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what can I do to make my gimbal more wind resistant?
  • Hi guys,

    I'm trying to tune my 3 axis gimbal but whatever I do I always gets more or less vibrations in wind. I'm not talking about huge gusts but 5+ m/s wind which can easily destroy my footage.

    I fly hexacopter with:
    - this gimbal http://quadframe.com/collections/frontpage/products/medium-size-bldc-gimbal-v2
    - this dampening system and legs http://quadframe.com/collections/frontpage/products/gimbal-dampening-system-v004
    - nex 5k camera (quite light for these motors so weight should not be an issue)

    Gimbal is perfectly balanced and works great in hand and on the ground but in flight it produces lots of shake in roll (can't see anything unusual in YAW or PITCH)

    Any thoughts?
  • Rotating landing gear is often a problem. There is plenty of area where wind can shake the gimbal.

    The smaller the mechanical construction is, the better it can take wind
  • yes, I know but can rotating landing gear (I guess we speak about yaw motion) affect the roll? If this is the case what would be the best idea to at least try to clean such relation up?
    From my observation yaw seems to be rock solid ad the only issue I can see is roll.

    I think filtering could help somehow but I have no idea on how to figure out the settings.

    Did anyone try that new FW versions with 'analyse" options? I'm wondering how precisely we can narrow problematic areas of our setups?

    If there is no suggestions, shall I get rid off that landing gear and use foldable legs instead?
  • The roll could be a separate issue. the Roll gage is quite big and the motor is not that big. More importantly, does roll move totally feely?

  • while moving by hand I cant feel any resistance. everything seems to be absolutely OK. What I have noticed though is that when I knocking the roll gage I can easily take it out of balance - much easier than in pitch or yaw case were I need to use a bit more force to take it out of steady position. This made me think that the motor is not strong enough.
    Later on today I will try to post some videos of my setup, BGC settings and then the video taken - maybe this will give you an idea.
    I was already thinking to get a bigger motor for roll but I don't really know what motor will be good and strong enough.
  • I replaced the flatpack freefly style Carbon fibre legs with 12mm carbon fibre round tube (much like the new 'freefly aero' legs. Much less surface area than the origional legs. seems to have helped a bit.
  • I manage to get quite a decent results. After rebuilding whole gimbal's mechanical setup from scratch and perfect balancing the stabilization performance is where it should be .. almost. All seems to be fine except one case ... there is a bit of ROLL shake time to time .... it's most visible when camera is pointing down. I'm now wondering ... is it possible that air coming from main air frame motors is interrupting roll performance? From the logical point of view it make perfect sense. The roll bar is placed perpendicularly to the air flow coming from props therefore it's much more prone to wind (air flow) distortion than any other axis. When the camera is looking down then roll surface is even bigger which makes it even more roll sensitive - is my way of thinking correct ?

    I currently fly 800 mm hexa frame with 14 inch props .. this gives me about 430 mm distance from prop to prop and I starts to think it's not enough. I'm thinking on arms extension to 900mm or even going to something like Tarot X6 where all arms are raised a bit causing by the same motors airflow goes a bit out side rather than directly down ... do you guys think this would help?
  • Look the http://levitezer.com/styled-2/blog-2/index.html posting.

    It is only GoPro, but the propellers partially overlap the gimbal/camera, I was pretty sure it will not work and equally surprised when it did work very and very well.

    I think it is two factors.

    1. Very small and compact gimbal, that always helps

    2. very fast and powerful, thanks to encoders.

    3. and maybe 3rd. very stiff vibration dampening. I was surprised also that the very simple pipe insulator vibration dampening worked perfectly.

    Though this works well, on bigger gimbals I would make sure that propeller downwash does not hit the gimbal, so I think your idea is good.

    Often also vibration dampening can affect.

    And maybe the gimbal is prone to vibrations when tilted down, so also PID tuning on the position it vibrates would be good.

    But the best advise I can give is to make the gimbal as compact as possible.

  • Thanks a lot Garug, as always valuable piece of information from you.
    The gimbal is quite compact I would say (some pictures already included above) but the second point took my whole attention. Have you tested encoders on your gimbals? Is it really worth to get them on the gimbal? I was googling for some info regarding this topic but haven't find much to be honest. If you have any valuable links which can be shared I will be more than grateful.
  • Encoders are simply just awesome. You can run the gimbal with much higher voltage than you normally could. That provides very fast speed, and a lot of power. With encoders you can run full power on GUI, though I usually keep it around 200 to allow voltage compensation.

    Encoders do not solve every problem, but they make a good gimbal even better. This is with the latest LeViteZer encoder gimbal
    It is specially designed for BMMCC, just the camera is missing.


    Ps. does your gimbal have landing gears under the vibration dampers like on this picture http://cdn.shopify.com/s/files/1/0086/7002/products/DAMP-004_03_23cee41f-e582-4af4-b4eb-7be05af33d4d_1024x1024.jpg?v=1407401475 ?
    That would not be a very good idea. Plenty of area where turbulence could hit and shake the hole gimbal. Much better to attach the landing gear to multicopter.
  • Yes this is exactly the setup I have. I guess you might be right about the landing gear attached to vibration dampers. Need to test it somehow. Maybe I will attach small mobile with accelerometer to the gimbal and try to log shaking move while flying - not sure whether this will show anything but at least it's a good point to start with.

    Coming back to encoders. So from what I have understand I need to get a gimbal with encoders already build in ... there is not really possible to get third party encoders and put them on the frame above - am I correct?

    I will look around and maybe some usable solutions are out there ;)
  • ok ... initial investigation done ;) ... I think I will go with AS5048A. I could attach magnets directly to the motors and then print some 3D holders for sensor which could be attached to the gimbal arms ... I have never tried encoders but form what I can see it's more than worth to give it a try.
  • Small cameras and gimbals are prone to vibrations and rolling shutter (jello effect), so they are a bit more demanding in terms of balance, stiffness, smoth and proper operation and fine-tuned settings than those bigger, heavier setups with GH4 or Red cameras...
    Maybe the encoders would help you, I'm curious. Tell us how it goes!
  • After typing in this forum, I guess using basecam controller.
    In the analysis tool can analyze gimbal. If you carefully read the description and after a test come to the conclusion that announces gimal be a stiffer suspension. The more compact Gimbal - so the smaller the acceleration of vibration.
    test with harder damper. We can put Bluetooth and set during the flight
  • unfortunately putting encoders on my gimbal will not be that easy as I initially thought. Yaw will cause a problem because of complicated mechanical build. I will need couple of days to figure this out.
  • Best thing would be to try without landing gear, it might slow the problem, and try also stiffer vibration dampening.
  • I have already stiffer vibration dampening and it seems to be better already. Previously when I was panning the camera up or down almost every time I released a joystick command, the camera was getting a bit of jerk while trying to slow down. Now when the whole dampening system is a bit more stiff this strange jerk does not appear anymore. It seems that while fast slowing down (usually it appears in dynamic movement) the camera weight was influencing a dampening which later on can cause a bigger error on a IMUs. One thing bothers me a bit though. I can understand that camera IMU can be giving bigger error (more movement) thanks to lose vibration dampening system, BUT there is also another IMU placed directly on the gimbal frame (under YAW) which is also getting same movement information (shake caused by vibration dampening). Having data from both sensors, shouldn't this be somehow calculated to provide better stability?

    So far the stability seems to be better now but I need to take it in to the ear to test it in real condition. Unfortunately it's raining since couple of days and I need to get a good weather window.

    Interesting thing. Yesterday - just for test - I have replaced NEX 5(about 300 grams) with Nikon D3000 (about 700 grams) on my gimbal. After balancing it appeared that gimbal is working absolutely perfect without touching any of PID tuning or any other value. I was pretty surprised ;)
  • A force needs a counter force. Gimbal rotating camera causes momentum, soft vibration dampers do not resist it a lot. That can cause vibrations.

    On post #3 you can find my approach to the vibration dampening http://www.rcgroups.com/forums/showthread.php?t=2254102
  • one question. How important is precision of 6 point IMU calibration? Today I was trying 2.5 GUI and firmware (previous 2.43 version was working fine for me). I went through 6 point temperature calibration and I have to say the results are much worst. Actually I can't get decent stabilization and I can't even say why. The only thing I can think of is 6 point IMU calibration which I did very fast and probably not accurate enough. Both sensors were packed in EPP foam to assure slowest possible temperature changes. I guess sensor might move inside the foam while calibration process.
  • You can destroy the calibration if the IMU is separated from the gimbal and when installing it back. any pending of the IMU when screwing it will change calibration. I use mostly two sided tape or nylon screws.

    The Temperature calibration works great when everything is perfectly performed, but that is difficult. I do not usually temperature calibrate, but just normal 6 point calibration when IMU is installed on its place and performing gyro calibration when operating in different temperature. Just allow enough time the IMU and gimbal to settle with the ambient temperature before performing gyro calibration.
  • I don't really understand why screwing the IMU back could destroy the calibration?
    Anyway it shouldn't be an issue in my case. I use two sided tape for frame IMU and same for camera IMU. Actually the camera IMU is attached to a plate which is then screwed to the bottom of the camera plate.
  • hmmm ... one thought just came to my mind .. I have used magnetic screwdriver to install the camera IMU plate back to gimbal. Could that destroy the calibration?
  • Magnets should not affect much, at least when they are only temporally. The IMU is electro mechanical. Pending circuitboard can pend the chip and that affects the calibration. As you describe it installed, it should not pend.
  • Well after multiple attempts on 2.50 GUI and 2.5 firmware I couldn't get stable behavior. When the gimbal was leveled everything seemed to be fine but when I tried to move it around to test pitch it turned out the gimbal (pitch to be more specific) went absolutely crazy. I looked like the gimbal was way to slow to compensate changes of movement direction. After I increased D a bit more it helped but then high frequency oscillation began. I tried multiple combinations with pretty same result all the time. Similar with RC given commands. Panning camera down or up was causing the issues. I will try to make a video to show behaviors on both firmware versions.

    I gave up with 2.50 and went back to 2.43b9. After firmware upgrade I loaded my previously saved profile for same camera. It works much better than 2.5 and I have still not performed acc calibration.

    Any idea why 2.5 behave like this ?

    And this is not the issue with PID tuning. I think it's safe to say that 2.5 is not working at all for me.
  • More likely it is some setting that was not ok on 2.50. With some older FW I had some problems with IMU calibration after updating, Erase EEPROM solved those problems. Now I am at 2.56.

    Note: you must use GUI that corresponds to the FW.
  • hmmm .. that might be it. Tomorrow I will try again with latest beta version but this time I will Erase EEPROM first.
    BTW what is your impression with 2.56. Release note is saying something about core mathematics change. Is it really that good? Is it worth to try?
  • it is good.
  • Hello Garug,

    Ok .. I have erased the EEPROM and installed 2.55 GUI then upgraded the firmware to 2.56 ... after both IMUs calibration I tried to auto tune PID values but again I have failed. The video below shows how the gimbal behaves.

    https://youtu.be/YFwCrOHrPTs

    I have seen pretty much same behavior on 2.50 GUI and firmware. On above video I'm trying to pan via RC controller. Actually after couple of secs you can RC controller stick movement and then corresponding gimbal behavior. Also when I'm knocking the pitch, gimbal goes crazy.
    I'm running out of ideas. I think I will go back to 2.43. On that version I know what to expect at least while 2.5x does not behave as I would expect.

  • There is something seriously wrong. It looks front heavy, but even if so it should not cause that. I the pitch well balanced?

    Did you say it works ok with older FW?

    There is the euler angle orders on new FW, but should be ok if you have not changed it and it should not cause that.

    It looks like something wrong with RC. If you disable all RC from GUI, how does it work then?

    Are all axis moving freely when unpowered?

  • Thanks a lot Garug. As always light speed reply from you - appreciate.

    Actually you made me think on free movement while powered. It turned out pitch was a bit tight. I fixed it and double checked balance and it's perfect now. Went again through PID auto tuning then again manually and still same thing. Pitch is getting crazy as you can see on the video above.

    Answering your questions:
    Yes all axes are well balanced and move absolutely smooth and easy - just double checked
    Yes it works almost perfect on 2.43b9
    With RC disable same behavior while knocking the camera. When I'm moving whole airframe causing pitch movement the camera goes crazy as well - same thing.

    Actually same thing was happening on 2.50 firmware. That was the reason I moved back to 2.43 in the past. Thing is that this software improves over the time and I really would like to try it.
  • The 2.50 is better than 2.43, it is something else. I had long time ago some serious issues you have, but that was after testing many beta FW. The solution was to load EEPROM from other card. But if yours is working with 2.43, strange. You could try the news beta, just enable checking Beta.

    Are you always using the corresponding GUI (same number as the FW)?

  • Actually I'm now running 2.55 GUI and 2.56 FW - I guess it should be OK.
    Tomorrow I will again try to run 2.43 to see whether it's still fine.
    Will keep you posted
  • One thing the picture above remind me that this is RLG. On the video it is standing on landing gear? have you Yaw disabled? If you have yaw activated, the hole thing must hang from the yaw so that it can rotate. Otherwise anything can happened. If 2.43 work better on that situation, it could be, but it is not meant to work like that. If yaw is activated, it must be able to rotate.
  • No no. Whole set (airframe and the gimbal) are placed on a special holder to allow free Yaw movement. Actually on the video above Yaw was completely disabled. Strange thing is that only Pitch seems to behave like this. Although I have newer got to the point where Roll and Yaw were perfectly tuned (FW 2.5x), both these axes seems to be quite fine if I compare it to Pitch.
  • The strange thing is if it works with 2.43.

    Otherwise I would suspect HW failure, especially would check Pitch motor.

    All axis should work just perfectly, 2.43 or 2.50, the basic stabilisation works just great on both FW.

    It could be that something is corrupted on EEPROM. But at this point I would say likely it is something else.

    After you erased the EEPROM, did you do the complete basic setup again? I would advice to do so, make sure motor inverted is correct, set motor poles manually, make sure of IMU alignment and GUI configuration and calibration etc. It could be something like this causing the problems, but strange thing is if it works with 2.43.

    It could be also that PID tuning is very wrong, did you auto tune it with good stability settings? Autotune the pitch axis only with good stability setting. You must tune PID when changing FW. PID scaling has changed on some FW versions.
  • OK .. With your help Garug I finally figured this out, although the root cause was so silly, it's even shame to talk about it. Anyway, it turned out that my both axes Pitch and Roll had wrong INVERT setup.
    Every time I moved to 2.5x versions I took a short cut and simply loaded my best working profile from 2.43 FW. It seems that three things could actually happen:

    1 - either profiles are not keeping info about motor configuration
    2 - either the logic changes between various FW versions and same motor configuration does not fit all of them
    3 - somehow I might corrupt the setup in my saved profile and simply loaded wrong data to GUI and then to the board (seems to be most realistic option to me :/ )

    Right now gimbal seems to work quite good on the table and in hands. Today will make couple of tests with props on and finally try to fly this baby once the weather allows.

    One more question. Some time ago You have advised me to move second IMU under the YAW and it was just a perfect move. Right now I can see new option in IMU configuration panel - "Below Yaw + PID source". I guess it's better to use this option rather than standard "Below Yaw", unless you have different point of view.
  • The wrong inverted has happened for me too, and not so long time ago :)

    I would recommend starting with normal Below Yaw, the +PID is more experimental, but it could help RLG, so it is worth of try after you have first tested normal Below Yaw.
  • So today I finally got an opportunity to test in flight. I have to say I'm very impressed with 2.56 FW performance. Although auto PID tuning seems not to work almost at all, after 10 - 15 min of manual work I was done with basic tuning. My first observation - after basic tuning of all axes gimbal seems to work stable in all positions. On previous FWs I always had to use filters to fix camera look 45 degree down position (pitch), which always was problematic (high frequency osculations) for me. Right now I don't need to use filters anymore (at least for now ;) )
    So I took it in the air and the stabilization is noticeable better than before. Still some small vibrations appears from time to time on the roll but I think it's far better than it was before. I also manage to read real data from monitoring tab on the fly and need to say that there is lots of vibrations coming from the airframe. I guess it comes from props. Although all are already balanced I really doubt in my balancer precision. I have already purchased another one and as soon it arrives I will double check everything. If it comes to dampening system I thing original one works quite well. Couple of days ago I made it a bit stiffer by putting small pieces of foam between dampening system plates. Today I have tested the gimbal with and without them and it seems without is a bit better ( I could observe less roll vibrations).