Interesting conversation.. Why would the copter go into the toilet bowl effect? You would think, even if it can't figure out its orientation, shouldn't the gps hold it in one spot.. In my video with the toilet bowl effect, I just drop the controls at my lap, and, meanwhile, the circles get bigger, and the copter goes faster.. What would cause that? ..And why would rotating the compass 30 degrees, stop it?
Fixing DJI's Compass Problem
- Thread starter ianwood
- Start date
obiwan_pierogi said:
It's just caused by an inappropriate response to a perturbation from a setpoint - in this case a 2D location. A simplified explanation that ignores the learning capabilities of the FC - if the FC detects that it is drifting off location (wind, GPS drift etc.) it initiates corrective action - a restoring vector that it estimates will take it back to the target location. If that vector is in the wrong direction (offset by a fixed angle in this example), it will end up circling the target location. Depending on the gains in the control loop and the offset, those circles may increase or decrease in radius.
Does anyone else find it ironic that ianwood's request to stop talking about compass rotation in order to keep this thread on topic and uncluttered resulted in a sh*storm of pointless comments?... OK, not pointless, but you get my point.
landonkk said:
Yep... It's a regular Tolkien fest in here... trolls, flamers, and the occasional gollum. ::sarcasm::
sar104 said:
Perfect description of TBE. That should be a sticky all by itself. The only thing I would add is the incorrect vector happens as result of the FC initiating the corrective vector using the misaligned compass heading. That initiates yet another corrective action that is also misaligned and so on.
landonkk said:
Biting my tongue. I dismissed compass rotation in the very first post of this thread.
The thing that bothers me, is why a fellow vision 2 owner, who lives a couple of hundred miles North of me, and whose declination is a degree higher (about 18.5+)., why is it, he doesn't experience the TBE? And his compass is in the factory set position.. I have had the gps and the compass replaced, but my copter would continually slip into the TBE.. Could there be something else? Also, without turning the compass, my copter would skew left, if lined it up directly towards an object in the distance..
+1 for a matching problem in Tucson, AZ.
It did seem to begin after a few 'normal' flights. I had a hard landing, and then did the latest firmware update (3.02), and the first flight after notice about a 10 degree shift..
-Liam
It did seem to begin after a few 'normal' flights. I had a hard landing, and then did the latest firmware update (3.02), and the first flight after notice about a 10 degree shift..
-Liam
Read Here ------> viewtopic.php?f=19&t=11555obiwan_pierogi said:
Beta testers are presently waiting for beta firmware to retest (I assume) and we have all sent our Beta Test Flight Data to DJI.
DJI has a great opportunity to fix this frustrating problem
Anyone interested in Reading about DJI and the Beta testers should READ this first ------> viewtopic.php?f=19&t=11555
obiwan_pierogi said:
Your declination is high enough that you would normally see TBE and hooking. As for you neighbor not seeing it, please find out what firmware he is on. If it is the very first firmware from 2013, that might be a significant clue!
LiamFrederick said:
I thought the same and others have made similar claims. It is most likely though that during those first few flights we were so busy learning the Phantom, we were not flying it in ways that exhibit the issue and even when it did, we were too busy concentrating on flying it to notice. The compass is not typically effected by hard landings.
As far as I know, my fellow flyer has all the latest updates.. Anyways.. What I find unusual-- and I've posted it on here before-- is with my compass rotated, the hook changes direction, based on the direction my copter is traveling.. And I don't mean, as the person demonstrated by flying straight out, then, reversing the craft.. If I fly straight, in a Southerly direction, the copter hooks left, then from that point, if I turn the craft around, andimmediately fly straight in a Northerly direction, the copter hooks right.. Fly somewhere in the direction in between, and little to no hook.. How does that figure?
obiwan_pierogi said:
You are getting the odd results you are because the compass is not in the position the FC thinks it's in. Two of the three axes in the compass are skewed 30 degrees from where the FC thinks they are. Calibrating the compass will still allow it to resolve a relative heading but not one that is properly adjusted to its actual orientation. The FC is computing heading including attitude compensation assuming the compass is perpendicular to the craft. This is one of a dozen or more reasons rotating the compass is not recommended by DJI.
As for your friend, I'd be curious to see a video of his Phantom flying. Could you get him to run some of the tests we've been doing? Specifically, if he could post a video starting with a freshly charged battery, take off and using only elevator, fly forward fast for 40-50m and then let go allowing the Phantom to drift until it comes to a full stop. Must be done at the beginning of the flight.
obiwan_pierogi said:
I don't really notice TBE with my Phantoms, but the j-hook is VERY pronounced. When you guys say TBE, you mean that it hovers in a circle, right? If mine do, it is a very small circle, but like I said, my Phantoms fly "straight" about 15 degrees off and at the end of a run, drift about 20 feet to the left (at the beginning of a battery). I'm curious too....
Hi all
Just created an account to add myself to the long list of users experiencing the issue.
Phantom 2
NYC: -13,4 of magnitude declination
When I first used my phantom 2 after compass calibration, I noticed that it would drift to the right when I was trying to go straight. I first blamed it on the wind and my inexperience with the sticks.
I then did a calibration of the compass after installing a FPV system. The calibration was done in the worst possible conditions (lots of structure and steel around). And oh boy what happened next was scary. I started to notice my copter doing wide circles for no apparent reason. What I saw on my FPV scared the living hell out of me. I thought it was gonna capsize and fall like a stone.
I managed to land it without problem and went straight to google the issue and here I am.
I did all the updates, calibrated the sticks and the IMU (basic), and went far away from structures to do a compass calibration.
The TBE effect is gone but I am still not flying straight..
I dont want to move my compass though, so I am posting to stay up to date on the matter.
Thank you for trying to have DJI come up with a fix!
Just created an account to add myself to the long list of users experiencing the issue.
Phantom 2
NYC: -13,4 of magnitude declination
When I first used my phantom 2 after compass calibration, I noticed that it would drift to the right when I was trying to go straight. I first blamed it on the wind and my inexperience with the sticks.
I then did a calibration of the compass after installing a FPV system. The calibration was done in the worst possible conditions (lots of structure and steel around). And oh boy what happened next was scary. I started to notice my copter doing wide circles for no apparent reason. What I saw on my FPV scared the living hell out of me. I thought it was gonna capsize and fall like a stone.
I managed to land it without problem and went straight to google the issue and here I am.
I did all the updates, calibrated the sticks and the IMU (basic), and went far away from structures to do a compass calibration.
The TBE effect is gone but I am still not flying straight..
I dont want to move my compass though, so I am posting to stay up to date on the matter.
Thank you for trying to have DJI come up with a fix!
The way I see it, the compass just tells the brains, the direction it is pointed.. Rotating the compass shouldn't really screw up anything, other then deciding which direction is front.. I am extremely careful when I calibrate to make sure the compass is parallel to the Earth.. So with my compass rotated, when I do the second part of the calibration, by turning the copter on edge, I position is so one leg is slightly dipped down (to keep the compass in the same position, in relation to the ground, if it was attached in the factory set position) .. I know my fellow copter flyer is plagued with the major left hook, after a straight run, but he doesn't experience the TBE.. My toilet bowl effect, was upwards of 70 feet..
One thing I have noticed, is that if I do a straight run, then let go of the toggle, the copter will keep going straight ahead for a period of time.. This is fine, if there's no swing, one way or the other, but becomes very noticeable, when you're behind the copter and instead of carrying on straight, it makes a dramatic left or right hook, depending on declination.. Maybe there's something in their programing, that momentarily shuts the compass off, when you let go of the toggle.. Otherwise, wouldn't the craft naturally arc left, as you were flying in a straight line? I was thinking maybe precession plays a part, but counter rotating props should null that aspect.. However, I'm not sure if the craft may have a built in gyroscope, which could be sending the wrong message, because of precession.. I just don't know enough about how the electronics function on this craft, other than what I can observe for myself
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