Y6 Yaw Control Problem

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Y6 Yaw Control Problem

Postby epyonxero » Sat Nov 03, 2012 6:45 pm

I had a new issue pop up on my Y6 with AQ 6.6 R33. For the last couple of flights the vehicle is losing yaw control during forward flight and yawing in a CW direction. If I try to correct it I get no response from the vehicle until I enter a hover and then the controller seems to catch up to the yaw command moves to the correct heading, its a delayed reaction. This happens in ALT Hold and Manual.

From the logs it looks like the controller is fighting a CW yaw force right from the beginning and in forward flight it hits a limit for which it cant correct anymore. But why? All my motors seems to be operating normally and they are mounted level.


Log File:
http://dl.dropbox.com/u/2317679/027-AQL.LOG
Attachments
Yaw Problem.png
Yaw Graph
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Re: Y6 Yaw Control Problem

Postby Kisssys » Sat Nov 03, 2012 7:58 pm

You may fix the problem with changing the yaw PID's, the defaults are too low to fight a machine that is not neutrally stable.

Plot your motor outputs and you will see some motors are always working harder than others. Chances are those are the ones that are trying to correct your constant yawing in one direction. On a quad or hexa you can rotate a motor slightly to create the added yaw you need so all motors in a level hover put out the same power. If you could apply the same power to all motors and it would come up level and not yaw, you are neutrally stable.

I have not looked at a Y6 to know whether you can solve it mechanically by rotating both engines. I'm not sure if the top and bottom engine cancel each other. If they do I guess you have to shim something.
Steve
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Re: Y6 Yaw Control Problem

Postby bn999 » Sun Nov 04, 2012 1:52 pm

As Steve said, your best best is to get the machine closer to being yaw neutrally stable. However, a quick fix will be to increase one or both of these parameters:

YAW_RTE_IM
YAW_RTE_OM
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Re: Y6 Yaw Control Problem

Postby epyonxero » Thu Nov 08, 2012 1:01 am

Ok, Ive been looking at my lastest flight logs and some older flight logs from before I had this problem and I cant figure out why my Y6 wants to yaw clockwise, Ive been using this frame, PID set, and mixing table for months without this problem. The difference in PWM outputs between motors makes sense for a FC thats trying to compensate for uncommanded yaw. The higher PWM motors are CW rotating and the lower output motors are all CCW. One thing thats seems strange is that although the output in the negative yaw group is increasing to try to stop the CW yaw, it never seems to max out and the positive yaw group never bottoms out.
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Re: Y6 Yaw Control Problem

Postby Kisssys » Thu Nov 08, 2012 3:24 am

The max correction is set by the PID settings. Have you tried to increase YAW_RTE_IM and YAW_RTE_OM as Bill suggested.

I have YAW_RTE_IM = 150 YAW_RTE_OM = 300 on my quad.

If it's been working fine it maybe it's as simple as a slipping prop or a slight twist in motor position. It doesn't take much if the above outputs are too low.
Steve
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