Parameters that can stabilize the helicopter in pos hold and auto states

As I made the helicopter, I had many questions.
Some of them have been solved by my efforts.
Others are still questionable.
I do not know why, but there are many things that have been resolved.

What I would like to ask you about today is the parameter.

What parameters do you modify if the helicopter shows unintended movements in modes such as auto, poshold, and althold?
(For example, when the altitude of the helicopter suddenly goes up or down, or to the left or right)

If you look at DJI’s quad-copter, such as a phantom or an inspire, these are very stable in hovering in gps mode.

However, my helicopter does not stay in poshold, althold, or auto mode.
I see unintentional movement.
Sometimes the altitude gets lower, and it flows to the left or right.

Is this normal and can not help it? Or are there any parameters to overcome these problems?
Or is this a hardware problem, such as a heli frame or engine?

This is very difficult to say for sure. The best would be if you have a log of a flight where the helicopter is hovering in perhaps Pos Hold with no stick inputs, and is displaying the erratic behavior. The log from the SD card is most helpful for your described problem.

Thanks Chris
You always help me a lot.
This is a very big fortune for me.

I will attach B Log and T Log on the next flight.

And this is the log yesterday.

The helicopter lost his position.

This can be seen at 92.96% of the data flash log.


Certainly the helicopter is recording a great vibration.

However, even if I recorded a larger vibration than this, there was no problem with the flight, but this is the first time I have seen this problem.

I think this problem has been caused by vibration, what do you think, Chris?!2AYVzQYQ!z2m33cFhpNR7utGDZ_GNxQ

Well, it does look excessive to me. I’m seeing an average of about 70 or so on the X-axis in flight. Almost like the controller is loose in the frame or something.

I guess I’m not sure what the recommendation is for 3.6. My helicopters always exhibit high vibration on the ground during runup but they smooth out once everything comes up to speed and the machine lifts off. This is from one of my gas helicopters with a CUAV V3x, hovering in Pos Hold. I was told this is way excessive and no way the EKF can handle it. So I’m not totally sure if there is new recommendations for 3.6, or what. I’ve flown this helicopter since last July with this vibration level and never had a problem with it in 3.5.

As far as I can see, nothing has changed as far as vibe recommendations in the documentation. So I would see if you can get the vibration below about 10 on all three axes. Maybe you have blades out of track, tail rotor out of balance, bearing out of the tail rotor driveshaft, bent mainshaft? It seems like a lot, almost indicates a mechanical problem someplace.

The vibration of your helicopter looks very beautiful.

I used a gel pad to absorb the vibration, but it was useless in front of the engine chopper’s vibration

Do you have any recommended damping method?

I am on the next flight

Let i try to touch two parameters

I’ve read the explanation, but it’s still very difficult for me.
(In fact, I did not really understand what this meant)

Your feedback is very important.
I’ll take a physical approach.

When I used pixhawk2, there was excessive vibration, but the flight was good.

I switched to pixhack v3 and this is the first dangerous thing.

I think I would look it over mechanically and see where that vibration is coming from. I have a CUAV V3x mounted in one gas helicopter with no vibration isolation at all. It is stuck to the FBL unit tray with outdoor mounting tape. And even that one is below 15 on three axes, and Z is the highest

Most of the time, assuming nothing else can be found, it’s due to a rotor that was tracked static, but doesn’t track dynamic. Tracking those is more of an art than a science. With full-size manned helicopters we have the RPX DynaTrack that shows which blade number is not tracking and how much high or low it is. So the helicopter comes in and it’s like it’s got a build in stick-shaker in it, but we can track the rotor on those until the helicopter won’t make the water ripple in a glass sitting on the center console in flight. That kind of technology doesn’t exist for RC, so it’s more trial and error to find the sweet spot. I’ve spent 5-6 hours tracking a rotor on RC to get it perfect :grinning:

Thank you
I was relieved that it was a problem that could be solved with time and my efforts.

@Ricoman Could you post a picture of your Pixhack V3 on your helicopter? I think it might help if we could see how and where you have it mounted. Where you have it mounted can have a big impact on vibrations as well. It should be mounted on a fairly rigid part of the structure, otherwise the vibrations of the helicopter could be worsened by the structure. Also, if you want to see if it is a blade balance or track, I think you could look an FFT of the vibrations. Certainly a blade balance would be shown by a high 1/rev spike in the x or y accel. I think a blade track issue would be shown in the z axis by a high 2/rev spike (not sure about this one). use this link to learn how to measure and analyze vibration data. Post your results if you want me to help analyze the results.
First thing though is please post a picture of your setup!


Bill !! It’s been a long time.
Thank you for always asking questions.

Unfortunately, this is the time to

It’s 23:00 on Friday in Korea.

I am on a business trip now

I’m afraid I will not be able to upload until next week.

Could you tell us what kind of helicopter it is, and where the controller is mounted on it?

I think the x-axis is fore and aft vibration, that’s why I wonder. y is side to side, z is vertical. I think. It is unusual to have x higher than everything else.

A gel pad like you are using should certainly damp the vibration pretty good. But if the helicopter exhibits high vibration levels, my opinion is that you should track down the mechanical cause and not try to “patch it” by providing more isolation for the controller mount. A helicopter that vibrates badly will shake itself apart eventually and cause excessive wear on it, and stuff coming loose. I don’t know if this is a piston, electric, or what. There is common things in both that can cause vibration to be high. But pistons have separate things like the engine being out of alignment with the clutch, or even engine tune that can cause excessive vibe. Some piston helicopter engines come from the factory horribly out of balance and the engine itself shakes, and this must be corrected or the helicopter will have a short service life. And no matter how you damp the controller to try to mitigate it, you’ll never be able to use a camera payload on the machine if you don’t fix the source of the vibration.

The chopper of the log I sent is sab goblin 700.

fc is pixhack v3
Controller futaba 14sg
Receiver uses r7008sb

My fc is mounted in a red circle.

So is there any other components or wiring touching the case of the pixhack. It looks like you got a lot of stuff back there.
Edit: I guess this isn’t a picture of your helicopter specifically. Looks like a stock photo from a website. But the questions are still valid.

Yes, this is not my helicopter.
I am in another place because of my work.
Because of that, I could not take pictures of my helicopter, so I have inevitably pulled pictures from the internet.

I assume your helicopter is electric? That is the right place to put the controller. It is the normal place for the FBL unit on a Goblin 700.

One thing to check on those is the tail belt tension. Make sure it is plenty tight, otherwise the belt will cause quite a bit of vibration in the tail boom assy.

Thank you.
I am now away from my helicopter.
I will confirm tomorrow and I will tell you again.

Hello Chris
long time no see
I have had so much work that I could not care less about the helicopter.

First, I checked the tension.
We were maintaining sufficient tension.

I do not have enough equipment and knowledge, so I do not think I’ve balanced the rotor enough

After facing the helicopter and aligning the pitch of the rotor, we rotated the main shaft to balance the rotor on the opposite side
We also adjusted the length of the linkage.

I do not think this is the way to balance the rotor balance you’ve been talking about.

How can I match the rotor balance you have said?

The blades normally have to be balanced off the helicopter. There is tools made for doing this, and various videos on the internet on how to do it.

What I was talking about is blade tracking. What I like to do is hover the helicopter against a dark background that makes it easy to see the edge of the blade disc. I’ve tried the different color tape on the blades and that don’t really work for me. If I have a blade flying high or low I land the helicopter and mark one pitch horn with a marker and adjust the pitch link on that one. Then hover it again. If it gets worse, turn the pitch link the other way.

When I get the blade disc nice and sharp looking in hover, then I go to the ground station and look at the Z-vibes. And tune that pitch link a 1/4 turn at a time either way until I get the lowest Z-vibes.

Sort of a “poor man’s” DynaTrack. Just like we usually find with the big ones, the lowest vibration is not always where the blades track exactly perfect.

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Did you ever get this to work? Willing to share some pictures?