Crash during auto take-off

[lengthlord]

It would seem the compass is not functioning. Is it fair to assume that this caused the crash and DJI should repair or replace the drone under the warranty at no cost to me?

 

[BudWalker]

Thanks, I first did a factory reset using the DJI Assistant 2 app and a successful IMU calibration. Then I took the AC to a field and performed your test Spy808. The result was that the arrow icon in the app did not rotate when rotating the AC. Strangely when adjusting the pitch of the AC the direction of the icon did change!

A red Compass Error message appeared in the app several times, disappearing to be replaced with a green Ready to Go message.



I’m not sure I follow you. Do you mean to say that simply powering up the drone, or using the app simulator, which requires the drone to be powered on, can damage the compass?

Actually this test shows that there is a problem with the IMU, probably one or more of the gyros.It's only at batteryOn when the compass is used to initialize the Yaw value. After that it's mostly the IMU that's used to determine Yaw with the compass providing small corrections.This would explain why initial Yaw wasn't compromised. It also explains why the "compass error" occurred after launch. It's not literally a compass error. Rather, the label "compass error" means that there is a discrepancy between the Yaw value (derived from the IMU data) and the yaw value derived from the compass. This probably also explains why you saw a Yaw change when adjusting pitch.

Should've seen this. At 4.4. secs full negative rudder for about 2 secs but there was no change in Yaw value.


Maybe you can get the tablet .DAT for this test.

 

[sar104]

It would seem the compass is not functioning. Is it fair to assume that this caused the crash and DJI should repair or replace the drone under the warranty at no cost to me?

That does seem to be the case. If you look at those two flights, the yaw was initialized at different values but basically did not change during the flights except with pitch/roll excursions, even though full rudder was applied during both flights:





I think that they will replace it under warranty.

 

[sar104]

Actually this test shows that there is a problem with the IMU, probably one or more of the gyros.It's only at batteryOn when the compass is used to initialize the Yaw value. After that it's mostly the IMU that's used to determine Yaw with the compass providing small corrections.This would explain why initial Yaw wasn't compromised. It also explains why the "compass error" occurred after launch. It's not literally a compass error. Rather, the label "compass error" means that there is a discrepancy between the Yaw value (derived from the IMU data) and the yaw value derived from the compass. This probably also explains why you saw a Yaw change when adjusting pitch.

Should've seen this. At 4.4. secs full negative rudder for about 2 secs but there was no change in Yaw value.
View attachment 36546

Maybe you can get the tablet .DAT for this test.

I think it's almost certainly the case that the z-axis rate gyro is dead - there is no way that the yaw value would remain constant if the z-axis rate gyro were working. Once there was non-zero pitch and roll then then the x- and y-axis rate gyros will have contributed to the yaw calculation - hence the yaw variations at that point.

 

[Spy808]

Thanks, I first did a factory reset using the DJI Assistant 2 app and a successful IMU calibration. Then I took the AC to a field and performed your test Spy808. The result was that the arrow icon in the app did not rotate when rotating the AC. Strangely when adjusting the pitch of the AC the direction of the icon did change!

A red Compass Error message appeared in the app several times, disappearing to be replaced with a green Ready to Go message.



I’m not sure I follow you. Do you mean to say that simply powering up the drone, or using the app simulator, which requires the drone to be powered on, can damage the compass?

The first & second part of ür test ü followed is correct... Icon on dji app supposed to move when u physically twist the drone in any position immediately... So ur gps\compass is bad cause ur imu calibrated good u say... I wouldn't try to fly it anymore sad to say...

 

[BudWalker]

The first & second part of ür test ü followed is correct... Icon on dji app supposed to move when u physically twist the drone in any position immediately... So ur gps\compass is bad cause ur imu calibrated good u say... I wouldn't try to fly it anymore sad to say...

That's not right. This test shows the IMU is not working correctly. See my post # 62 and @sar104 's post # 64.

 

[BudWalker]

2018-04-19_18-22-26_FLY033.DAT is a tablet .DAT provided by @lengthlord where he was trying to do a compass calibration. There were multiple rotations about the Z axis.

It can be seen that magYaw (the compass Yaw value) rotates through 1440° (4 rotations). But totalGyroZ (the integral of gyroZ) only increases by 1.65°. Clearly, the gyroZ is malfunctioning. Notice also the MAG_YAW_ERRORs shown with the pink background. If only we had though to look at this possibility....

 

[sar104]

2018-04-19_18-22-26_FLY033.DAT is a tablet .DAT provided by @lengthlord where he was trying to do a compass calibration. There were multiple rotations about the Z axis.
View attachment 36564
It can be seen that magYaw (the compass Yaw value) rotates through 1440° (4 rotations). But totalGyroZ (the integral of gyroZ) only increases by 1.65°. Clearly, the gyroZ is malfunctioning. Notice also the MAG_YAW_ERRORs shown with the pink background. If only we had though to look at this possibility....

That's definitive.

 

[lengthlord]

@BudWalker, @sar104, @Spy808 you guys are awesome thank you so much and thank you to everyone else who helped too.

Apologies for my late response, I’ve had a very busy day. I will talk to DJI support and request a repair or replacement. Is everyone happy for me to send DJI your research, should I need to support my claim? Is there anything I should be wary of saying when talking with DJI? This is my first DJI drone so I’ve never dealt with them before and don’t know what to expect.

 

[BudWalker]

@BudWalker, @sar104, @Spy808 you guys are awesome thank you so much and thank you to everyone else who helped too.

Apologies for my late response, I’ve had a very busy day. I will talk to DJI support and request a repair or replacement. Is everyone happy for me to send DJI your research, should I need to support my claim? Is there anything I should be wary of saying when talking with DJI? This is my first DJI drone so I’ve never dealt with them before and don’t know what to expect.

Go for it.

 

[rfc]

I've discovered how to keep .DATs from being recorded on the flash memory in the first place. Basically, the SD card is kept close to empty by periodically deleting the .DATs from the SD card. So far, all of my new flights get recorded on the SD card where I can get them. I've been doing this for a month or so and it has worked every time so far. My Mavic has been rooted but I don't think that matters.

Here's my method for deleting .DATs from the SD card.
1) Connect USB port to the PC and then start a FTP client (I use FileZilla).
2) connect to 192.168.42.2 with UserName = nouser, Password = nopass, port = 21
3) On the remote site (i.e., the Mavic) navigate to the /blackbox/flyctrl directory and delete the .DATs you don't want.
.

Is the definitive way to determine that this works, to just see if the dat files are there after a flight?
How often should this be done? Is there a way to see the SD card percentage full capacity?

 

[BudWalker]

Is the definitive way to determine that this works, to just see if the dat files are there after a flight?
How often should this be done? Is there a way to see the SD card percentage full capacity?

I started a thread on this. Could you re-post there please.
Keeping .DATs on the Mavic Pro accessible

 

[rfc]

Will do Sir. Missed that thread completely. Thanks for your efforts.

 

[bentbrent]

I have a new Mavic Pro drone. After calibrating the compass and IMU I flew it successfully for the first time yesterday.

Today, after updating the firmware and Fly Safe databases I tried to fly the drone again in a location about 300 metres from the first location. The grass was a little long so I placed the drone on a large flat picnic table. I did all the pre flight checks and when the app showed "Ready to go" I tapped the takeoff icon and then slid the takeoff slider. The drone began to rise and when still low in the air it moved to the right and began to spiral back towards me. I tried to counter these movements with the controller but this seemed to have no effect and the drone quickly flew towards a bush and then hit the ground. The drone had a few grass stains but there appeared to be no damage.

I thought perhaps taking off from the picnic table had confused the sensors so I tried to fly the drone again from a small patch of ground without grass, using the same auto takeoff feature. The same thing happed again with the drone spiralling and flipping on to the grass. Again the drone seemed to be ok. I realised something was wrong and decided not to attempt another flight until I got to the bottom of the issue.

I then read some forum posts about similar incidents with replies suggesting IMU and compass calibration. I successfully calibrated the IMU but the compass calibration wouldn't complete with the app continuing to show the screen asking to rotate the drone horizontally.

The only differences to the drone from yesterday's successful flight were:

1. A different battery was used, which did not have a firmware update. (The battery used yesterday was in the drone when I updated the firmware.)
2. The propeller guards were fitted
3. DJI Goggles had been paired with the drone but were not used during the flights

I've uploaded the DAT file for the 2 flights here: Dropbox - DJI_ASSISTANT_EXPORT_FILE_2018-04-19_22-08-22.DAT

Any help in understanding what went wrong and what I should do next would be much appreciated.

Many thanks

I have a new Mavic Pro drone. After calibrating the compass and IMU I flew it successfully for the first time yesterday.

Today, after updating the firmware and Fly Safe databases I tried to fly the drone again in a location about 300 metres from the first location. The grass was a little long so I placed the drone on a large flat picnic table. I did all the pre flight checks and when the app showed "Ready to go" I tapped the takeoff icon and then slid the takeoff slider. The drone began to rise and when still low in the air it moved to the right and began to spiral back towards me. I tried to counter these movements with the controller but this seemed to have no effect and the drone quickly flew towards a bush and then hit the ground. The drone had a few grass stains but there appeared to be no damage.

I thought perhaps taking off from the picnic table had confused the sensors so I tried to fly the drone again from a small patch of ground without grass, using the same auto takeoff feature. The same thing happed again with the drone spiralling and flipping on to the grass. Again the drone seemed to be ok. I realised something was wrong and decided not to attempt another flight until I got to the bottom of the issue.

I then read some forum posts about similar incidents with replies suggesting IMU and compass calibration. I successfully calibrated the IMU but the compass calibration wouldn't complete with the app continuing to show the screen asking to rotate the drone horizontally.

The only differences to the drone from yesterday's successful flight were:

1. A different battery was used, which did not have a firmware update. (The battery used yesterday was in the drone when I updated the firmware.)
2. The propeller guards were fitted
3. DJI Goggles had been paired with the drone but were not used during the flights

I've uploaded the DAT file for the 2 flights here: Dropbox - DJI_ASSISTANT_EXPORT_FILE_2018-04-19_22-08-22.DAT

Any help in understanding what went wrong and what I should do next would be much appreciated.

Many thanks

Lengthlord

I'm a newbie myself, but don't forget that it took a child to tell the emperor that he had no clothes.I hope I can help. In the app, if you click on the drone symbol and scroll to the bottom, you will see advanced settings. At the bottom of the advanced settings, there is a switch to check for 'prop guards installed'. If you didn't check that, it may be causing your problem.

Best regards,

Bentbrent

 

[lengthlord]

Lengthlord

I'm a newbie myself, but don't forget that it took a child to tell the emperor that he had no clothes.I hope I can help. In the app, if you click on the drone symbol and scroll to the bottom, you will see advanced settings. At the bottom of the advanced settings, there is a switch to check for 'prop guards installed'. If you didn't check that, it may be causing your problem.

Best regards,

Bentbrent

Thanks, but I believe this setting is for the propeller cage, not the propeller guards. https://forum.dji.com/thread-89165-1-1.html

 

[tunegutt]

Hi Lengthlord,

I have the exact same problem with a brand-new out of the box mavic pro. I only attempted two flights. Both times the Mavic took off and at a hight of 1m it starting spiraling out of control resulting in a crash. I then had the compass error and just like with your drone I’m unable to calibrate the compass. Only if I tilt the drone on its side it would give me green lights during compass calibration. Did you get on to DJI? What did they suggest? Did you send the drone in for repair? Did the replacement drone behave as expected?

Cheers!

 

[lengthlord]

Hi Lengthlord,

Did you get on to DJI? What did they suggest? Did you send the drone in for repair? Did the replacement drone behave as expected?

Cheers!

Hi tunegutt, I was away from home so could not send the drone back until this week. Also I first wanted to try if downgrading the firmware fixed the issue, which it did not. I've created a DJI repair request but as yet I've not received a response form them.

Have you tried downgrading your firmware? Have you contacted DJI?