[TinyStego]

I set up a quad with the Revolution and the next branch firmware/GCS and the attitude mode works nearly flawlessly. It is so fun and easy to control! The only thing is now I want to get the quad to stay at an altitude for smooth recording of videos. I checked to see if the barometer was giving wrong readings.

With the quad on the ground, and looking at the altimeter on the firmware tab, the small hand stays on 6, and the big hand fluctuates between 0 and .5. When I lift it up a little it fluctuates between 1 and 2, and so on.

I checked the barometer readings in the system tab, and everything would fluctuate, but very marginally. Like less than one for alt, temp, and pressure.

When I lift of in stability 1 which has manual throttle, then switch it to stability 2 which has alt hold, it will throttle up a bit, then go lower, then throttle up just below where it was, then start going lower and lower. It kind of acts like it is using manual throttle, but it isn't.

When I put it into alt vario, it doesn't hold when I move throttle to middle. It'll go slightly up or slightly down, but won't stay.


What can I do to configure the altitude hold? I looked at the wiki and all it says is the altitude hold configuration should have tooltips showing what everything does, but it doesn't.

I would post my config, but I don't know how to extract it.

[Mateusz]

Please log in to see attachments and see this post by @liftbag https://forum.librepilot.org/index.php?topic=1221.msg9104#msg9104 also read other posts from the beginning.

There are two PIDs (control loops) one is stabilizing, and the other is controlling altitude if you set AltiHold or AltVario thrust mode. However, default parameters for that second control may be good for one aircraft, but for other for example more powerful quadcopter tunning might be needed (there is nothing that works for all aircrafts).

If problem persists, check if foam is not too thick, or to thin, check if baro is protected from propellers (in a case) and that case is not transparent. As in the link I attached  in the same thread MS5611 baro is sensitive to light.

Other issues that may affect stability in altitude hold are too high vibrations, or stabilizing PIDs (first control I mentioned) causing small oscillations/wobbly if not tuned right. First PIDs should not lead to jumps in altitude from my experience, but could introduce shaking image if they are way off.

I think that's all you should know to set it right.

[TinyStego]

Thanks for all of the info! How can I tell if the board is experiencing a lot of vibrations? Will the accel scope give me a clue?

[TinyStego]

Also, by foam do you mean foam tape that the Revo is on? I have it mounted on 2 strips of foam tape because that is what the person in the hobby store recommended.(I wanted something cheap and simple at first)

The Revo is in a black case.

[Mateusz]

Yes you check scope, but at vibrations I would look as last thing now.

You are NOT suppose to use sticky tape on baro as that could damage sensor by leaving dirt or glue residues inside. 

Air has to be able to reach sensor, but it has to be protected from wind blowing from propellers and light. You would use porous foam/sponge that air can go freely through.

As on the picture under Pressure sensor https://librepilot.atlassian.net/wiki/display/LPDOC/Altitude+Hold

[TinyStego]

So it doesn't matter that I have a case on it? Also, I'm going to include a few pictures of my set up. http://imgur.com/a/G9eAc
(It wouldn't let me upload directly for some reason:( )

[Mateusz]

So it doesn't matter that I have a case on it? Also, I'm going to include a few pictures of my set up. http://imgur.com/a/G9eAc
(It wouldn't let me upload directly for some reason:( )

I haven't heard about anyone using it without sponge. Barometer is sensitive to strong wind (especially from propellers) and light. So piece of sponge helps to protect it from those factors, while still allowing enough calm air to come into the sensor. Case alone might not be enough as blowing propellers and light can still hit the sensor if there is no sponge.

Did you already check VerticalVelocityPIDs ?

[liftbag]

A properly designed case should have a foam holder for baro sensor.

[TinyStego]

So it doesn't matter that I have a case on it? Also, I'm going to include a few pictures of my set up. http://imgur.com/a/G9eAc
(It wouldn't let me upload directly for some reason:( )

I haven't heard about anyone using it without sponge. Barometer is sensitive to strong wind (especially from propellers) and light. So piece of sponge helps to protect it from those factors, while still allowing enough calm air to come into the sensor. Case alone might not be enough as blowing propellers and light can still hit the sensor if there is no sponge.

Did you already check VerticalVelocityPIDs ?

Can I use just a regular house sponge? I have plenty of those lying around.

And yes I checked them, I put in the values that were listed in the screenshot, hopefully it will work. I won't be able to test it until the morning.

A properly designed case should have a foam holder for baro sensor.

Unfortunately, my case does not have that. I'm hoping the case will be able to the the sponge/foam on its own.

[Mateusz]

Unfortunately, my case does not have that. I'm hoping the case will be able to the the sponge/foam on its own.

When you find the right settings for Altitude Hold (Vertical Velocity PIDs) after playing with them. Post your motors/props/esc/frame size/battery/total weight and those values if you get good alt.hold. It might be very useful for people around forum with similar copter

[TinyStego]

I will do that! Anything to help contribute to the community.

I do have one more question for now though, will I be able to use a normal household sponge? I don't know where I could find a porous foam locally. I'll check Ace and Home Depot to see if they carry it, but it would be nice to just use something I have lying around.




Hopefully soon enough I'll posting more answers than questions 

[Mateusz]

Usually car/dish washing sponge is porous/spongy, so it must also allow air to flow through it.
If the pores/holes in the sponge are large enough you can try it. Just make sure air can flow through it.
There is a picture in the link of the sponge people use on Revo.