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Alexmos 32bit doing strange things - bad PID settings
  • Hello could you look at video below - PID settings in vid's description - can you please guide me what possibly be wrong ?
    setup - GH4 with metabones adapter + Nikon 35mm f/1.8 DX. Thanks a lot
    https://youtu.be/zcumYiDgovk

    i need to shoot with it on weekend :/
  • So what do you think is the problem? It looks totally fine for to be operated in normal position. Handle rolled 90 degrees wil not ever work, nothing to do with PID. When it is rolled like that there is no motor taking care of yaw.

    Handle tilted back 90 degrees is ok working position, but your gimbal has some flex (every gimbal has) and the PID settings are too high to work on that position. If you need that position, tune the gimbal on that position.

    You could also try filters and activating adaptive PID tuning.

    What gimbal i that? it has really strange motor configuration, very smal Pitch motor, huge Yaw motor and double that for Roll. Normally it is the Yaw motor needing most power and support.

  • thank you for answer. here are my settings of PIDs
    ROLL // P 14 // I 0.3 // D19 // POWER 144
    PITCH // P 7 // I 0.23 // D 6 // POWER 100
    YAW // P 21 // I 0.24 // D 24 // POWER 164 +65

    doubled motor on roll axis - one for roll and one for pitch - power transfered with belt. its some czech indie made gimbal - my problem is that with some heavier lens even Handle rolled to 90° worked fine - so for handle tilted position there is to much PID ? i was thinking too low before :)
    problem is there are some light vibrations when its Handle rolled before 90°
  • A bit complicated, but cool idea. I think it is the belt or lens is causing the noise. maybe it flex or is too loose, is it possible to adjust it? Identify the source of the noise, that is what you need to fix.

    Your Pitch settings are clearly already low, so it would be good to see what can be done mechanically to improve the Pitch. You could try to lower 'I' for Pitch, but look the mechanics first and also, do you need to use the camera on handle tilted 90 degrees back? if not, do not worry about it, just set the gimbal working well on the handle positions it will be used.

    It could be that when the handle is tilted back, the weight shifts so that belt loosens up, or maybe it is the lens.

    Different lenses behave much differently, it is not only the weight, but how solid they are. Big loose IS unit inside the lens is bad. also some lenses like Canon 50 1.4 have much free play and are very difficult. also if the lens attachment to the body is not solid causes problems.

    Remove anything that can be removed and feels loose, make sure that filters etc. are well installed, loose filters cause problems.

    Try also lower power for the Pitch, PID for Pitch need to be retuned after this.
  • yes its cool idea and working good so far :) there is no any tight/loose option for belt - see pictures http://flyrecord.cz/012_Gmb_Enki_dslr.html Pitch settings is that low because if i even higher D for 1 or 2 vibrations comes up even in steady position so D 6 - 7 for pitch is maximum for me .. i must even lower power of pitch motor from 146 to 100 to reduce vibration on that settings. Mechanically its balanced perfectly. There are some light vibrations at ~40°-45° when Handle rolled and its ruin my shoot - only at 90° are so loud that you can hear them :)
  • See the updates regarding lens above. I would try to lower the Power even more and retuning the PID, should result higher PID with lower Power.

    Also see the filters, http://www.levitezer.com/styled-2/blog-2/files/archive-oct-2014.html

    Ps. I am a bit surprised if there is no adjustability for the belt, maybe you could ask from the manufacturer.
  • i see, Nikon lens has no IS and its quite solid i think ...
    ok i can lower power to minimum 80 - thats min for that motors (approx. 40% of power) and even with that i cant setup PID for pitch more than 1 - 2 stops - looks same with 100 power .. but problem is i am not 100% familiar with PID setting up and i will look at filtres but its even more complicated :) manufacturer set my gimbal to GH4 + samyang 14mm (heavier) but there is a problem that camera body is too light and it must be positioned too near from gimbal body caused limited rotation so I bought lighter lens and bypass this issue .. but this new one came up :/
  • There is really bad noise at 0:20 on the video, where does it come from?

    It looks like maybe the camera installation is not really solid. With very light lenses I use only camera body installation, with bigger lenses I use camera+ speedbooster installation and in addition flash shoe. It really makes a big difference how well the camera is installed.

    Remove the cap (if on place) and hood from the lens, does it affect?
  • no no, noises at 0:20 came from gimbal vibrations - really :) same noises makes gimbal without whole camera - in this case noises are louder because of "rings for strap" on camera body vibrating too - you can see it in video.

    no cap here and hood stay solid - but same without it
  • "rings for strap" , I have removed those. Clearly something is shaking badly at that position.

    I think you should ask the manufacturer if/how the belt can be adjusted. I think there must be some way.

    And it would be good to look in to the filtering, it can really help.

    First if yo have not done so already, try auto tuning, holding the gimbal in hand and on position it vibrates worst (on the handle positions you will be using the gimbal). Tune one axis at time. set the stability slider first 1/4 up from good stability. Make sure adaptive tuning is not activated when doing this.
  • How many poles are those motors? is the belt drive 1:1 ration? Have you correct pole numbers on GUI.? have you set the inverted status with Auto?
  • I already tried AUTO PID tune - always from zero at all axes .. i will try with your recommendation, thank you.

    in this position vibration is more visible when i use higher D on pitch axe (no visible moving or shaking on belt) must be one of motor and vibration just relay through whole gimbal

    these are 42 pole motors, belt drive looks like 1:1 ration, inverted status setted up but i just lower power pro Pitch motor (at manufacturer recommendation), no more changes made on motor setting by me ... i am new in gimbal world
  • And you have a very special gimbal, so it is new for both of us ;-)
  • anyway, thanks a lot for your time and advices i wil try your things later today and if there is no change so far i must go to manufacturer to set it up (its very long way) because i need it this weekend