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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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.

Checking through the full parameter list I noticed on FRAME that my parameter was 1 for X configuration but the attached notes state that tricopters and helis should be zero.  So I changed the param to zero and checked again for yaw....still no correction. 

I also checked the compass offests and my x axis offset is probably too high at 253.  I will re calibrate and report back.

I don't know if you're having the same problem as me. But here is my problem and solution. I built a tri. The servo direction was proper as controlled by my transmitter. But arducopter's yaw correction was backward which would cause immediate rotation of increasing speed. My fix was to change RC7_REV from 1 (Normal) to -1 (Reverse). This fixed the arducopter's yaw correction but made the servo movement backward as I control it. I fixed that portion by reversing the rudder direction in my controller.

It took me a while to figure out there are two yaw control mechanisms at work. Controller input and ardupilot input. Both have to be working in the proper directions.

I am currently trying to tackle this problem. I believe my servo is reversed, when I throttle up it tips to the side a bit and yaws the copter round and around. I'll try all of your suggestions including the rudder reverse. hope something can help me. 

Yes, I'd like to confirm my success with reversing of the servo. I had a perfectly fine working tricopter with a Corona DS-238HV servo.  I then switched to a Hitec H-82MG. (Old servo was getting sloppy).  No changes had been made to the software or mechanical arrangement.  However, I found that both radio Yaw control and APM Yaw correction were now backwards.  (Rather, the new servo responds reversed to the same PWM as the old one).

I was able to fix this by changing RC7_REV from 1 (Normal) to -1 (Reverse).  This effectively reversed ALL PWM signals to the servo.  No changes were made to RC4_REV or in the radio.

I can confirm your solution is how I did my tricopter. 

Hey Harry, glad to hear you're going the tricopter route, its certainly a fun one. I'd say for you.. the most vital piece of advice I've discovered is that the tricopters tail, Yaw stick that pivots the copter around on its horizontal axis, NEEDS to be reverse of the input you give it from the transmitter. so I ought to look like this in mission planner, etc.

With RC-7REV @ 1 --- 

Transmitter >>> Left Yaw

APM Planner radio calibration page >>> Left Yaw

Tricopter Tail Movement >>> Tail tips to the right (This is due to the fact that the copter tail wants to tip it this direction, which pulls air to the right, causing a left turn - yaw)

and vise-versa for Right Yaw.

Obviously when you're spinning up your motors, its a bit scary seeing the controls be reversed esp not knowing thats the correct way, so its incredibly nerve racking to just say oh well and get on with it, but this step is important to get over the hump. Once you get it airborne, everything sorts itself out. What I do specifically in this case is when I spin up the motors to get going, if my tail is leaning to either side, I'll give small amounts of yaw stick, flicking back and forth, to get it to center (which it eventually does) and at that pt, I lift off. 

If your problems persist, let me know and I can send you my params for my tricopter that functions normally and or some more help.


This took me a couple days to figure out and google search much like yourself.  So I would just like to post the google search terms I was using to describe the problem.  This is a great community, thank you everyone that posted!

Ycopter yaw is erratic

Tcopter yaw is erratic

tricopter spins uncontrollably

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