APM 2.5,Firmware Version 2.8.1 - Yaw trim? - Discussions

Disclaimer: I'm not sure where the best place to get help, so I've also entered the same question at: http://www.rcgroups.com/forums/showthread.php?t=1776457 and http://diydrones.com/group/arducopterusergroup/forum/topics/apm-2-5-firmware-version-2-8-1-yaw-trim, sorry for the duplicates

Hello, I recently upgraded the firmware of my APM 2.5 to 2.8.1 and on the very first flight post-upgrade I noticed that the heading of the copter rotates counter-clockwise. I have to compensate with the yaw stick in a very significant manner to stop it from spinning. The other axes (roll, pitch) have no issue.

I order to fly comfortably during the last flight, I trimmed the yaw on the transmitter to stabilize the yaw and was actually able to fly well like that, but from what I've been reading, it is not recommended to trim the transmitter on multi-rotor aircrafts, and much less on the yaw axis.

I'm not sure if it this is an issue with this release of ArduCopter (2.8.1) or hardware issue with my aircraft. Note that this issue didn't exist on my copter with the previous fw version 2.7.2.

Here is a graph of the yaw behavior. Notice that the Yaw IN (green) line at the bottom left of the graph is high as I arm the APM. Then around "Line" (x-axis) 520, when I actually take off, the YAW immediately starts falling, although my yaw input (YAW IN) is at zero.

Has anyone else had a similar experience with their tricopter/multi-rotor helicopter and the Ardupilot-Mega platform? Could it be that my servo angle is not correct for the middle stick position?

Any insight would greatly be appreciated.

Thanks!

Hardware details:
Multirotor type: Tricopter
FPVManuals Frame, with wood booms.
APM 2.5
Hobbyking 2830 1100kV outrunner motors (discontinued)
10x4.7 props
Turnigy TGe 9g Micro Servo on the tail rotor

Did you ever find out more about this initial yaw problem?

I'm bench testing my new APM 2.6 with 3.1 firmware.

When I do a runup of the motors, diagonally opposite motors are definitely getting smaller pwm's (e.g. 1700 vrs 1900). This would lead to yaw on takeoff I'm sure.

It's as if there is a lot of yaw trim being applied prior to takeoff.

As I'm sure you know, this has nothing to do with ESC calibration.

From what I'm seeing in the forums, and what you said in your posts, the problem straightens itself out quickly in flight, but still, I would like to see a bench motor runup produce essentially equal pwms to the ESC's.

Any comments or other help would be appreciated.

C. J. Klingman

Replies

C J Klingman November 12, 2013 at 1:07pm

Did you ever find out more about this initial yaw problem?

I'm bench testing my new APM 2.6 with 3.1 firmware.

When I do a runup of the motors, diagonally opposite motors are definitely getting smaller pwm's (e.g. 1700 vrs 1900). This would lead to yaw on takeoff I'm sure.

It's as if there is a lot of yaw trim being applied prior to takeoff.

As I'm sure you know, this has nothing to do with ESC calibration.

From what I'm seeing in the forums, and what you said in your posts, the problem straightens itself out quickly in flight, but still, I would like to see a bench motor runup produce essentially equal pwms to the ESC's.

Any comments or other help would be appreciated.

C. J. Klingman

This reply was deleted.