On a Y6 setup a small right yaw command makes the Muticopter yaw left.

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Arducoper NG or ACM?
Arducopter2

What steps will reproduce the problem?
1.Install 2.0.49 in a Y6 cofiguratien 
2.Give small right yaw correction control input 
3.The Arducopter will turn left

What is the expected output? What do you see instead?
I expect the Arducopter to turn right if I give the right command. I see it 
turning left (and very fast) 

What version of the product are you using? On what operating system?
At this moment 2.0.49. I saw the issue in 2.0.46. In 2.0.38 all was OK. On the 
forum somebody reported 2.0.42 was OK also.

Please provide any additional information below.

(copy of forum message)

I'm flying a Y6 configuration consisting of APM, PAN, compass, sonar, Xbee, 
Turnigy Plush 25A, RCTimer 2836 kv750, APC 11x4.7. I started with version 
2.0.38 about three months ago. It flew well. I tried to upgrade to 2.0.41 but 
could not get it operational.

    In the end of August I crashed the Arducopter due to a malfunctioning motor. Last month I build a new one and started to fly with 2.0.46. Last week 2.0.48 and since this morning 2.0.49.

    It took me some time to get the Arducopter flyng with 2.0.46/48. Reason: somewhere after 2.0.38 the rotation directon of some motors was changed.

    After adjusting direction of the motors de Arducopter was operational again. Behaved correctly on pitch and roll, but not on yaw. Turning to the left is OK. But turning to the right starts with an uncontrolled turn to the left. Giving more right yaw input makes the Y6 turn to the right at last. But small correctional commands to the right cannot be given. 

    This morning I changed the 2.0.38 code to support the prop directions of 2.0.49 and loaded it in the Arducopter. Test flying: no problem with yaw..

    The difference between the code of .38 and .49 is that in .38  the power of the top motors is decreased to 92% (0,92) of the power of the bottom motors. This factor is now disappeared.

    Entering this factor in the code againg solved the yaw problem almost. In fact, for my configuration 90% (0.90) is the correct factor.

    Yaw to the right is somewhat slower than to the left but I am not longer surprised with a Y6 turning the wrong way.

However, since the code in 42 seems to work according to another forum member 
and there is apart from a clean-up no dig=feerence in the code, I think it is 
not the real solution.

By the way: I understood that a Y6 frame is not avalable to the development 
team. I am quit willng to test a solution. Or if you can give me a hind where 
to start searching in the code to help solving the issue.

Original issue reported on code.google.com by willy.sw...@gmail.com on 17 Oct 2011 at 5:30

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Check out the MultiWii project. They have a lot of experience with Y6 mixing. 
That's what Max was using when he flipped the motors to the new config. MW 
doesn't use a scaling factor. 

Whatever you want to try, I'm more than willing to help!
Jason

Original comment by jasonshort on 17 Oct 2011 at 5:47

• Changed state: Accepted

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Just read your headline: a small right yaw command makes the Muticopter yaw left
This is a frame issue. Your motors are not aligned properly and have a natural 
bias to turn left.
Jason

Original comment by jasonshort on 29 Oct 2011 at 9:05

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I don't believe this is a frame issue. If I'm hoovering the Y6 it is completely 
stable on yaw and not slowly turning right or left. 
A second reason is that on my Y6 an CW and a CCW motor are mounted 
back-to-back, If one is misaligned, te other is also. They should, I think, 
compensate each other.
I only have the yawing issue if I give a small right command on the transmitter.

A reason for this behavior can be that the 6 motors are not identical. I'm 
using RCTimer 2836-750 motors and I have the feeling that the are not 
identical. I still have not figured out how to trace a faulty motor in an Y6 
configuration. That's why I first forwarded the question on the forum, to find 
out if there are others users with the same issue. And there is at least one.

I solved the issue by changing the code of motors-y6 and inserting the 
TOP-BOTTOM-RATIO factor again. Tuning it to 0.90 made the Y6 reacting properly 
to yaw ommands.

By the way: in the code the octo-quad configuration is still using the 
TOP-BOTTOM-RATIO.

I can start a new threath on the forum to find out if it is a frame/motor issue 
or a TOP-BOTTOM-RATIO software issue.

Original comment by willy.sw...@gmail.com on 30 Oct 2011 at 8:53

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I consider motor configurations frame issues. When you are not yawing your are 
in "Hold" mode. When you yaw, even in the slightest, you are in rate controlled 
yaw mode. If you just barely move the Yaw, you are commanding it to rotate at a 
 very slow rate. If the tendency to rotate left is higher than the motor output 
to rotate right, it will go backwards. 
Please post your fix and I'll update the frame definition.
Jason

Original comment by jasonshort on 30 Oct 2011 at 4:53

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Attached you find the file with the changes I made. I also changed the 
commented part of the code. If you use it, the motors have the same rotation 
direction as in 49 and not the "old" 38 directions.

I am testing to see if it is possible to misalign the frame in such a way that 
the issue comes back, after tuning the top-bottom ratio. I'm still working on 
that.

Original comment by willy.sw...@gmail.com on 31 Oct 2011 at 10:10

Attachments:

• motors_y6-wws.pde

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I misaligned one motorset a few degrees. Made no difference.

I checked the alignment of te Motors again. Removed all (possible) slack out of 
the frame. All motors are now checked to be straight mounted.

Started with TOP-BOTTOM_RATIO of 1.00. The issue reappeared. Changed the e 
ratio to 0.92. Issue almost disappeared. 0.90: issue disappeared completely.

Up to now I flew about 10 packs with this setting. Beheaviour of roll, pitch 
and yaw is consistent during all flights.

So, I think the TOP-BOTTOM_RATIO parameter is required for a Y6 configuration.

Original comment by willy.sw...@gmail.com on 2 Nov 2011 at 10:00

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made the change to .50
Thanks!
Jason

Original comment by jasonshort on 6 Nov 2011 at 3:58

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Original comment by jasonshort on 6 Nov 2011 at 3:58

• Changed state: Fixed