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attitude drift in manual mode
1725 16 2021-5-15
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luciens
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Has anyone else noticed a very slow drifting of pitch or roll (or both) in manual mode? Meaning, put the FPV drone in a stable hover, or stable straight ahead forward flight in manual mode, and the let the pitch/roll stick center and keep it there.

I have two FPV drones, one will slowly drift nose-up and the other will slowly drift nose-up and to the right. Rather like a helicopter slightly out of trim. But of course, there's no way to trim any of the controls, so I can't null this out and I have to constantly correct for it.

No problems in normal or sport mode. It only happens in manual mode.

Yes, I have:
- calibrated the remote.
- calibrated the IMU
- calimbrated the compass
- calibrated the camera gimbal.


2021-5-15
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fans6e2a67c1
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I’ve got even worse scenario.
Drone lost signal for a second, when I was doing drop close to huge waterfall. Then I’ve got back signal but instead of hovering it was flying backwards. I’ve tried to fly forward. Didn’t work.
Drone crashed by itself in waterfall. DJI support doesn’t explain why drone was drifting backwards and did not react on any joystick motion.
Any ideas what to do in future? because I’m thinking about changing platform from DJI. If it can kill itself and DJI care doesn’t support this type of scenario.
2021-6-6
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djiuser_ULOj7ZoSHtHF
lvl.2
Flight distance : 6135892 ft
Thailand
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Flown it straight for 3km and back, didn't notice any drift
2021-6-7
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Cobani
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But... in manual mode YOU ARE the pilot, there is not any assist in these mode. You don't have GPS hovering, and all the positioning assistances are deactivated. Full manual meaning that the drift it's produced by the wind, and you are the responsible to correct them.
You don't have any drift in NORMAL and SPORT because these modes are GPS assisted and the drone fix any mispositioning because of the wind. In manual doesn't exist any assist, it's only your drone and your inputs. Nothing else.

It's the normal behavior.
2021-6-7
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luciens
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Cobani Posted at 6-7 08:04
But... in manual mode YOU ARE the pilot, there is not any assist in these mode. You don't have GPS hovering, and all the positioning assistances are deactivated. Full manual meaning that the drift it's produced by the wind, and you are the responsible to correct them.
You don't have any drift in NORMAL and SPORT because these modes are GPS assisted and the drone fix any mispositioning because of the wind. In manual doesn't exist any assist, it's only your drone and your inputs. Nothing else.

No, the gyros should not drift even in manual mode and it has nothing to do with the wind. Without control inputs, they should hold the current attitude of the aircraft for much longer than they currently do. I'm not referring to the active position holding in the GPS assisted modes, or drift over the ground with the airmass, etc.

The behavior is like a slightly out-of-trim helicopter. You can reproduce it even in a hover - put the aircraft in a particular position and then let go of the sticks. Observe the attitude in the goggles - you'll notice the aircraft ever so slowly pitches upward. On one of my drones it also drifts in attitude to the right and to left in yaw. The other drifts in a similar way but not as bad.

Often this is caused by too low of an I-term, but it can also be a problem with the gyros themselves. Though since I'm seeing this on more than one, I figure it's probably just a tuning issue, likely too low of an I-term.....
2021-6-7
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djiuser_ULOj7ZoSHtHF
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luciens Posted at 6-7 08:23
No, the gyros should not drift even in manual mode and it has nothing to do with the wind. Without control inputs, they should hold the current attitude of the aircraft for much longer than they currently do. I'm not referring to the active position holding in the GPS assisted modes, or drift over the ground with the airmass, etc.

The behavior is like a slightly out-of-trim helicopter. You can reproduce it even in a hover - put the aircraft in a particular position and then let go of the sticks. Observe the attitude in the goggles - you'll notice the aircraft ever so slowly pitches upward. On one of my drones it also drifts in attitude to the right and to left in yaw. The other drifts in a similar way but not as bad.

Maybe you can upload a video to show us better how big is this drift, as said can't notice any on mine, I calibrated the sticks once and nothing else
2021-6-7
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luciens
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djiuser_ULOj7ZoSHtHF Posted at 6-7 08:46
Maybe you can upload a video to show us better how big is this drift, as said can't notice any on mine, I calibrated the sticks once and nothing else

Yeah next time I get an opportunity to fly, I'll try to upload a video of it....
2021-6-7
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djiuser_ULOj7ZoSHtHF
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luciens Posted at 6-7 08:53
Yeah next time I get an opportunity to fly, I'll try to upload a video of it....

The gyro should calibrate itself at each power up, try to leave it on the ground and not touch it until fully initialized
2021-6-7
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Vertigocal
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Cobani Posted at 6-7 08:04
But... in manual mode YOU ARE the pilot, there is not any assist in these mode. You don't have GPS hovering, and all the positioning assistances are deactivated. Full manual meaning that the drift it's produced by the wind, and you are the responsible to correct them.
You don't have any drift in NORMAL and SPORT because these modes are GPS assisted and the drone fix any mispositioning because of the wind. In manual doesn't exist any assist, it's only your drone and your inputs. Nothing else.


What I ask myself now is what happens in manual mode when the drone loses connection.
Does it stop and hover or will it fly further without control?
2021-6-8
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luciens
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djiuser_ULOj7ZoSHtHF Posted at 6-7 22:26
The gyro should calibrate itself at each power up, try to leave it on the ground and not touch it until fully initialized

Agree, I do that on every flight. But both of my drones still drift, though one is a little better than the other one.
2021-6-8
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tomekyo
Second Officer
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Netherlands
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I either misunderstand your words or you don't fully understand what manual mode should be like. Drift would mean there is some input which pushes the drone to one particular side and you have to fight it with your sticks. This is not how manual mode works. The drone should (more or less) keep the last position you leave it in and is it fights it the problem should be in the remote, creating input. The sticks not cantering properly for instance. Only problem with this theory is that you'd experience the same in all other modes. Anybody, please correct me if you think I am wrong ...
2021-6-8
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luciens
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tomekyo Posted at 6-8 12:12
I either misunderstand your words or you don't fully understand what manual mode should be like. Drift would mean there is some input which pushes the drone to one particular side and you have to fight it with your sticks. This is not how manual mode works. The drone should (more or less) keep the last position you leave it in and is it fights it the problem should be in the remote, creating input. The sticks not cantering properly for instance. Only problem with this theory is that you'd experience the same in all other modes. Anybody, please correct me if you think I am wrong ...

Yes, it's the maintenance of the aircraft attitude without stick inputs (in manual mode) that I'm referring to. When I say "drift", I mean the attitude of the aircraft is changing slowly (without pilot input) which it should not do, if the tune is good and the gyros were functioning correctly. It happens regardless of any upsetting forces acting on it (like the relative wind). It can be reproduced in a hover or in any flight regime.

And it only does it in manual mode. In the assisted modes (Normal and Sport), this doesn't happen (because those modes actively maintain the aircraft's position in space, so attitude is automatically adjusted actively by autopilot at all times).

It's not the controller - I actually have two controllers and the drift is the same with both of them. There's also no way to trim the drifting tendencies out with the controller, but that shouldn't be necessary. The aircraft should maintain its attitude in manual mode without having to do trim adjustments (if there were any).
2021-6-8
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fans1c3d0833
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I don't have this issue with my own, but I have a few things I can think of to try. [1] check if the stick has any mechanical play at center. [2] try low center sensitivity (50) and high expo (0.75). [3] check the arms and motors if there's anything loose. [4] try a new set of props.
[1] and [2] are for inputs and data resolutions. [3] and [4] are for vibration which can throw off IMU.
2021-6-8
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BudWalker
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Perhaps a better question is how can it not drift. In M mode the Flight Controller is not correcting attitude. I noticed that my FPV has a roll drift and took a closer look at the data. Here is an interval where the FPV was in manual mode with yaw, roll and pitch control inputs at 0.0, i.e.neutral. Throttle was a constant -0.3`

2021-06-14_7-39-31.jpg
IMU:roll is computed by the FC and shows a 1° CCW roll. totalGyrX is the time integrated gyroX data and shows a 2° CCW roll. It's not that the gyroX isn't calibrated or somehow incorrect. Rather, the FC isn't attempting to correct the roll drift.
2021-6-14
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luciens
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BudWalker Posted at 6-14 06:51
Perhaps a better question is how can it not drift. In M mode the Flight Controller is not correcting attitude. I noticed that my FPV has a roll drift and took a closer look at the data. Here is an interval where the FPV was in manual mode with yaw, roll and pitch control inputs at 0.0, i.e.neutral. Throttle was a constant -0.3`

[view_image]

I agree, it's not possible for it to be rock solid forever. But the drift in my FPV drones is a bit more than I think is normal. Especially compared to my Betaflight/ F4/F7 quads, which drift far far less in attitude.

Here's a video I took of my worse-drifting drone that shows how much it drifts and how quickly. I have EIS on to get rid of any wobbling in the video. I get the aircraft in a kinda-sorta stable hover attitude and then let go of both sticks. You can see an immediate pitch upwards and to the right. At the end of it I grab the sticks to keep it from flying into the next county

2021-6-14
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BudWalker
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luciens Posted at 6-14 07:08
I agree, it's not possible for it to be rock solid forever. But the drift in my FPV drones is a bit more than I think is normal. Especially compared to my Betaflight/ F4/F7 quads, which drift far far less in attitude.

Here's a video I took of my worse-drifting drone that shows how much it drifts and how quickly. I have EIS on to get rid of any wobbling in the video. I get the aircraft in a kinda-sorta stable hover attitude and then let go of both sticks. You can see an immediate pitch upwards and to the right. At the end of it I grab the sticks to keep it from flying into the next county

That does seem to be a bit much. If you're interested you could retrieve the .DAT and we could take a look. This post explains how to retrive the .DAT
https://fpvdronepilots.com/threads/dat-available.4225/#post-35016
2021-6-14
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luciens
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BudWalker Posted at 6-14 08:51
That does seem to be a bit much. If you're interested you could retrieve the .DAT and we could take a look. This post explains how to retrive the .DAT
https://fpvdronepilots.com/threads/dat-available.4225/#post-35016

I don't dare plug either of my drones into DJI Fly, with the corrupt FlySafe DB possibly being forced onto them. I spent too much on them to risk bricking them with broken firmware, so they're not going within 100 miles of the Internet, probably forever. Maybe if DJI fixes the flysafe problem and releases a firmware update, but otherwise they're never going to be plugged into any smart device ever again.

Both drones do this, though the other drifts to the left instead, and it's not quite as bad as this one. So I've just gotten used to it at this point and just fly them as-is.
I was just curious if anyone else was seeing this on theirs. It might be as simple as too low of an I-term in the PIDs....
2021-6-14
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