I am working on troubleshooting and PID tunning a coax copter. Can someone explain to me that with it sitting on the ground armed in stabilize mode (motors not powered) that when I give it full right on the stick the flap extends all the way then after a moment it rotates back slightly. Almost feels like the servo overshoots its desired potion so it then rotates back. Happened with 2 different servos so I know it isn’t those.
Hello there!
“Armed in stabilize mode” and “motors not powered” seem conflicting to me. Are you running the machine with full battery power, everything configured etc., but with motor cables detached?
If you arm the machine, the flight controller will not directly translate your pitch/roll stick inputs into flap movements. Instead, you are commanding desired pitch and roll. The flight controller then compares these commands with the actual vehicle state and some limited flight history, and issues commands to the flap servos. Depending on how well the machine is standing, and how much of its own vibration it feels, it may do very different things with the servos.
One thing in particular is that the servo commands are inversely scaled with (commanded) motor thrust: to achieve the same action in pitch, the servo needs to move 2x less if there is 2x more thrust. This logic is not 100% like that, but if you push throttle really high - even with no motors actually running, it only matters that the higher outputs are sent - you should expect less servo outputs for the same situation. But “the same situation” is a complicated thing, and surely it’s not a 1-to-1 mapping like it is when the machine is disarmed.
(A shameless plug of my mostly coax copter channel: https://www.youtube.com/channel/UC-3IBECWHPQS8kWOrreJjsg/, you may learn something here)
Thanks for getting back to me. AS for the motors not powered everything is running off batteries but I have removed power from the escs so they do not spin. Have a dedicated BEC powering the servos.
I was looking at the raw data for pwm channel in and outs and at half throttle when I command fly forward. right joystick pwm 2004. the equivalent flap channel goes up to 2000, then falls back to 1800. So the autopilot is definitely controlling the outputs as expected I just don’t understand why it goes up to 2000 then back down to 1800 ish with the control signal value not changing
If you provide your logs (you obviously have them available based on this post), I may tell you what is happening in more detail.