Trying to debug this Shake/wobble on the phantom

I just got finished replacing all the barrings in the motors to rule that out.

Still getting this wobble under load. It flies up okay, but this wobble is a deal killer as I can't get stable video this way.


I've balanced the props, so I'm pretty confident that's not the issue. Also, would that only be noticeable under load? In actuality it seems like the wobble goes away while I elevate.

The only change is if I switch to my CF props, but I have a hard time getting any elevation. ( I might fight with the gains some more with that one)

this has been a real head scratcher for me. I'd rather be spending time tuning my gimbal if you know what I mean

Oh and other folks with Phantoms are flying this gimbal with just a small sacrifice in agility , nothing like this wobble.



Skip to 40 seconds in to get a good example.

Jonas - How about programming the slider on the back of your transmitter to control the gain so that you can play with that while you're in the air. Maybe you can tune out the instability. It's really difficult to do it with the "tune and try, tune and try, tune and try" approach. It looks like it's over correcting just a little and causing oscillation.

...Tiger

I wish I could help. You either have a simple fix, or a nightmare.
My guess would be a harmonics problem, indicated by the shake,
Or vibration in the last of the video.
If it is related to RPMs, could be a prop out of specs, even though it is balanced. Maybe a motor out of balance, or a funky controller on one motor.
No idea how the props mount on your quad, but APV Electric props are
Cheap, if you need to experiment.
A change in prop pitch or diameter, might move the bad harmonics, to a less
Critical part of the power curve.

A free app on my i- phone, iseismometer, was a great tool, to solve a problem with my gimbal. Just move the phone around to different parts
Of the quad, and you can see where the vibration is coming from.
A couple rubber bands in the right place solved my problem.
I would have never found the problem without the app.
If nothing else, it might give you an idea where the problem is.
The app is free, so if it won’t work on your phone, borrow a buddies.

Please keep us posted and let us know about the fix.
No doubt, we will have the same problem down the road.
Make any changes, one at a time.
If you change four things at once,
And it solved the problem, you will never know which one worked.

Another thought,
Just un- power the gimbal, to see if gains or what ever, in the gimbal , are causing the vibration.
Did you have this problem , before installing the gimbal?

Yeah, my 1st test was to test the weight, so I taped 4 "c" batteries which worked out pretty close wight wise, to the bottom and had the same symptoms. So we can rule out the gimbal action I think.

One possibility I thought might be the legs (although kinda a pain to test) that since the compass is mounted on the legs, and they are a tad more springy with the added length, that that might be getting shaken by a vibration and then reinforcing the effect by confusing the quad into thinking its moving. Their definitely a requirement though since the gimbals hangs down pretty low, and my last ones buckled under the force of the crash.

In what way we're you using the rubber bands, I have a android vibration app so I take another pass looking for stuff.

I wonder why this is happening under load, but a) not when the weight is off and b) not if I use my CF props.

the CF props just give me no power oddly, which seem like it should be exactly the opposite. They are a bit banged up on the ends though but not so much that it shouldn't lift.

okay did some more testing tonight.

Its definitely something that builds up. I get sometimes a second of smoothness and then it creeps back in.

I tried adding some supports to the tall landing gear, it MAY have make some improvement but solving it.

I tried moving the compass off the leg, taped it up above the battery ,re calibrated the compass, but same harmonic wobble creeps back in.


The wobble continues with any left to right (and I think forward and back) motions. Only thing that seems to not do it is up or down.

My problem was not this complex. Flight was OK.
Bad video. Cheapest gimbal made, servo driven.
Part of the problem was flimsy materials, and maybe a bit of slack in the servo gears. I just ran rubber bands from the camera base to the legs, to pre load the backlash.
Solved the problem.

Maybe something loose?

The first suggestion, is probably dead on. If there is no problem with straight up, or straight down, that would rule out prop cavitations,
And so would the CF props. The flight controller doesn’t have to think, Just increase or reduce power.
To hold, or maneuver, now the flight controller is continually changing motor speeds. If the gains are too high,
Over control both ways. Probably so fast, it looks like vibration.
No idea about the compass, but if the flight controller, or sensors are loose,
It has no solid reference. It will try to correct for movement of the controller.
Hang in there! You will find it. Let us know --
Sorry, I probably know less about this than anyone -- Still baffled by simple problems.

Our washing machines does that sometimes. Maybe the clothes have bunched up on one side of the drum.

I agree with Tiger. But I don't know if you can program the slider on that DJI controller to control the gain. Here is a video where a guy has modded his DJI radio with a knob so he could adjust his gains in flight:

okay some progress. Turning the Pitch Roll gains and attitude gains seems to help a lot. Down to 75% on the attitude.

I hard motion to the left or right can trigger the effect though.

Just a thought... Have you tried physically removing the gimbal from the Phantom and seeing if it still shakes?

Yep, and without load is doesn't seem to do it, but if I put a equal load back on (tapped on 4 C batteries) shaking started again. So I don't think it's any sort of motion of the gimbals, but the weight of it seems to make the issue noticeable.

When you taped the equal load (C batteries) on were they firmly attached to the Phantom chassis, or were they attached via the rubber insulation dampeners?

Well as firmly as scotch tape allows.

Both the firmly attached dummy weight and the rubber isolated gimbal produced the same effect.


I made some further improvements by rigging up some supports to the tall landing gear.

He's my current theory, I've got something vibration happening that might even be some issue with a motor. And that vibrations is getting transferred to the fairly wiggly tall/wide landing gear, causing it to amplify the effect like a tuning fork or something, and 3 the quad is trying to right this wrong, and it was making it even worse.

Just keeps sounding more and more like a tuning issue to me.

...Tiger

Yeah I'll play with the gains some more. Unfortunately the P2 is ridiculously locked down. The naza is technically a "Phantom-naza" and I'm pretty sure I wasn't able to use the Naza Assistant software, only the P2 assistant software, so I don't THINK I can reassign the pitch control on the back to the gains.

I'll take a better look though because the try and tweak is pretty time consuming.

Worth a look!
Check the Important warning about Wi-Fi with the blade. Could be your problem. It is in Red letters on the right side ---
http://www.horizonhobby.com/products/350-qx-bnf-firmware-2-0-with-safe-trade-technology-BLH7880A

I think I saw a note on the subject on the DJI site also.
Looks like the 2.4 band is getting a bit over-loaded

Larry

This is just common sense! Why would anyone mount a 2.4GHz transmitter (GoPro WiFi) on their quad that's being controlled on 2.4GHz. Talk about a bad idea!

...Tiger

That's what I was thinking but then there is this:

DJI Lightbridge
http://www.dji.com/product/dji-lightbridge

It looks like this device replaces your radios control with DJI's and bundles it with the video downlink.

They claim "Anti-Interference Technology" but my guess is that they could make a 2.4 Ghz device and avoid having to make multiple frequencies for all the global markets they sell in.

I also wonder if their "Anti-Interference Technology" only applies to their own brand radios?

Yeah I'm confident it's not interference, but thanks. And my video is on 5.8 so we're good there.

I've got the wobbles under control my dropping the gains. So that's probably a bandaid. While now Im stable with the white plastic props, the CF props are just crazy town now Can't make it a 2 seconds without it flipping on is side or back.

The white props are doing fine, but I;m getting some minor funkiness in control, going up will ALWAYS start with a the forward right prop going up and the back left one going down. The harder I go up, the more that happens. Both of those motors we're significantly hotter at the end of the fight. Just by feel, it seemed like the Front Right was a bit more vibrating the the rest. I swamped the props between the two, same effect on that pitch. (thought it might reverse).

The other NEW thing is a tendency to want to yaw to the left. Since I've just saw it on the last fight, Ill hold on that being a issue, maybe just a calibration issue.

GPS - Just looked at that link. I think the "Anti-Interference Technology" is mostly sales hype. What it probably translates to is spread spectrum technology. I don't know any manufacturers that don't say something like that for their SS systems. I will say that if a single manufacturer could make both the radio system and a wifi/camera system (both on 2.4GHz), they would have a unique opportunity to select a spreading algorithm for each that would not overlap.

Jonas - I wouldn't consider adjusting the gains ad "probably a bandaid". There is absolutely nothing in the system that is more important or critical than the PID loop adjustment and anything you do that changes the dynamics of the system impacts those settings. No matter what you do, you should always expect that changing weight, balance, props, motors, etc. will require retuning of the PID. I really think you could save yourself a lot of frustration if you'd get that gain adjustment routed to the slider. This is not a programmable or soffware routing function, but rather requires you physically (cable) route the slider channel (now going to gimbal tilt I think) to the X1 or X2 input of the NAZA and then clicking the box in the software to activate the remote gain function. It really shouldn't be difficult and it makes tuning super easy (well... as super easy as tuning can be). What you want to do is determine the optimum tuning for both props so you can quickly reprogram when you change props. There is never going to be a setting that really works right for both. I've got the same problem as you when I switch. The settings for my white props will do nothing but flip over and crash when I install the carbon props. It's just to big a change in flight dynamics for any one setting to accomodate.

...Tiger