basic help to tuning
  • Hey everyone,
    I just finished building my 3 axis brushless gimbal for my pocket cinema camera based on the nex 5 gimbals out there. I think I managed to balance the thing pretty well after watching the freefly videos on balancing. but now when it comes to tuning, I can't seem to get it working very well. I'll try to make some videos of the behavior I get, maybe that helps.
    But for now, are there any good video tutorials or written documents that help tuning a smaller gimbal like the one I got?
    I think I have the basic understanding how the PID values work, but no matter what I try, I either have one of the following problems: micro jitters on all axes, when I push the yaw or tilt axis it sometimes just doesn't go back all the way. Especially when it's just a weak push. Bigger pushes usually work fine.
    And when I'm in follow mode the gimbal goes completely nuts as soon as I tilt it too far up or down. It looks to me like the yaw motor can't handle the weight.

    Is there an easy way to find out if my motors are not strong enough? Maybe that is the problem?

    Any help will be appreciated!

  • I would be interested too as I'm in the same boat with similar equipment.
  • So is your Yaw really balanced? That is, if you tilt the outer farm of the gimbal 90 degrees, does your yaw axis stay in any position you put it. (and the same for Pitch and Roll.)

    Are all your axis moving freely?

    Is your gimbal solid enough and motors powerful enough for the camera.

    Is your IMU well positioned and calibrated?

    It is worthless trying to set the PID values before the above mentioned are ok.

    Each firmware seems to have different PID settings and also how they affect. Best thing really is just dry them. Set power to 100, and PID 10, 0.1 , 10 (FW 2.4). It probably should work somehow with these settings and then try to increase the PID values one by one and change the power settings if needed and see how they affect; the angular deviation when the gimbal is moved, vibrations when the gimbal is in use, so not only levelled.

    Try follow mode after all above mentioned is ok. For follow mode you may want to fine-tune the PID settings a bit differently than for the normal mode, but good normal mode settings will work quite good.
  • Thanks for the answer Garug.
    I think my gimbal is pretty well balanced. Here's a video of me showing that.

    Please let me know if it doesn't look like it's properly balanced.
    In the video you can also see where the IMU is positioned.
    How do I know it's properly calibrated? I did the whole 6 sides thing with the IMU taped to a cube.

    I spent some more time the other day trying to figure out different values. And I think I found values that somewhat work. It only gets critical if I turn the frame to extreme conditions. Then usually the pitch axis starts to freak out and causes micro jitters.
    I'll try to upload a video of the issue. Maybe that helps.

    But the big problem is still in follow mode. Every time I try to point the camera up or down more than 35degrees, the yaw axis caves in and the gimbal turns to the side slowly.
    To me it looks like the motor has not enough power.
    Is there an easy way to figure out the maximum weight a motor can hold?
  • Hi, it seems to be well balanced, a bit too well even, is there lot of friction on the Yaw motor?

    The motors look big enough, but I think your problem or at least part of it is the frame. It does not look like very solid for that big camera, looks like it flex and this flex makes it prone to vibrations.

    Other thing could be that your IMU cable is going long ways near the motor wires, and the IMU cable is long. Do you get I2C errors? Also the IMU position affects. I would put the IMU on top of the camera and shorten the IMU cable and let it hang loose for most of the way on the other side than the motor. But if you have no I2C errors this might not be necessary.

    Put it can be the PID parameters or too much power. I would put the gimbal near the position where the vibrations start and see how the parameters affect that.

    I had also a problem with yaw when tilting up until I figured out that using joystick caused this. If you have joystick, try going to normal mode and setting the gimbal level and straight and then entering Follow mode and not using joystick for anything other than tilt (Pitch). Also set the min and max.angles under RC setup to max values and do auto offset adjustment under follow mode tab if you have not yet done so.

    I hope this helps.
  • I think the yaw motor had a bit too much friction based on the quadcopter mount hanging 90 degrees. it's not really meant to be held like that. I'm working on building a handle bar to use the gimbal in handheld mode, that should eliminate any extra friction.

    I don't think the frame flexes much. I's very sturdy, made out of 100% metal. It should be able to hold the weight of the camera just fine.

    But I'll try to mount the IMU on a different position and do some more tests. I'm not getting any I2C errors though. The only time that I got them was when the battery was running low on voltage.

    I'm not using a joystick or rc controller yet. So that can't be the problem.
  • The friction is bad, it should not be there even if the camera is tilted, as it will be there when you tilt the frame during use.

    The frame looks nice, but it is not just question of holding the weight, but flexing couple of millimetres under loads, that causes vibrations. Normally for that size of camera it would be good to have gimbal that supports the Pitch axis from both sides of the camera. But maybe it is possible to make this frame work ok with that camera.

    Still about what is enough powerful motor: You can always add the power from the GUI power settings or by adding voltage (using 4S battery), if the motor gets hot with the settings needed for your camera/gimbal, then it is underpowered.

    There is one other problem I had with Yaw axis causing similar symptoms as you have. My Yaw motor had lost one phase, i.e. the motor internal wire was broken. with many gimbal motors this happens easily if there is any pull on the wires. You could verify tho by measuring the resistance between each 3 phases. Each phase should have about same resistance, likely in between 10 to 15 ohms depending of the motor (maybe you can find the motor specs.)
  • ok, thanks for the tip with measuring the motor resistance. I'll give that a try. I have a 3S battery attached right now and the yaw motor gets warm to the touch if I pump up the power to around 220.
    Warm to the touch should be ok, right? Or is this something I want to avoid as well?
  • Warm to touch should be ok. Above 80 degrees celsius the motor will be destroyed for sure. The magnets can not take that.
  • Still looking your gimbal, would it be possible to rotate the Pitch motor to out side the frame?

    This would make the gimbal much more compact and especially the links shorter and so less prone to flex and vibrations. Also try to make all the links as short as possible (but of-course it needs to be balanced)

    BTW how do you like the BMPCC? I have been thinking getting one too, I just hope there would be a booster for Canon lenses, maybe I wait for the next version...
  • hm, not sure if that works with the pitch motor outside the frame. but I'll have a look on the weekend. would certainly help with the balancing and might fix the problem that the bmpcc actually hits the top frame when rotated too far. you can see that in the video when I test the yaw axis.
    but it might then hit the frame with the motor, the other way around....

    I love the bmpcc. great little camera. a bit tricky to get good looking footage when you're coming from a dslr and are used to light meters and awesome white balance settings, but when you get the hang of it, that little thing shoots some amazing footage.
    As far as I know metabones is working on an EF to m4/3 speed booster that's supposed to come out this year with an active EF mount to change aperture and support for IS in lenses.
    I'm waiting for that to come out, in the mean while I'm using all my m4/3 glass I already own from my Olympus camera.
  • "bmpcc actually hits the top frame" I would not worry too much about that, it is actually good and prevents the gimbal cutting the wires when it looses control. Normally +/- 40 degrees movement should be well enough for most applications for Roll. Moving the motor outside would actually limit the Pitch movement down, unless the camera is attached from above. Anyway would be good to make the links as short as possible. Some soft material can always be added where the camera would hit the frame.

    I am really waiting for the Canon speed booster, good to know there is some activities on that.
  • @powerjosl I'm struggling with almost identical frame to yours at the moment. Mine is all aluminium and I suspect it is not sturdy enough for the weight of my GH1 with a heavier lens (together around 800 grams). What motors do you have? Also I went for older firmware (2.3) recently and the system is much easier to get tweaked. with 2.4 I wasn't able to get any usable footage. All seemed ok on graphs but once on the move I got lots of little jitters.
  • powerjosl: I have the same Gimbal (DYS 3 Axis). Here is a start point for all it is worth. Flying in wind today it wouldn't hold. I am still unsure how high to adjust the motor power, increase it till ???? It gets hot after 5 minutes? I've mounted a Canon ESO M with a 22mm lens. With the roll balanced my tilt is a bit top heavy, perhaps the difference with the Nex-5. I'm thinking washers to balance it.
    Also: You might want to balance with the lens cap off, made a difference for me.

    How did your PID's turn out? 3S battery BTW
  • @powerjosl I was looking this your video and the one below. I think you might have the problem with the motor axel they mention, based on how much friction there seems to be on your gimbal.

  • powerjosl It sounds that you´ll have to raise the power on roll axis. The D now has to be set much higher...around 30 and above...
  • I have the rc timer one and what i found is that the arm that holds pitch motor is not made precisly enough. On the joint (with thumb screw) there is some play and it is easy to have pitch and roll axis not intersecting in the COG. I had to adjust the gimbal on that joint, basically raising pitch motor a bit to align both axis. This allowed me to balance the gimbal much better for both axis.
    At the moment I have GH1 with a heavy glass lens mounted on it (900 grams) and I have he best results with low power on the motors (5010). Around 70-80. with lower power I can have higher P and D. Also I cannot get the gimbal to work with I greater than the minimum 0.01. Considering there is 3 of us with almost exactly same gimbal can we share our PIDs? What motors do you use?
    the best stabilisation for a handheld system I get with:

    GIMBAL Rc timer
    MOTORS 5010
    ROLL PID 18 0.01 32 power 70
    PITCH PID 10 0.01 8 power 70
    BATTERY 3s
    camera weight 900 grams
    firmawere 2.4

    at the beginning I tried tweaking it with much higher power settings (150, 180, 220) and it was good on the graphs when stationary but jittery on the move (resulting in rolling shatter issues). After a week of tweaking I tried much lower power settings and it is good. not sure how it will handle wind though.
  • thanks for all the reply guys. I haven't had the time to do any further testing, but I think the gimbal I have is not the same as the rctimer. I don't have the problem with the motor not fitting on the pitch axis.

    I received my bluetooth adapter today and the necessary parts to attach the gimbal to a handheld rig. I'll be doing some more tests tonight and try to incorporate all the recommendations people posted here.

    If I get it working I'll let you know ;)
  • @powerjosl my rctimer doesn't have the hole problem described in the video (they probably updated their design since). Yours on the video looks very similar if not identical. The principles of tuning will be the same for such similarly constructed gimbal.
  • Hey,
    Could you guys have a look at my post here,
    I guess it's a similar issue, but I need your advise,
  • @polas
    thanks for the info, but it seems your rctimer gimbal comes with different motors. the dys gimbal that I have came with 4108 motors.

    It tried to install my bluetooth module yesterday but couldn't get it to work. when attached, the gimbal doesn't work at all. the green led just blinks constantly and I can't even connect via usb. if I unplug the bluetooth dongle I can connect via usb again.

    anyone had success connecting the bluetooth dongle to the serial port?

    I think I also somehow fried my yaw axis motor. it now gives off some weird clonking noises when moving and generates tons of i2c errors. when I turn off the motor it feels like it has more resistance than all the other motors. I have to take the motor apart and see what's going on here.
    how would a defective motor behave that has been running too hot and got fried?
  • RX goes to TX and TX to RX, Bluetooth need to be paired, it had different default code than expected 0000 or 1234, works fine for me.

  • The jello at the end was caused by the Yaw arm hitting the plastic stops I put in to keep the legs
    out of the vidoe.
  • Thanks to this thread I learned that my YAW gain settings were too low and my power was too high. I finally got a flight where yaw didn't completely flip out causing the gimbal to go totally nuts. YAW has been killing me, but finally some progress!!!

    My Settings:
    Camera: 1080P / 60FPS / Shutter Priority at 1/125

    DJI Naza V1
    DJI F550 Airframe w/ stock motors/ESC's
    Graupner E-flite 10X5 props
    DYS 3-axis gimbal
    DYS-BGM4108-130T motors on all axises
    Sony NEX 5N Camera
    AlexMos 32-bit 3-axs Gimbal Controller (4S LiPO)
    Second IMU placed above yaw motor

    P | I | D | Power | + | Poles
    Roll: 25 | .2 | 15 | 100 | 0 | 18
    Pitch: 12 | .15 | 5 | 100 | 0 | 18
    Yaw: 8 | .02 | 12 | 100 | 0 |18
    Gyro Trust: 100
    Yaw speed (follow mode) = 6
    Yaw Offset (follow mode) = 55
    Firmware 2.40 b8

    Video Link: http://youtu.be/EWPHrfUUhRo
  • Is there anyone out there that is expert at dialing in a DYS 3 Axis for NEX5N using Alexmos 32 Bit controller? I'd like to send th eunit off to you and pay you to get the thing perfect as possible.

    Let me know.

  • Does anyone have the DYS 3 Axis working well with NEX5N ? I do not have the DYS 3, but looking the gimbal with NEX5N sized camera, maybe the problem is not the tuning.

    The motors should have excellent bearings for supporting NEX5N sized camera from one side only, and the metal parts look flexing. the 8 bit 2.3 was maybe easier for that kind of construction, later firmwares benefice of more solid gimbal. Just thinking.
  • Honestly, I am out of patience with this thing. I continue to miss shots due to gimbal issues. I don't believe it's the gimbal or controller but rather my inability to get he tuning down. i need to shoot, not constantly fiddle with it.

    What I can not understand is why there aren't simply standard PID's for this rig. It's bologna that "every rig is different so thats just not possible". Same camera, same lens, same controller, same gimbal. For the most part we are all trying to use the same rig for NEX5N AP/AV.

    As long as the flying platform is vibration minimized and balanced the gimbal should stabilize the camera well with some common PID's. But nooooo.

    Anyway, I'd just like to pay a guru out there to dial mine in for me.