Vision: erratic flying mystery *video*

[WesCotten]

Hi all,

Been having a major issue ever since I took my prop guards off 3 months ago. The Vision is now flying in a very unstable manner when idling in midair. I can't shoot stable video or even fly it safely in this condition. Here are the steps I took to diagnose and attempt repairs...

- Took off prop guards, erratic flying began.
- Compass calibration had no effect, nor did advanced calibration through connecting via computer. The compass figures were well within the norm.
- Tested again and determined erratic flying occurred in both GPS and ATTI modes.
- Read a suggestion to replace the bearings in the motors. Ordered new bearings, opened the Phantom up but could not get old bearings out, slightly damaging the old motors as a result.
- Ordered $200.00 T-Motor Anti-Gravity replacement motors. Learned how to solder. Installed the new motors (correctly done for the self-tightening props), closed up the drone and tested. Phantom flew exactly as before, same erratic pitching and drifting.
- Updated all firmware in drone, controller and software updates to iPhone app with latest versions. Performed advanced calibration again.
- Phantom Vision continues to fly erratically as before in both GPS and ATTI modes and none of the motors are unusually hot to the touch.

Here's a video I shot of it loitering in mid-air after I installed the Anti-Gravity motors. I was not touching the controls, I had placed the controller on the ground while I shot the video. As you can see, it started to drift back towards the house and I had to drop the camera to grab the controller to bring it down...

https://vimeo.com/104444344

Getting pretty frustrated now and approaching my wit's end. Does anybody have any suggestions as to the problem and how I might fix it other than what I have already tried?

Thanks in advance,

- C

 

[noiseboy72]

It looks like the gains are incorrect. I think they are too high, but I can never remember which way round it is to lower the sensitivity and prevent it from over correcting.

Horizontal drift of 2M is quite normal, particularly at low level, where ground effect will tend to move it around. Get it up to 20' in clear air and see what happens.

 

[WesCotten]

Here are my current gains settings...

Basic: 120% Pitch, 120% Roll, 120% Yaw, 120% Vertical
Attitude: 200% Pitch, 200% Roll

Any suggestions for adjusted settings (based on the video)?

 

[BManCan]

Have you checked that your props are balanced?

 

[westray]

I see that in your original post that you removed prop gaurds.Did you use the same screws for the motors that you took out of the prop gaurds?If you did then this can damage the motors as they are too long.

 

[ProfessorStein]

I had the same thought, westray... but usually that "damage" usually completely destroys the motor, so I dismissed it. I suppose it's possible that the screws may have just sorta damaged the motor... worth a look.

 

[WesCotten]

I just double-checked and I did put the correct, shortened screws back in after taking off the guards. Good suggestion, and I'm glad I didn't make that mistake.

The props are balanced.

Still interested in messing with the gains. Any suggestions on how to mess aroudn with that?

 

[ted35]

I noticed on your video that your stickers aren't lined up. Is it possible the shell was rotated when reassembled? Since the GPS is attached to the shell it should be "facing forward" so that the main board and GPS don't have conflicting directional inputs. Just a thought.

 

[ProfessorStein]

Really? Never heard that one before, but it sort of makes sense.
Though... since he's getting rise-n-dive, and not just lateral drift, seems like something more than the GPS is involved. But who knows. Nice catch on the labels. Missed that.

 

[westray]

I agree with ted35 that the problem is due to the top cover not being replaced in the correct orientation.

 

[brushlesheaven]

One or more motors need bearing replacement.
They are not the best quality components out of the box.
I had the same situation and after replacing 2 motors bearings, calibrating, all was like brand new...
Easy fix and bearings are cheep on E-bay.
Spin the motors dry with your fingers, fast, one at the time, compare the sound you hear as they spin and replace the one that sounds different than others.
It worked for me....

 

[ProfessorStein]

Since the GPS is attached to the shell it should be "facing forward" so that the main board and GPS don't have conflicting directional inputs. Just a thought.

So... how do you know what direction the GPS is "facing"? It's a round PCB. Assume it has something to do with the side the leads/wires are coming off of it?

 

[RandyCPI]

Wes,
Did you find any solution(s) for this issue?
Sounds similar to the erratic behavior of my vision 2 after some different changes, wondering if NAZA has some sort of method of "learning" function based on normal flight such that when changes are made, we experience this erratic flight.

mine is loosing altitude like up to 30 feet in 20 seconds, sometimes resulting in a soft to hard bounce landing if allowed, and sometimes phantom will recover sometimes.

Did Gains changes help at all?

RR

 

[westray]

The gps is located in the top cover.If the top cover is replaced in the wrong orientation then a conflict is caused to the information the controller is receiving.This will result in erratic flight.The top cover MUST be replaced in the correct position(slight recess on top arms matching with recess on lower body) for quad to fly correctly.

 

[noiseboy72]

I'm interested on the GPS info. I thought GPS was a single omnidirectional aerial system, using Doppler shift for speed and relative timing information for position. How does orientation affect it? Are there other sensors built into the unit as well?

 

[ProfessorStein]

Yes... the more I've read, I'm feeling like this is a non-starter.

The Phantom GPS puck (the part mounted inside the top of the shell) is omnidirectional and knows nothing about orientation. It just triangulates between satellites, wherever they may be in the sky, to determine it's own coordinates. Then it passes that information to the main board and the board determines what direction the Phantom needs to travel to reach a different set of coordinates (through math calculations, not GPS), and queries the compass to see which direction that might be given the bird's current orientation.

But the GPS puck, itself, SHOULDN'T care how it's oriented. Unless I'm missing something.

 

[westray]

To put an end to this why don't you turn the top cover to where it should be and see if it makes a difference.

 

[WesCotten]

Ted, thanks for pointing out the misaligned stickers. I somehow didn't catch that and just put the shell back on correctly. Still having the same problem but now my wifi will connect to phantom but the app is suddenly saying the connection is failing.

Think I knocked something loose?

-C

P.S. Somebody PMed and gave me some new gains settings to try. Helped a little. Still popping around, but it seems to have calmed the drift. Still. wouldn't be usable for stable video. Doesn't matter at the moment since I can't get the video working anyway.