I´m with APM now for a long time using it on a X-Frame. Working perfect.
But now I built a custom Frame for use with a GoPro3. It´s like a “Spiderframe” but distances of all motors to CG are the same. I tried using the X-Frame in the setup, but the results are not the same as on a X-Frame.
Due to the higher weight outside the center (cam in the front, battery in the back) I believe its more complicated to handle the settings.
Copter is flying nearly ok, but have some problems with yaw (banks up to 5° in 45° axis to forward/backward)
It´s overshooting all the time and wobbly when a yaw command is given.
Think thats because of the high masses outside the CG, right?
But I changed the Frametyp to V-Frame (althougt it´s not a V, because of same distances of Motors to the CG). Nothing changed. Same wobbly behavior and overshooting when yawing.
Would it help if I set Frametyp to “H-Frame”?
What can I do to get more stability on that typ of Frame?
Can someone explain the differences between X, V and H Frame for the settings?
I played for hours with the PID´s, but can´t get a satisfying result.
Center of Gravity = center of lift
Motors all same distance to CG/CL
Takeofweight is 1850g.
Hover at 50% throttle.
External MAG using and calibrated (2% after Compassmot)
Can somebody give a hint what I have to change? Frametype? PID´s?
Attached a Photo to see what kind of Frame I´m using.
using APM2.5 with newest 3.1beta (but same with older Versions like 3.01)
have no flightlog, but can do a log (which settings for log? Default?)
Vibrations on X,Y between +1,5 and -1,5
Vibration on Z beteen +8,5 and -11
Motors: TigerMotors MN3110 with 11" Carbon Props
APM 2.5 is placed at CG/CL
Distance to Motors =30cm
Stable Hover and Loiter. At Full Throttle Copter is going up straight, not to any side.
Only Yawing is wobbly and at start of yaw Copter is tilting in 45° axis. left or right Motor is going down little bit and APM trying to compensate resulting in wobbling.
Lowered RateRoll P to 0.11, RatePitch P is 0.14
Stab P is 4,5 on both axis, but played a lot with differnt settings.
It´s more a general question, I think.
Just need a hint if this can be changed with PID settings or if it is impossible for the controller because of the high masses outside the CG to compensate this behavior.
As far as I can tell from the picture, if the APM is mounted in the CG, then your CG is not in the center of lift. You should double check and weigh out the actual position of the CG.
In a square geometry, the CL is exactly in the crossing of 2 lines drawn diagonally from motor to motor. Also weigh out the vertical CG position. Below the rotor plane is a bit more stable.
X configuration = square geometry
V configuration = Trapezoid geometry
H configuration = rectangle with long distance front to back and short distance left to right
The picture is bad and not from straight above, so it seems as you said.
But CG is exactly CL. APM is exactly under the crossing of the two diagonal lines from motor to motor.
Vertical CG and APM is on the rotor plane. That was my target when I designed the Frame.
So, for me it seems that the only reason is the mass of battery and Cam far away from the CG/CL.
Maybe someone can tell me the physical basics about this. I would understand that because of the mass and distance the copter is yawing slowly and overshooting due to the moving mass. And I would understand that roll is much faster than pitch. For that reason I lowered rate_roll P and raised rate_pitch P to overcome that.
There is more power needed to pitch the copter than to roll the copter.
But why is he behaving strange with yaw input?
Only for my understanding:
Is it right to lower the rate roll and raise rate pitch?
I tried to raise stab_p_ yaw to 7, but that made no difference.
And it made no difference if stab p on roll/pitch is at 4,5 or 6.
I played with all parameters, but copter is behaving same.
When there is a yaw input he is dropping to left or right forward, and that I don´t understand.
I triple checked CG and CL. They are exactly in the middle of the APM.
Any idea what to change in the PID´s to push me in the right direction?
Does it make sense to configure copter as a “H”-Frame?
For that I have to disassamble the copter because on “H” the motors spin opposite to the X-Frame (for a reason I don´t understand too).
Maybe someone can help before I do it and it doesn´t make sense.