Critical PREFLIGHT FAIL: EKF HIGH IMU ACCELEROMETER BIAS

fireflysolutions · Mar 21, 2019

Hello,

I am getting high IMU accelerometer bias errors before I launch my H520. I've tried recalibrating the compass and the accelerometer, but with no luck. I'm still able to arm the drone and take off, and it seems much more unstable than normal in angle flight mode with good GPS signal. Has anybody else been having these issues? Any advice?

I'm thinking of just ordering a new IMU unit, if it's only 20 bucks.

Thanks

Steve Carr · Mar 21, 2019

fireflysolutions said:
I'm thinking of just ordering a new IMU unit, if it's only 20 bucks.

Your diagnosis sounds logical. Where did you find an IMU for $20. I thought that was part of the Flight Controller. But I'm curious.

fireflysolutions · Mar 21, 2019

Yuneec Typhoon H Plus/H520/H520E/H850 Flight Controller IMU Module

WTFDproject · Mar 21, 2019

"accelerometer bias out of range" was a common problem on earlier Yuneec products. It happened because of high resistance created by cracked solder. A plug in joint might build up some trace corrosion, causing the same issue. You might be able to clear the issue by unplugging the IMU and try to clean up the pins.

Steve Carr · Mar 21, 2019

fireflysolutions said:
Yuneec Typhoon H Plus/H520/H520E/H850 Flight Controller IMU Module

Kudos to Yuneec. I had no idea the IMU was a separate module on the 520. That is a huge benefit to owners.

arruntus · Mar 22, 2019

I'm not so sure it's a hardware problem, so what I'm reading may be perfectly software. There have been many problems with the firmware PX4 Drone Autopilot, which is based on the one we have in the H520, about this error.

Before buying another IMU unit I would ask in the technical support. Do you have the H520 updated? Have you deleted the values so I can get new ones?

fireflysolutions · Mar 25, 2019

arruntus said:
I'm not so sure it's a hardware problem, so what I'm reading may be perfectly software. There have been many problems with the firmware PX4 Drone Autopilot, which is based on the one we have in the H520, about this error.

Before buying another IMU unit I would ask in the technical support. Do you have the H520 updated? Have you deleted the values so I can get new ones?

I saw the same thing on the PX4 forums. I recently updated the drone and that is around the time I started seeing these issues, but i can't be sure. What do you mean by deleted the values?

arruntus · Mar 25, 2019

fireflysolutions said:
I saw the same thing on the PX4 forums. I recently updated the drone and that is around the time I started seeing these issues, but i can't be sure. What do you mean by deleted the values?

When installing a new version, especially DataPilot, it is convenient to delete all the values contained in the application and configure it from 0. This is because it is possible that the values of the previous version, if you do not delete them, may interfere with the operation of the new version.

How to do it? Very easy, as in any Android application, you go to Settings / App / look for DataPilot and delete all the values, cache and everything. Then you start DataPilot again and configure everything from 0.

RPR · Mar 25, 2019

Steve Carr said:
Kudos to Yuneec. I had no idea the IMU was a separate module on the 520. That is a huge benefit to owners.

IMU has always been a separate unit in all of the drones, even on the H480 and H Plus.

RPR · Mar 25, 2019

arruntus said:
I'm not so sure it's a hardware problem, so what I'm reading may be perfectly software. There have been many problems with the firmware PX4 Drone Autopilot, which is based on the one we have in the H520, about this error.

Before buying another IMU unit I would ask in the technical support. Do you have the H520 updated? Have you deleted the values so I can get new ones?

Once you have the unit or the IMU. You have I rebuild the ST16s and the drone’s firmware, do all the calibration. GYRO, then compass. IMU, followed by RC calibration. This is be the parameters to the physical location of your RC and drone.

Steve Carr · Mar 26, 2019

RPR said:
IMU has always been a separate unit in all of the drones, even on the H480 and H Plus.

No kidding? Can you show me where it is located on the H480?

RPR · Mar 26, 2019

Steve Carr said:
No kidding? Can you show me where it is located on the H480?

stm32f405 is an IMU unit that Yuneec placed on top of the rx and esc control board and I am guessing that MPU for gyro is also in there somewhere, these two are always married to each other.

RPR · Mar 26, 2019

Steve Carr · Mar 26, 2019

If you look back at post # 2, I indicated it was part of the Flight Controller. Your photo is the FC.
I did not realize they separated it on the 520 and probably the H as well. But on the 480 it is on the FC.

RPR · Mar 26, 2019

Steve Carr said:
If you look back at post # 2, I indicated it was part of the Flight Controller. Your photo is the FC.
I did not realize they separated it on the 520 and probably the H as well. But on the 480 it is on the FC.

They did a great job on the H520 and the H Plus. The unit can also be removed and tested via Qdroundcontrol which is awesome. Will test my IMU peaks probably test mine in the fall, once I’m out of warranty.

arruntus · Mar 26, 2019

RPR said:
IMU has always been a separate unit in all of the drones, even on the H480 and H Plus.

No companion, depends only on the manufacturer, there are many drones that have a separate module and others, the vast majority that have it integrated into the flight controller and therefore is only one device.

Yuneec has opted this time to have it apart, despite making a customized version of PX4, but because they wanted, there is nothing that would have prevented doing it integrated (in principle).

And yes, in case of failure, for us it is much better that this all modulated and we only have to change the parts.

RPR said:
Once you have the unit or the IMU. You have I rebuild the ST16s and the drone’s firmware, do all the calibration. GYRO, then compass. IMU, followed by RC calibration. This is be the parameters to the physical location of your RC and drone.

I'm sorry, I don't understand what you mean

RPR · Mar 26, 2019

arruntus said:
I'm sorry, I don't understand what you mean

After resetting to factory:

Calibrate.

1) Gyro
2) Compass
3) RC
4) Turn off AC, then RC

*Leave AC in cold room (I leave mine in the garage overnight)

5) Cold IMU calibration

Once calibrated, the final calibration will be the compass at the field.

arruntus · Mar 26, 2019

RPR said:
After resetting to factory:

Calibrate.

1) Gyro
2) Compass
3) RC
4) Turn off AC, then RC

*Leave AC in cold room (I leave mine in the garage overnight)

5) Cold IMU calibration

Once calibrated, the final calibration will be the compass at the field.

Understood, please tell us if the problem has been solved

fireflysolutions · Mar 27, 2019

Thanks for the assist, followed all steps above and no more high accelerometer bias error. After one test flight the drone is performing much better, however, the drone is still relatively unstable in low wind conditions. Additionally, when I yaw left or right, the drone does not just spin about it's vertical axis it actually makes a U-turn.

Any thoughts or remedies to help the wandering drone? Is it possible that the camera/gimbal has anything to do with it? Having some issues fully calibrating the gimbal...