Mavic Mini Fly Away?

[slup]

... and why not re-calibrate it?

Think you've got a good understanding about nearly all the crucial bits regarding how to avoid a yaw error due to magnetic disturbance & a deflected compass ...

1. You understand that the error occurs during power on ... if the compass is magnetically deflected at that moment, the IMU will be wrongly initialized. And by that the AC will not know in which direction it's actually pointing there after ... meaning that the flight controller will command the wrong motors when trying to hold position when the AC starts to be affected by outside forces, like wind. This will in turn generate a positional error loop that rapidly increase the positional error... this will make your AC fly away in a very hard to control manner.

2. You also grip that you can check that the IMU have been correctly initialized before take off ... After powering on your AC, connected to your RC/app & placed it in the take-off spot ... but before lift-off, you check that the "drone icon" on the map in your app is pointing equal in relation to other objects in the map as the AC does in reality ... if it doesn't, you abort the launch attempt, power down, move away, power up again and repeat.


The thing you doesn't seem to fully understand is what a calibration actually does ... the intent with a compass calibration is to only measure the AC own internal magnetic field in order to be able to deduct it so the earth magnetic field can be measured accurately.

So by that ... a compass calibration is only needed when something have been changed on the AC itself ... either extra equipment attached or taken off ... that's why the DJI app message is wrong when the AC have been placed in a magnetic interfered environment ... as nothing have been changed on the AC. Carry the AC outside that interference & the message will be gone. What you instead need to do is follow the instructions under point 2. above.

 

[Meta4]

i mean, if u have this situation its logical that u should change position because u have some sort of interference on compass, and why not re-calibrate it?
If i i got this all right, when u power on drone and its doing sistems check up, if u are in some sorth of magnetic interference while its powering on then your compass wont be accurate = unsafe to take off

When you understand how the compass works and what calibrating it actually does, you understand that there is nothing wrong with it that needs to be "fixed".
It's already perfectly calibrated and that doesn't change.
Recalibrating won't achieve anything at all.

 

[Sallee]

Think you've got a good understanding about nearly all the crucial bits regarding how to avoid a yaw error due to magnetic disturbance & a deflected compass ...

1. You understand that the error occurs during power on ... if the compass is magnetically deflected at that moment, the IMU will be wrongly initialized. And by that the AC will not know in which direction it's actually pointing there after ... meaning that the flight controller will command the wrong motors when trying to hold position when the AC starts to be affected by outside forces, like wind. This will in turn generate a positional error loop that rapidly increase the positional error... this will make your AC fly away in a very hard to control manner.

2. You also grip that you can check that the IMU have been correctly initialized before take off ... After powering on your AC, connected to your RC/app & placed it in the take-off spot ... but before lift-off, you check that the "drone icon" on the map in your app is pointing equal in relation to other objects in the map as the AC does in reality ... if it doesn't, you abort the launch attempt, power down, move away, power up again and repeat.


The thing you doesn't seem to fully understand is what a calibration actually does ... the intent with a compass calibration is to only measure the AC own internal magnetic field in order to be able to deduct it so the earth magnetic field can be measured accurately.

So by that ... a compass calibration is only needed when something have been changed on the AC itself ... either extra equipment attached or taken off ... that's why the DJI app message is wrong when the AC have been placed in a magnetic interfered environment ... as nothing have been changed on the AC. Carry the AC outside that interference & the message will be gone. What you instead need to do is follow the instructions under point 2. above.

thanks man, u were thorough .. I think that most important thing is to recognize problematic situations in this case, when directions of drone do not match direction on the map, so people should know that they should not take off in that situation.. am i right? to avoid potential problems in flight like "bathtub" curved flight etc...
@Meta4 my MM usually want to re-calibrate compass when i change location more then 100km away (from location where i fly), should i do it or not? I mean, there is no harm done to do it even when is ''false alarm''

 

[slup]

...when directions of drone do not match direction on the map, so people should know that they should not take off in that situation.. am i right?

As the map view in the app can be set to either have North up always ... or being pointing to actual North (map view rotates when you rotate) ...

It's important to state it like " ...pointing equal in relation to other objects in the map as the AC does in reality". So if the front of the drone is facing a road or a house in reality the drone icon should do that on the map also ... no matter how the map itself is rotated.

This is an easy check you can do before take-off & it will sooner or later save you from a lot of sorrow.

...my MM usually want to recalibrate compass when i change location more then 100km... should i do it or not? I mean, there is no harm done to do it even when is ''false alarm''

Yep ... DJI have some firmware's which force you to do a calibration depending on either time or distance from the last calibration. And it's totally unnecessary ... time or distance will not change the drones own internal magnetic interference.

But as you can't go around it you need to do it ... it will in general not mess anything up, just make sure you do it without influence of magnetic interference.

And I said in general above due to a reason ... a calibration can pass & be considered OK by the app, but the quality of it isn't equal from one calibration to another. The remaining calibration error ... or end result, is stated in the .DAT log & it can differ quite a lot. A bad ...but according to the app OK calibration, can induce crabbing in flight ... the drone don't fly nose straight forward instead it flies slightly sideways which can be somewhat disturbing when you try to aim on a distant object but when you fly forward you don't end up flying quite in that direction.

 

[Meta4]

my MM usually want to re-calibrate compass when i change location more then 100km away (from location where i fly), should i do it or not? I mean, there is no harm done to do it even when is ''false alarm''

It only does that because DJI (for no reason that anyone can work out) makes it do that.
There is no physical reason that the compass needs to be recalibrated at 100 km or even 1000 km distance.

 

[Sallee]

thanks people, i think i got it.. i even didnt consider to take off without re-calibrating compass when i am asked to do, so i always do it.. but every time before take off i always check real orientation of drone on the map and in the filed
new info for me is that when i see that drone is ''drifting'' from course - not going straight in a line, that it compass problem and i should re-calibrate it

 

[Meta4]

new info for me is that when i see that drone is ''drifting'' from course - not going straight in a line, that it compass problem and i should re-calibrate it

If you really had a compass problem, the drone wouldn't just drift off course, it would have trouble sitting still and would slowly spiral.
But that's not something you should expect to see.
Once teh compass is calibrated, it doesn't lose calibration unless you modify the drone by adding or removing things that change the magnetic fields that are part of the drone.