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Drone not flying straight after crash and repair

DroneFilmmaker

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After crashing my drone a couple weeks ago, I flew it a few times, didn't notice any problems, and then decided to replace the rear hinges. I just got them put on on Friday and fired the drone up this morning. It flies, but it won't fly straight. It drifts to the right when flying forward and to the left when flying backward. When I stop it drifts a bit more and then stabilizes.

What I've done so far:

Cold IMU cal
Remote cal
Compass cal

Not sure what else could be wrong with it unless I fried the compass or IMU when resoldering the wires. Is there something on the main board that I could have damaged that would cause this?

Anyone have any ideas of other things to check?
 

Mel 08

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Are any of the legs slightly bent?
I would assume this would cause your problem
 

Dronason

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If it is the structure that changed (angle of motor b.e.) I would expect it flight straight but its attitude could be strange. Drifting as I understand your description could be more a compass issue (bad or calibration). I would first retry to recalibrate the compass in a totally metal free environment, in a remote area with no metal on you and strictly following the procedure.
Last but worst would be a sensor failure but then you would probably get error message.
 

DroneFilmmaker

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Are any of the legs slightly bent?
I would assume this would cause your problem
It seems like one of the rear legs is bent up a tiny amount (maybe a couple mm), but I'm not sure why that would make it drift. They're generally pretty resilient to those kind of changes.
 

DroneFilmmaker

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If it is the structure that changed (angle of motor b.e.) I would expect it flight straight but its attitude could be strange. Drifting as I understand your description could be more a compass issue (bad or calibration). I would first retry to recalibrate the compass in a totally metal free environment, in a remote area with no metal on you and strictly following the procedure.
Last but worst would be a sensor failure but then you would probably get error message.
Hmm, I calibrated the compass in an open field but it was only maybe 50-60 feet from a power distribution line. Calibrated it the way it showed on the screen. Maybe I should try in a more remote field. Do you know how far you need to move the controller away from the drone when doing the compass calibration? I was thinking maybe a fried sensor, but I was thinking that should give an error.
 

old man mavic

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have you measured between the motor spindle centers front to rear and diagonally to check if its all square after your repair ,if there is an issue with the ESC's then that would make it fly to one side or the other ,as its only motor speed that controls direction of drone
 

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No clue what kind of drone do you own, but for dji drones the controller sticks calibration helps, neither compass or IMU controls your flight direction (apart of RTH) but your controller sticks ;) at the moment they are not balanced specially at the default middle position you can encounter drifting or spinning even when you do not touch them
 
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Dronason

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Hmm, I calibrated the compass in an open field but it was only maybe 50-60 feet from a power distribution line. Calibrated it the way it showed on the screen. Maybe I should try in a more remote field. Do you know how far you need to move the controller away from the drone when doing the compass calibration? I was thinking maybe a fried sensor, but I was thinking that should give an error.
4-6 feet should be fine. The description where you calibrate it sounds good. You can retry it but probably not the main issue.
By chance there are other good suggestions.
 
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DroneFilmmaker

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have you measured between the motor spindle centers front to rear and diagonally to check if its all square after your repair ,if there is an issue with the ESC's then that would make it fly to one side or the other ,as its only motor speed that controls direction of drone
I guess I didn't make myself clear. The drone's heading stays the same, but it flies forward and to the right at the same time while maintaining its heading.
 

WithTheBirds

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I guess I didn't make myself clear. The drone's heading stays the same, but it flies forward and to the right at the same time while maintaining its heading.
Well then you have a simple alignment issue with your repair work, or, and this would be less likely- a monumental balance issue.

Not unlike a vehicle that has had nice panel work after a collision but the chassis is bent. It’s following the road but looks scary comming towards you.
 

DroneFilmmaker

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No clue what kind of drone do you own, but for dji drones the controller sticks calibration helps, neither compass or IMU controls your flight direction (apart of RTH) but your controller sticks ;) at the moment they are not balanced specially at the default middle position you can encounter drifting or spinning even when you do not touch them
DJI Mavic Pro of course. And as I said in my original post, I already did a controller calibration.
 

DroneFilmmaker

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Well then you have a simple alignment issue with your repair work, or, and this would be less likely- a monumental balance issue.

Not unlike a vehicle that has had nice panel work after a collision but the chassis is bent. It’s following the road but looks scary comming towards you.
Hmm, could be. Not sure how it could be miss-aligned. I'll have to check.
 

old man mavic

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lets get something cleared up my friend ,if the drone is flying to the right ,forwards or left backwards then it is not maintaining its heading it vearing one way or the other
if you aimed it towards a fixed point some 300ft away then it should just fly straight towards that point if no other stick input is made apart from forwards
if the drone is flying as if its crabbed to one side but still going straight then that is a issue with alignment of the thrust direction of the props relative to the center of gravity of the drone
 

DroneFilmmaker

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lets get something cleared up my friend ,if the drone is flying to the right ,forwards or left backwards then it is not maintaining its heading it vearing one way or the other
if you aimed it towards a fixed point some 300ft away then it should just fly straight towards that point if no other stick input is made apart from forwards
if the drone is flying as if its crabbed to one side but still going straight then that is a issue with alignment of the thrust direction of the props relative to the center of gravity of the drone
Ok, maybe my terminology was lacking. The drone keeps pointing the same way. In other words it is NOT yawing. But it drifts to the side as if the right stick was being pushed to the right as well as forward. The "nose" of the aircraft remains pointed in it's original direction however.
 
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old man mavic

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thank you that makes more sense i am assuming your using right stick for forwards and reverse flight and also to bank left or right ,then the only way the drone will drift is if there is some slight side ways input from the right stick as it is flying does it drift when its hovering i think you said you had calibrated the sticks maybe the right one is not quite centered also check your expo settings for sensitivity the only other thing is the ESC board getting an incorrect signal from the IMU,and the motors causing a speed difference between the two on the right side compared to the two left motors
 

DroneFilmmaker

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thank you that makes more sense i am assuming your using right stick for forwards and reverse flight and also to bank left or right ,then the only way the drone will drift is if there is some slight side ways input from the right stick as it is flying does it drift when its hovering i think you said you had calibrated the sticks maybe the right one is not quite centered also check your expo settings for sensitivity the only other thing is the ESC board getting an incorrect signal from the IMU,and the motors causing a speed difference between the two on the right side compared to the two left motors
I played back the flights with stick view on and there is no sideways input. It's pretty solid while hovering so that makes it even more strange.
 

DroneFilmmaker

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I just did some more testing and found some VERY strange things.

To start with I had found that it drifts to the right when flying forwards and to the left when flying backward. However, in all my test flights I was flying it in the same orientation.

This morning I decided to fly it the opposite way from my take-off point. When pointing in the opposite direction it drifts LEFT when flying forward and RIGHT when flying backward. So if the drone is rotated 180 degrees, the compass direction of the drift does NOT rotate with the drone but remains the same for forwards and backward flight.

To explain that a little more clearly. (these headings are not the actual headings from my test flights). When the drone is oriented so that the nose is facing WEST the drone drifts to the NORTH when flying forwards and to the SOUTH when flying backward. I expected that when the drone's nose was pointing EAST that it would drift to the SOUTH when flying forwards and to the NORTH when flying backward. However, this is not the case. When the drone is oriented with its nose pointed EAST it STILL drifts NORTH when flying forwards and SOUTH when flying backward.

In other words, the direction of the drift is NOT tied to the direction the nose of the drone is pointing.

To confirm this, I flew the drone perpendicular to my previous flight paths. Instead of drifting, it stayed dead on course.

Now what does this mean? I'm not sure. It couldn't be a motor alignment problem, ESC problem, or an IMU problem as these would all make the direction of drift rotate with the drone. I can see how a compass problem could act this way but I would think that would cause the drone to yaw rather than move to the side. The only other options I can think of are #1 a problem with the GPS unit (never heard of that) or a magnetic anomaly here that has appeared since I last flew here about 3 weeks ago.

If anyone has any thoughts on what might be going on I would love to hear them.
 

old man mavic

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there is one thing the AC may have become magnetised when you did the repair and would then need a degauser to remove it ,if you have got a compass set a pointer to magnetic North on a none metalic surface no metal or rebar in the ground and then point the drone in the same direction and once the drone has connected to the RC and device ,then if all is well the arrow in the radar like icon should point to the small N at the edge, and then when you unlock the compass icon on the edge of the small map, the drone direction indicator should point the same way as the radar arrow
 

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I just did some more testing and found some VERY strange things.

To start with I had found that it drifts to the right when flying forwards and to the left when flying backward. However, in all my test flights I was flying it in the same orientation.

This morning I decided to fly it the opposite way from my take-off point. When pointing in the opposite direction it drifts LEFT when flying forward and RIGHT when flying backward. So if the drone is rotated 180 degrees, the compass direction of the drift does NOT rotate with the drone but remains the same for forwards and backward flight.

To explain that a little more clearly. (these headings are not the actual headings from my test flights). When the drone is oriented so that the nose is facing WEST the drone drifts to the NORTH when flying forwards and to the SOUTH when flying backward. I expected that when the drone's nose was pointing EAST that it would drift to the SOUTH when flying forwards and to the NORTH when flying backward. However, this is not the case. When the drone is oriented with its nose pointed EAST it STILL drifts NORTH when flying forwards and SOUTH when flying backward.

In other words, the direction of the drift is NOT tied to the direction the nose of the drone is pointing.

To confirm this, I flew the drone perpendicular to my previous flight paths. Instead of drifting, it stayed dead on course.

Now what does this mean? I'm not sure. It couldn't be a motor alignment problem, ESC problem, or an IMU problem as these would all make the direction of drift rotate with the drone. I can see how a compass problem could act this way but I would think that would cause the drone to yaw rather than move to the side. The only other options I can think of are #1 a problem with the GPS unit (never heard of that) or a magnetic anomaly here that has appeared since I last flew here about 3 weeks ago.

If anyone has any thoughts on what might be going on I would love to hear them.
Yeah that's what mine seems to be doing.

I have videos that show that it flew correctly when I first got it.

So the problem has happened since then.
 

DroneFilmmaker

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there is one thing the AC may have become magnetised when you did the repair and would then need a degauser to remove it ,if you have got a compass set a pointer to magnetic North on a none metalic surface no metal or rebar in the ground and then point the drone in the same direction and once the drone has connected to the RC and device ,then if all is well the arrow in the radar like icon should point to the small N at the edge, and then when you unlock the compass icon on the edge of the small map, the drone direction indicator should point the same way as the radar arrow
Tried that, didn't have a compass handy at the moment, but it looked pretty spot on. (I know where north is in our valley) I'll have to recheck with a compass.
 
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