HELP! Mini 2 moving on its own!

[KJ-Mini2]

You have to be careful too much heat will lift the pad. Thats the Best soldering iron for drones! IMO

Hi sorry to ping you but I just had a question, I saw some people mention that it could have just been radio interference messing with the drone, could that be possible? I know when I was landing it that it was working completely fine again once it was near me and when I hovered it and moved it around inside the house it listened perfectly fine to me.

 

[Cafguy]

Ping anytime you like! That is a possibility Sure BUT you do have an arm problem that needs attention. It is very possible that interference may be the cause this particular problem however the most obvious explanation usually ends up solving the problem. Not having been there and not seeing what happened I would say most likely the broken arm is the culprit and if it turns out that it was interference ( Maybe - not probable tho ) you have still fixed a major problem that will end up with your drone loosing the arm in flight and crashing. Occums Razor tells me the problem is with the arm.

 

[KJ-Mini2]

Ping anytime you like! That is a possibility Sure BUT you do have an arm problem that needs attention. It is very possible that interference may be the cause this particular problem however the most obvious explanation usually ends up solving the problem. Not having been there and not seeing what happened I would say most likely the broken arm is the culprit and if it turns out that it was interference ( Maybe - not probable tho ) you have still fixed a major problem that will end up with your drone loosing the arm in flight and crashing. Occums Razor tells me the problem is with the arm.

Yep, thanks, I'll fix the arm for sure. I found a friend at church yesterday who knows how to solder so I think I've got a job for him, he's got some experience with it for sure.

 

[KJ-Mini2]

Mini2" data-source="post: 1639476" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

Yep, thanks, I'll fix the arm for sure. I found a friend at church yesterday who knows how to solder so I think I've got a job for him, he's got some experience with it for sure.

I flew it again today very close to me so I couldn't really lose it or anything could go wrong.
Two things: there were some weird connection losses, and at one point it was moving the wrong way after I used both joysticks at the same time.
There were movements and changes of up to 0.5m/s, it was pretty windy though.

Is that normal and should I send in the log?

 

[Yorkshire_Pud]

The log is always useful though it may be split into parts.
Have you tried the test flight of post 30 ?

 

[Cafguy]

I would post the log, and read post 30 I agree with the tripod mode comm? I forgot about the vid sorry. The antenna could have been loosened when the Drone crashed. NOW remember-!! that the antenna wires run through the front arms of the drone.is one of those damaged as well. These drones can wire bust connections loose in a crash easier than most drones just the nature of having all that stuff crammed into a plastic shell.

 

[KJ-Mini2]

I would post the log, and read post 30 I agree with the tripod mode comm? I forgot about the vid sorry. The antenna could have been loosened when the Drone crashed. NOW remember-!! that the antenna wires run through the front arms of the drone.is one of those damaged as well. These drones can wire bust connections loose in a crash easier than most drones just the nature of having all that stuff crammed into a plastic shell.

From what I know the front arms are doing just fine, the connection also worked for the first few weeks perfectly after the crash and there were no incidents since then.

DJI Flight Log Viewer - PhantomHelp.com

 

[KJ-Mini2]

The log is always useful though it may be split into parts.
Have you tried the test flight of post 30 ?

Not tried that yet, probably tomorrow I don't want to bother the neighbours right now...

 

[Droning on and on...]

Mini2" data-source="post: 1639462" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

Hi sorry to ping you but I just had a question, I saw some people mention that it could have just been radio interference messing with the drone, could that be possible? I know when I was landing it that it was working completely fine again once it was near me and when I hovered it and moved it around inside the house it listened perfectly fine to me.

In the "Occam's Razor" hierarchy, I'd say RF interference is pretty low on the list. Far more likely some flexing around that repaired joint causing a lateral component of thrust (as @Cafguy described in post #53), confusing the Flight Controller as it tries to compensate assuming all the thrust is going in the designed direction.

 

[KJ-Mini2]

In the "Occam's Razor" hierarchy, I'd say RF interference is pretty low on the list. Far more likely some flexing around that repaired joint causing a lateral component of thrust (as @Cafguy described), confusing the Flight Controller as it tries to compensate assuming all the thrust is going in the designed direction.

Sounds like you know what you're talking about, I'll take it from someone who knows quite a bit more than I do, thanks!

 

[Droning on and on...]

Mini2" data-source="post: 1639583" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

Sounds like you know what you're talking about, I'll take it from someone who knows quite a bit more than I do, thanks!

Not really, but I play a Doctor on TV

The thing about glue is, if repeatedly stressed and flexed back and forth, it will loosen more and more and eventually fail. Use a more flexible glue, and it won't be rigid enough to duplicate the stiffness of the original material.

If one insists on repairing a crack like this rather than just replacing the component, you're better off doing a "plastic weld" rather than gluing. And don't kludge such an operation with a $15 soldering iron... Get a real plastic welding kit.

Or just replace the arm. Cheaper

 

[KJ-Mini2]

Not really, but I play a Doctor on TV

The thing about glue is, if repeatedly stressed and flexed back and forth, it will loosen more and more and eventually fail. Use a more flexible glue, and it won't be rigid enough to duplicate the stiffness of the original material.

If one insists on repairing a crack like this rather than just replacing the component, you're better off doing a "plastic weld" rather than gluing. And don't kludge such an operation with a $15 soldering iron... Get a real plastic welding kit.

Or just replace the arm. Cheaper

Yeah the problem is it's a middle shell replacement that would be needed. But I noticed a pattern in that weird movement in the most recent test flight that, I think, indicates it's not the arm but something with the connection. Not only did the drone and controller have terrible connection in flight, I noticed that (this sentence is even hard for me to crunch so good luck

a) I used my right stick.
I didn't stop using the right stick and used the left stick.
I continued with my left stick and let go of my right stick.
b) I used the right stick again in a different direction than before, all while still using my left stick.
The drone moved in the same direction as at the beginning: in a.
I let go of my left stick.
I used my right stick in the same direction as in b, so different to a, now without touching the left stick.
The drone moved the right way.

Any ideas?

(Maybe hold the controller while reading the steps, I think this is pretty close to what happened, then maybe you can "feel" it. Any ideas about that?)

I only noticed this once but I think I only tried this once too, so...

 

[Droning on and on...]

The reason I'm not warming up to the disconnection theory is it's contrary to expected behavior if there is a disconnect, or weak signal.

This is not an analog system where signal characteristics can cause error in the interpretation of proportional control. It is pure digital, with various error correction algorithms in use, and the nature of this type of transmission is all-or-nothing – the Flight Controller either gets a fully decoded, correct representation of control inputs, or no control information at all because the bit errors due to weak signal can't be corrected.

In such a case, the drone will stop and hover in place, using either GPS or VPS – depending on AGL, to hold position. After some delay (in the specs, I think 10 seconds), it will initiate Failsafe Return To Home, and flight behavior will be quite controlled (automated) and predictable.

There's no situation I can imagine where, with signal/connection issues, the drone will move significantly in random, uncommanded directions.

A disconnect can be forced simply by turning off the RC when the drone is in-flight. If you try this, you will see the drone brake, hold position for a short period, then execute the Failsafe RTH procedure as specified in the manual. It will not start flying in any direction at all upon disconnect – only after the Failsafe RTH kicks in.

 

[KJ-Mini2]

The reason I'm not warming up to the disconnection theory is it's contrary to expected behavior if there is a disconnect, or weak signal.

This is not an analog system where signal characteristics can cause error in the interpretation of proportional control. It is pure digital, with various error correction algorithms in use, and the nature of this type of transmission is all-or-nothing – the Flight Controller either gets a fully decoded, correct representation of control inputs, or no control information at all because the bit errors due to weak signal can't be corrected.

In such a case, the drone will stop and hover in place, using either GPS or VPS – depending on AGL, to hold position. After some delay (in the specs, I think 10 seconds), it will initiate Failsafe Return To Home, and flight behavior will be quite controlled (automated) and predictable.

There's no situation I can imagine where, with signal/connection issues, the drone will move significantly in random, uncommanded directions.

A disconnect can be forced simply by turning off the RC when the drone is in-flight. If you try this, you will see the drone brake, hold position for a short period, then execute the Failsafe RTH procedure as specified in the manual. It will not start flying in any direction at all upon disconnect – only after the Failsafe RTH kicks in.

That's why I'm wondering, it's not very random. It seemed random but now that I looked at it it just followed the exact same command as before, almost as if there was a software issue which would completely change everything

 

[Droning on and on...]

Mini2" data-source="post: 1640130" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

That's why I'm wondering, it's not very random. It seemed random but now that I looked at it it just followed the exact same command as before, almost as if there was a software issue which would completely change everything

So I'm not completely ruling that out (firmware bug). You certainly might have stumbled across some corner case that others aren't, hence only you have consistently encountered this.

Again, however, Occam's Razor. Flexing around that crack at the root of the arm is a good explanation for what your seeing in terms of un-commanded behavior. Connection issues do not, and the fact that others aren't having this problem points to what's different about your drone.

Answer, the glue repaired, cracked-at-the-root arm.

 

[KJ-Mini2]

So I'm not completely ruling that out (firmware bug). You certainly might have stumbled across some corner case that others aren't, hence only you have consistently encountered this.

Again, however, Occam's Razor. Flexing around that crack at the root of the arm is a good explanation for what your seeing in terms of un-commanded behavior. Connection issues do not, and the fact that others aren't having this problem points to what's different about your drone.

Answer, the glue repaired, cracked-at-the-root arm.

Update, just came back from vacation with some friends and flew the drone maybe about two hours in a safe testing environment over three days and didn't notice a single significant issue in flight.