshed the firmware via DJI Assistant 2 one last time and done a factory reset ?

Have you recently upgraded ?
Maybe a downgrade might fix it

 

[Deleted member 94047]

Before you do surgery, have you refreshed the firmware via DJI Assistant 2 one last time and done a factory reset ?

Have you recently upgraded ?
Maybe a downgrade might fix it

I have not done any of that thinking this is most likely a hardware issue. But hey, it won't hurt to try, at least there is no downside to it. Thanks for the reminder, I will do that.

 

[Deleted member 94047]

As an update to the above, I did a factory reset followed by a firmware refresh. ACC1 still shows a "Data Error". The MA was already on firmware v .0620, so downgrading was not an option. I am still hoping to hear from people on the risk of flying with just one working accelerometer before I open it up.

Calling all the experts! @BudWalker, @sar104, @Meta4, @brett8883 - I understand this is a question that may not have a clear cut answer, but I would really appreciate your opinions on this matter. Are the two accelerometers there as a matter of redundancy or does the AC actually need both to fly properly? What is the likely impact of flying with just one functioning accelerometer on the over all flight performance of the AC? Thanks in advance for any answers.

 

[lannes]

Does the error show up when the AC is hovering ?

 

[Deleted member 94047]

Does the error show up when the AC is hovering ?

Haven't checked that; I simply assumed the error will still be there when the AC is in a hover or flying. Will test and report. Thanks.

Update: Error shows up when AC is hovering

 

[BudWalker]

As an update to the above, I did a factory reset followed by a firmware refresh. ACC1 still shows a "Data Error". The MA was already on firmware v .0620, so downgrading was not an option. I am still hoping to hear from people on the risk of flying with just one working accelerometer before I open it up.

Calling all the experts! @BudWalker, @sar104, @Meta4, @brett8883 - I understand this is a question that may not have a clear cut answer, but I would really appreciate your opinions on this matter. Are the two accelerometers there as a matter of redundancy or does the AC actually need both to fly properly? What is the likely impact of flying with just one functioning accelerometer on the over all flight performance of the AC? Thanks in advance for any answers.

AFAIK just one IMU will be used. But, the FC may want to switch from IMU(0) to IMU(1) during flight or it may want to start with IMU(1). It's unknown, to me at least, if the FC is smart enough to know not to start with IMU(1) or switch to it.

Have you tried removing the props and attempting to start the motors?

 

[Deleted member 94047]

AFAIK just one IMU will be used. But, the FC may want to switch from IMU(0) to IMU(1) during flight or it may want to start with IMU(1). It's unknown, to me at least, if the FC is smart enough to know not to start with IMU(1) or switch to it.

Have you tried removing the props and attempting to start the motors?

Thanks for dropping by @BudWalker; The motors start fine and I just did a very brief hover test outside as well. Apart from it asking me to re-calibrate the compass, AC seemed to perform fine. But like I said, it was a rather brief hover test. I have attached the DAT file just in case you want to have a look at it. Thanks again!

 

[BudWalker]

Thanks for dropping by @BudWalker; The motors start fine and I just did a very brief hover test outside as well. Apart from it asking me to re-calibrate the compass, AC seemed to perform fine. But like I said, it was a rather brief hover test. I have attached the DAT file just in case you want to have a look at it. Thanks again!

The IMU(1) data is almost identical to the IMU(0) data. Here is the accelX from both IMUs

The accelY and accelZ are also almost identical.

From the eventLog stream we have
-158.136 : 0 [L-SENSOR]imu group0 ok
but nothing said about IMU(1).

I looked at a .DAT you previously submitted for your MA. It also mentions that IMU(0) is OK with no mention of IMU(1)'s status. So it would seem that a lack of IMU(1)'s status is not significant.

 

[Deleted member 94047]

Awesome! Thank you so much @BudWalker, really appreciate the help. OK, I will put the dissection on hold and give it a good spin in an open field tomorrow and see how it performs. Still baffled as to what could have caused the error in the accelerometer but if I can still fly it, I don't mind it remaining a mystery

 

[lannes]

A few people have hit the Air's to fix IMU issues LOL

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[Deleted member 94047]

Here is what I see when I hook the MA to the old DJI Assistant (with debug enabled)


The Accelerometer on IMU 2 seems to be stuck on the X axis; no matter how I move the AC, it stays at that value of 16.0***. The readings on the other two axes are close to those from IMU 1. Now, I have no idea what this means or if it is a good or bad news. Again, I call on the experts for help. @brett8883 - you are the ultimate expert on Assistant 2, can you tell me how to calibrate the IMU using the Assistant rather than the app? @BudWalker & @sar104 - any thoughts on what this means? Again, many thanks in advance for your help.

In the meantime, I am heading out to do a through flight test.

Edit: And I think i know what caused this. In one of my bike rides last week, I didn't want to carry a backpack and rode with the MA hanging from the handlebar; it was in the small soft case that comes with it but I guess that was not enough to dampen the vibrations and jolting from the bike. Don't do this folks!

 

[Deleted member 94047]

A few people have hit the Air's to fix IMU issues LOL

You mean i should give it a good old fashioned whack? I thought that method only worked with old TVs.

 

[lannes]

You mean i should give it a good old fashioned whack? I thought that method only worked with old TVs.

If all else fails, it might be worth a try, just give it a good tap near where the IMU is located.

The fact that one IMU is working means it's not a ribbon cable issue, so dismantling the AC may not fix it.

When you think of the IMU calibration process, the IMU must be in part mechanical (the gyroscope) as you tilt the AC on different axis for it to re-register the neutral point readings.
So the gyro could be jammed from the jarring bike ride, given that you have an issue along the x-axis

 

[Deleted member 94047]

The fact that one IMU is working means it's not a ribbon cable issue, so dismantling the AC may not fix it.

That is actually a very good point and one I haven't considered! Thank you

If all else fails, it might be worth a try, just give it a good tap near where the IMU is located.

The problem is, it is difficult to judge how hard a good tap ought to be.

 

[lannes]

That is actually a very good point and one I haven't considered! Thank you

The problem is, it is difficult to judge how hard a good tap ought to be.

If it is a sticky part and the recent landing didn't resolve anything , then maybe you can just hold it and shake/roll it on all axes and even when it's upside down

 

[lee82gx]

Hi, I was following the thread with great interest. I use MEMS sensors in my work and I suppose the IMU is just a type of MEMS accelerometer. Now personally I don’t have experience with an accelerometer but I do have experience with MEMS charged plates that exhibit stiction issues from time to time. When you mention that your drone was subject to shocks, it comes together to me that your sensor could be suffering from stiction too.

Reference

if you read some of the published materials about accelerometer sticition in certain axis as above link, it also mentions that the same shocks can free the members from stiction. Now how much shock? That is a great question. My guess is if you have already opened up your main board and expose the IMU module, a gentle tap with your index finger should be enough. If all else fails now it seems a replacement of the imu module sourced from the internet is a good idea.
Do let us know what you decided to do.