A lot of learning today! (AC internal vibration and home-point reset)

[Vaideeshwar]

Hello!
I have been proudly and happily flying my MA2 for over 3 weeks now. Having previously flown the MM and the MA, I am used to both control apps, and DJI Fly was nothing to me.

HOWEVER, two very weird things happened today which I have never experienced.

1. As usual, I turned on the RC first, opened the Fly app, then turned the AC on (while on ground at point X) and waited for GPS lock, plenty of satellites, and for the home point to be set (the whole thing took about 30 secs I would say). After all that, I picked up the AC to move it to point Y, a meter away from point X. When I picked it up, I felt a strong vibration (much like a vibrating cellphone) and heard a noise (I would describe it as the noise you would hear when you rub a steel knife against a rusted iron plate). I saw no warnings, whatsoever, except for IMU Attitude Error which is because of me lifting the AC and moving it to point Y.

2. In the same flight, I lost connection with the aircraft, which isn't unusual, but this time around, the Fly app crashed and I had to re-open it. When I did so, it initially said said "AC not connected to RC", but then said "Home-point has been updated, please check it on the map". My heart skipped a beat, but I was relieved when I noticed that it was the same homepoint I initially set at X. When I looked at the flight logs, I actually saw two different ones- one until the app was disconnected and the other from when I restarted the app!!

I can't help but think about the worst; what would happen if the HP was updated at the then-current location of the AC!?

Would love to hear your experiences on both these issues, if you've ever encountered them.

 

[boblui]

The only moving thing inside the drone should be the cooling fan. May be a piece of debris or dropped-out screw hit the fan and produced the noise ?

 

[Vaideeshwar]

The only moving thing inside the drone should be the cooling fan. May be a piece of debris or dropped-out screw hit the fan and produced the noise ?

That or, have you ever pitched/rolled a laptop with a cooling fan? Heard how it sounds? (Because of gyroscopic effect) I was thinking it could be that, but it didn't happen when I tried it again when the fan was running. It is in pristine condition, so I am confident there isn't dust or small gravel. I think a loose screw is also not possible since I tried shaking the aircraft while off and without props to hear nothing resembling the sound of rattle. Pretty baffling imo.

 

[Meta4]

2. In the same flight, I lost connection with the aircraft, which isn't unusual, but this time around, the Fly app crashed and I had to re-open it. When I did so, it initially said said "AC not connected to RC", but then said "Home-point has been updated, please check it on the map". My heart skipped a beat, but I was relieved when I noticed that it was the same homepoint I initially set at X. When I looked at the flight logs, I actually saw two different ones- one until the app was disconnected and the other from when I restarted the app!!

I can't help but think about the worst; what would happen if the HP was updated at the then-current location of the AC!?

Normally the drone records its homepoint as soon as it gets good GPS position data.
Normally the homepoint would only change if you change it.
Losing connection should not make any difference.
It would be interesting to see your flight data to work out what's happened.
Can you post your .txt files?

 

[fGene]

The cooling fan would be my prime suspect, too. It might not be debris but a lose wire or something of that sort (manufacturing defect). Can you hear the fan rotating when you power on the aircraft, does it sound normal? If not, I wouldn't fly it at all, the mainboard overheats pretty easily and might cause any kind of glitch.

 

[old man mavic]

may i ask why you moved the drone from the recorded home point to a new position before you took of its not something thats usually done

 

[Vaideeshwar]

may i ask why you moved the drone from the recorded home point to a new position before you took of its not something thats usually done

Sure! I fly from my balcony. Point X in the balcony is where I turned the drone on and let it settle. I realized there was a fair bit of dust there, so I moved it a tad bit to ahead (point Y) to prevent dust from getting into the rotating parts. If there comes a situation where RTH is auto initiated, the AC approaching either points don't matter at all (although it will come to X) becsuse it is literally a meter apart.

 

[Vaideeshwar]

Normally the drone records its homepoint as soon as it gets good GPS position data.
Normally the homepoint would only change if you change it.
Losing connection should not make any difference.
It would be interesting to see your flight data to work out what's happened.
Can you post your .txt files?

Sure, would the mobile .txt files work?

 

[Meta4]

Sure, would the mobile .txt files work?

Yes ... they are the ones needed.

 

[Vaideeshwar]

The cooling fan would be my prime suspect, too. It might not be debris but a lose wire or something of that sort (manufacturing defect). Can you hear the fan rotating when you power on the aircraft, does it sound normal? If not, I wouldn't fly it at all, the mainboard overheats pretty easily and might cause any kind of glitch.

That's what confuses me. I tried turning the AC on and off, and moving it like I originally did with my hand several times before take off to see if the vibration+noise happens again. But NOPE. And the sound of the cooling fan is normal. Nothing weird at all.

 

[Vaideeshwar]

That's what confuses me. I tried turning the AC on and off, and moving it like I originally did with my hand several times before take off to see if the vibration+noise happens again. But NOPE. And the sound of the cooling fan is normal. Nothing weird at all.

Yep! Here they are. Like I mentioned, there are two flight records- one before the app crashed, and the other post app restart. The smaller one (file size) should be the file containing all events before the app crashed.

 

[Meta4]

2. In the same flight, I lost connection with the aircraft, which isn't unusual, but this time around, the Fly app crashed and I had to re-open it. When I did so, it initially said said "AC not connected to RC", but then said "Home-point has been updated, please check it on the map". My heart skipped a beat, but I was relieved when I noticed that it was the same homepoint I initially set at X. When I looked at the flight logs, I actually saw two different ones- one until the app was disconnected and the other from when I restarted the app!!

Maybe there was some confusion there.
Your app did advise you that the homepoint had been updated ... but this was at 0:02.5, just as the drone was taking off.
It's common for the app to update the homepoint very early in the flight when it gets better GPS position data than it initially had.

The homepoints in your flight data were:
Time_____ Lat _____________Long
0:00.5 _ 33.00023877 _ -96.73717409 Initial HP
0:02.5 _ 33.00017558_ -96.73716377 Updated HP
6:56.6 _ 33.00017558_ -96.73716377 Signal lost
7:09.5 _ 33.00017558 _ -96.73716377 App restarted

As you can see the homepoint that was updated at 2.5 secs is the same one that was showing at loss of signal.
And the same as the one shown in the app when it was restarted.
Everything was as it should be.
The stored homepoint in the drone will not change unless you change it.

 

[Vaideeshwar]

Maybe there was some confusion there.
Your app did advise you that the homepoint had been updated ... but this was at 0:02.5, just as the drone was taking off.
It's common for the app to update the homepoint very early in the flight when it gets better GPS position data than it initially had.

The homepoints in your flight data were:
Time_____ Lat _____________Long
0:00.5 _ 33.00023877 _ -96.73717409 Initial HP
0:02.5 _ 33.00017558_ -96.73716377 Updated HP
6:56.6 _ 33.00017558_ -96.73716377 Signal lost
7:09.5 _ 33.00017558 _ -96.73716377 App restarted

As you can see the homepoint that was updated at 2.5 secs is the same one that was showing at loss of signal.
And the same as the one shown in the app when it was restarted.
Everything was as it should be.
The stored homepoint in the drone will not change unless you change it.

Okay, so, the "Intial HP" and the "Updated HP" are not significantly apart, and are pretty much the same spot where I took off from. At signal loss, the HP is the same as the Updated HP. All this is true.

The app crashed after signal loss and the AC initiated RTH. A separate flight log was created (also attached) after I restarted the app:

the "TO ROUTE" (every event pre app crash)


the "FRO ROUTE" (events after app restart)

Like mentioned in this picture, I got the "Home Point has been updated, please check it on the map" notification on my cellphone at about this point after the app restart. I panicked because I thought the app was going to set the then-current location of the drone as the HP, but luckily it did not.

Also, the AC was in RTH during the app crash. So maybe it is a case where, if the AC is in RTH when the app crashes, then after restart, the app adopts the RTH destination point (as stored in the AC), resulting in the "new HP" (post-restart) to be coincident with the "old HP" (pre-crash)

 

[SkyeHigh]

Hello!
I have been proudly and happily flying my MA2 for over 3 weeks now. Having previously flown the MM and the MA, I am used to both control apps, and DJI Fly was nothing to me.

HOWEVER, two very weird things happened today which I have never experienced.

1. As usual, I turned on the RC first, opened the Fly app, then turned the AC on (while on ground at point X) and waited for GPS lock, plenty of satellites, and for the home point to be set (the whole thing took about 30 secs I would say). After all that, I picked up the AC to move it to point Y, a meter away from point X. When I picked it up, I felt a strong vibration (much like a vibrating cellphone) and heard a noise (I would describe it as the noise you would hear when you rub a steel knife against a rusted iron plate). I saw no warnings, whatsoever, except for IMU Attitude Error which is because of me lifting the AC and moving it to point Y.

2. In the same flight, I lost connection with the aircraft, which isn't unusual, but this time around, the Fly app crashed and I had to re-open it. When I did so, it initially said said "AC not connected to RC", but then said "Home-point has been updated, please check it on the map". My heart skipped a beat, but I was relieved when I noticed that it was the same homepoint I initially set at X. When I looked at the flight logs, I actually saw two different ones- one until the app was disconnected and the other from when I restarted the app!!

I can't help but think about the worst; what would happen if the HP was updated at the then-current location of the AC!?

Would love to hear your experiences on both these issues, if you've ever encountered them.

Did you notice any movement of the propellers when you picked up the AC?

There are two primary types of motor used on drones (of all sizes). The brushless motors (BLDC) may have inbuilt sensors to detect the position of the rotor or sensor-less where a back electromotive force is measured instead to determine rotor position. The ESC (Electronic Speed Controller) handles the motor drive control requirements based on the input from the flight controller. On startup you may occasionally notice a vibration when an ESC is determining the position of its associated motor’s rotor. I’ve noticed it a few times on my M2Pro and usually accompanied by a metallic sounding noise.

A piece of grit in the motor could also cause this if the ESC is trying the above and the rotor is being restricted. Any significant obstruction and you would receive an overload error.

 

[Vaideeshwar]

Did you notice any movement of the propellers when you picked up the AC?

I picked it up after all the pre-flight calibrations were done (the gimbals, the props and the "DJI tone"). If you are talking about the propellers just changing their position due to gravity differential across them when I lifted the drone, maybe. But I noticed nothing unusual with the propellers whatsoever.

There are two primary types of motor used on drones (of all sizes). The brushless motors (BLDC) may have inbuilt sensors to detect the position of the rotor or sensor-less where a back electromotive force is measured instead to determine rotor position. The ESC (Electronic Speed Controller) handles the motor drive control requirements based on the input from the flight controller. On startup you may occasionally notice a vibration when an ESC is determining the position of its associated motor’s rotor. I’ve noticed it a few times on my M2Pro and usually accompanied by a metallic sounding noise.

I think I know what you mean by "metallic sounding noise". Would you describe it to be a low amplitude, intermittent, high-frequency squeak? If so, then no. This was pretty loud noise that I would describe to be "concerning". I tried to see if it happens again so I can record it, but no luck.

A piece of grit in the motor could also cause this if the ESC is trying the above and the rotor is being restricted. Any significant obstruction and you would receive an overload error.

No, I got no overload errors either. Only error I got was the IMU attitude error, which was because of me handling the drone during my attempt to reposition it.

Pretty unsettling stuff!

 

[fGene]

Okay, so, the "Intial HP" and the "Updated HP" are not significantly apart, and are pretty much the same spot where I took off from. At signal loss, the HP is the same as the Updated HP. All this is true.

I beleive someone in this forum once mentioned the home point sometimes gets updated twice, once on the ground, and second time in the air if the drone hovers above the landing pad for 10 seconds -- presumably to assist with precision landing using VPS. Could it be related to your case? Unfortunately, I don't remember where exactly I read this...

 

[Vaideeshwar]

I beleive someone in this forum once mentioned the home point sometimes gets updated twice, once on the ground, and second time in the air if the drone hovers above the landing pad for 10 seconds -- presumably to assist with precision landing using VPS. Could it be related to your case? Unfortunately, I don't remember where exactly I read this...

I remember reading it too, but no, I do not know of any HP update other than the original one, after which I got a notification. I took off after this notification and did not see any other HP-related notification post-take off.

However, I did receive the same notification after my app crashed mid-flight (pics uploaded), and was pleasantly surprised to find that the app adopted the original HP, and not the current location of the AC.

 

[Meta4]

Like mentioned in this picture, I got the "Home Point has been updated, please check it on the map" notification on my cellphone at about ths point after the app restart. I panicked because I thought the app was going to set the then-current location of the drone as the HP, but luckily it did not.

Looking at the actual flight data for both flights, the only Home Point updated message comes right on the initial takeoff.
There is no second message in the second flight and the stored home point stays the same.
Check for yourself:
1st flight: DJI Flight Log Viewer - PhantomHelp.com
2nd flight: DJI Flight Log Viewer - PhantomHelp.com

I beleive someone in this forum once mentioned the home point sometimes gets updated twice, once on the ground, and second time in the air if the drone hovers above the landing pad for 10 seconds -- presumably to assist with precision landing using VPS. Could it be related to your case? Unfortunately, I don't remember where exactly I read this...

The homepoint sometimes updates with better GPS data shortly after takeoff, but it is entirely GPS and has nothing to do with precision landing feature..
If you've observed it around the same time, that was just coincidence.

 

[Vaideeshwar]

Looking at the actual flight data for both flights, the only Home Point updated message comes right on the initial takeoff.
There is no second message in the second flight and the stored home point stays the same.

Firstly, thank you so much for looking at ny flight logs for me. Appreciate the help.

I saw the logs myself and didn't see an indication of HP being set, but I can swear that I got the "The homepoint has been updated, please check it in the map" notification right after I restarted the app. It is weird why it didn't show on the logs, but I am very positive that I heard it.

 

[Meta4]

I can swear that I got the "The homepoint has been updated, please check it in the map" notification right after I restarted the app. It is weird why it didn't show on the logs, but I am very positive that I heard it.

If you heard the message, it must have been a one-off glitch.
Your stored homepoint is secure .. DJI have made it that way since RTH depends on it if you lose signal.