How to reverse yaw control on Tri-copter

I have serious problem how to configure my tricopter (2.0.39). Roll and pitch are correct. Yaw(rudder aka tail servo) was incorect thus i reversed RC channel via MAVlnk (btw i don't understand why dip switches are not enabled anymore in ACM...)

Now the servo moves correct according to radio stick movement but when i do yaw movement of frame by hand servo moves incorrectly - by this 'correction' frame would start spin infinitely.

How can i reverse this?

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        • It sounds to me like a compass issue. It took me a few times to get the calibration right.

          Or motor direction or fail safes. The fail safes are only good once everything else is working. I would look at disabling them first, then check motor direction (no propellors). If it's trying to RTL when you turn off the Tx it will not rest but try to go to 100m first. You can set this FS to do nothing or land.

          The check the sensor setting on the MP, and see if they tell the truth. 

          APM has lots of things to go wrong but lots of uses too.

          Don't give up on APMs.

          Cheers. 

        • TRied everything, looks like I will have to go back to my KK2 board for the tricopter. Ive just bought all the gear for a quad so I will swith the APM2.5 over to the quad build. Might go for the NAZA on my tricopter.

          • Make sure everything is hooked up correctly and you have calibrated EVERYTHING (radio, compass, accelerometer).  Get the servo working correctly via your radio input first.  If APM is not applying the yaw correction correctly then go to RC7_Rev and change its value from 1 to -1 or vice versa.  If you don't see a change in yaw correction then something else is wrong.  Make sure you have flashed it with Tricopter and the latest firmware.  I just did a tri today and it was all reversed but I got the radio right then rc7_rev changed and all was well.  Good luck.  

            • Thanks Marcus, I will try again starting from the flashing with tricopter firmware.  Something I did notice previously when I used the flashing Wizard (in MP) was that there was no option for Tricopter. But when I flashed manually the option for tricopter came back.

  • How do you reverse the yaw on the APM 2.5 using the mission planner?

  • Just to report back and confirm, this fix works very well for me. Yaw works correctly and there are no apparent problems with the tri. Glad to finally get it flying on APM. Previously i was trying to get it to fly good on a kkmulticopter board which was a disaster compared to APM. Very smooth, im pleased.

  • After tons of googling, searching the forums and on and on I really found no answer to this. It seems it would be really simple, the best i could find was respondents suggesting to reverse channel 4 within the planner. As explained above this reverses the servo but the yaw correction from the APM remains incorrect.

     

    Maybe reversing a channel in the APM works for planes and such, but it does not seem to work for tri-copters.

     

    I went over the code for a bit and unfortunately I just don't have the time (im the lead developer for my company so am fairly busy)  to learn all there is to know about AC2.

     

    Anyway, my temporary solution until someone with more AC2 knowledges comes up with an official fix (or shows us the light to the proper solution) this is what I done...

     

    In ArduCopterMega.pde find this code starting around line 841 and change it to match this:

     

    #if FRAME_CONFIG == TRI_FRAME
            // servo Yaw
            g.rc_4.calc_pwm();
            //APM_RC.OutputCh(CH_7, g.rc_4.radio_out);
            APM_RC.OutputCh(CH_7, (   (-1 * (g.rc_4.radio_out - g.rc_4.radio_trim) ) + g.rc_4.radio_trim  ) );
    #endif

     

    Basically commenting out the APM_RC.OutputCh line and adding the modified APM_RC.OutputCh. This will accomplish the same thing as adding a servo reverser (thus reversing both the yaw command from the radio and from the APM).

     

    Be sure to remove any channel reversing you have set in the APM or on your radio.

     

    This seems to work well. Unfortunately i cant test until tomorrow when the sun comes out. 

     

    The only potential issue i see is the yaw movement of the servo seems very small. This is my first tri so maybe its just enough. We will see.

  • I have the exact same issue. I just got Jakub's tri frame and almost done setting it up with AC 2.0.39 and noticed the same thing. Both the servo and gyro commands are reversed.

     

    Changing the direction via manlink via the planner IMO is not correct way to fix as this only reverses channel 4 (which btw, doing so also means you must arm holding down and left VS right), it does not reverse the gyro commands as you described.

     

    What is the fix? I would rather not tear my tail apart and rebuild it in reverse to fix this (which would).

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