Alexmos 8bit - different behavior 2.30 vs. 2.40, shaking YAW axis
  • Hello,

    I have a DYS 3 axis gimbal, it came with a legit mini Alexmos 8bit board, fw. is 2.30 b5. The stock PIDs were pretty good by deafult, I tweaked them a little more and the gimbal seemed to be in parameters (I have the expertise from another Alexmos based GoPro sized gimbal, so this wasn't the first one).
    My problem (and strangely, it happened the same thing with the other gimbal too) is that after updating the stock firmware to the latest 8bit fw (2.40b7) the YAW axis is going crazy. This is happening randomly (the other gimbal somehow, cured itself I guess:) ) as you could notice in the video I made:

    One may say: if 2.30 works why don't you stick with this version? The answer is that 2.40 has the "Estimate angles from motors" option under the "follow mode" tab and from my previous experience that option was the only thing that allowed me to incline the quadcopter at an angle of about 30 degrees without causing the gimbal to entering in a shaking state. I know the " Estimate angles..." option was created for handheld gimbals but in my case, I just could not use the 3rd axis of the gimbal without enabling this option. And my style of flight was not an acrobatic one at all :).
    OK, after watching my video, could anyone have an opinion about the possible cause? I tried numerous PID values, the gimbal is pretty well balanced and as I've told above, it happened the same thing with the other (mechanicly different but also Alexmos 8bit board) gimbal after updating the firmware. I must add that this issue occurs only when using the 3rd axis.
  • It is just too long video... where at it is the problem?
  • Hi Garug,

    Sorry for the long video, I just wanted to show the circumstances the issue is occurring.
    Jump straigt to 1:34.
  • It is still too long for me to have patience and I do not understand why you disable Yaw.

    Anyway it looks like basic setup or tuning problem. 2.3 is much different than 2.4. You need to retune the gimbal, and good also to ensure the basic setup.
  • OK, i'll try to re-tune from scratch, I've already did this but, never know, a new start could mean success.
  • I am back with good and bad news.
    Good news is that I managed to properly re-tune the DYS gimbal from scratch, I started as Alexmos manual says, low values PID and progressively increases them watching for oscillations. The result is pretty good, I am waiting for good weather for further testing.
    The bad news is that I tried to apply the same re-tune-from-scratch recipe to my other previous gimbal (let's name it "2D>3D" as it is a converted 2 to 3 axis gimbal ). I tried various PID values but the Yaw axis is disturbed by the Roll axis during the pitch tilting (the Roll tilting work OK) as I could see in the realtime tab in GUI.
    In the past, I solved this issue by enabling the "Estimate frame angles from motors" options, this time it doesn't work anymore. Unfortunately, happy with the DYS 3 axis success and being very confident that re-tuning will bring me success with 2D>3D gimbal too, I didn't save the initial settings.
    OK, here is a (short ;) ) video with "the good and the bad":

    I must add the fact that both gimbal systems have the FC stabilisation PWM signals outputs (ROLL and PITCH) fed into Alexmos boards. The flight controls boards are APM and NAZAv2