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What should I use for ATC_RAT_PIT_FLT* values?

I have just installed Copter-4.0.0-rc2 so I can use the harmonic notch filter and I am working through the recommended settings in “Tuning Process Instructions”. In that document it refers to ATC_RAT_PIT_FILT, which I need to set to 14.5, but the nearest I could find in the Parameter List for release 4 are these 3 items:

image

Is it as simple as making ATC_RAT_PIT_FLTD and ATC_RAT_PIT_FLTT equal to 14.5 and leaving ATC_RAT_PIT_FLTE at 0?

And similarly for ATC_RAT_RLL_FILT - it has been replaced with:
image

And similarly for ATC_RAT_YAW_FILT - it has been replaced with:
image

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How big is your copter? Generall R/P FLTD&FLTT should be set to what yo had as D filter in 3.6 - on my small copters I set it to 80hz and have GYRO_FILT at 100Hz

It is a quadcopter at 520mm diagonal with 13" propellers. From the graphs in “Tuning Process Instructions”, then INS_GYRO_FILTER should be 29 and ATC_RAT_PIT_FILT should be half of 29, or 14.5.

I am not sure what you mean by “D filter”? Could you give me the full parameter name?

These are the 3 values from release 3.6 that I am trying to set in release 4.0:

ATC_RAT_PIT_FILT = INS_GYRO_FILTER / 2 = 14.5
ATC_RAT_RLL_FILT = INS_GYRO_FILTER / 2 = 14.5
ATC_RAT_YAW_FILT = 2

But release 4.0 has those extra new parameters in the screen-grabs above …

This is what I suggest:

ATC_RAT_PIT_FLTD = INS_GYRO_FILTER / 2 = 14.5
ATC_RAT_RLL_FLTD = INS_GYRO_FILTER / 2 = 14.5
ATC_RAT_PIT_FLTT = INS_GYRO_FILTER / 2 = 14.5
ATC_RAT_RLL_FLTT = INS_GYRO_FILTER / 2 = 14.5
ATC_RAT_YAW_FLTE = 2
ATC_RAT_YAW_FLTT = INS_GYRO_FILTER / 2 = 14.5

OK, thanks @Leonardthall:slightly_smiling_face: When the weather here improves, I will have another crack at getting the Autotune to complete its task.

Are you sure of this? Is the first time that I read to set FLTD for YAW instead of FLTE.

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@Taipan Sorry I made a mistake and corrected it above.

@anbello Thanks for correcting my mistake!!!

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Would be good to add that in the tuning guide.

Thanks

Harald

Yes, that will all be done as part of the 4.0 release.

As always we would appreciate any help we can get to update the wiki faster or with better presentation.

I can see the logic for these new parameters but am unsure how to correctly use them. Was updated documentation for this released with 4.0? I am struggling to find any mention of these new parameters. All the docs I have relate to the older parameter. I am setting up a large x8 and need to be sure the values are correct.

We are going to add this:

3.6:
ATC_RAT_PIT_FILT - INS_GYRO_FILTER / 2
ATC_RAT_RLL_FILT - INS_GYRO_FILTER / 2
ATC_RAT_YAW_FILT - 2

4.0:
ATC_RAT_RLL_FLTD - INS_GYRO_FILTER / 2
ATC_RAT_RLL_FLTE - 0.0
ATC_RAT_RLL_FLTT - INS_GYRO_FILTER / 2
ATC_RAT_PIT_FLTD - INS_GYRO_FILTER / 2
ATC_RAT_PIT_FLTE - 0.0
ATC_RAT_PIT_FLTT - INS_GYRO_FILTER / 2
ATC_RAT_YAW_FLTD - 0.0
ATC_RAT_YAW_FLTE - 2
ATC_RAT_YAW_FLTT - INS_GYRO_FILTER / 2

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@Leonardthall Thank you for the clarification. Most appreciated.

What process or procedure should people then use to determine the best value for INS_GYRO_FILTER ?

I think there are two questions here:

  • how high does it need to be to be flyable. I think the wiki suggestions here are correct
  • how much higher could it be to achieve greater control. I think this is going to be based on more than just the prop size, motor size, vehicle mass and others will all make a difference, but similary too high on a poorly constructed craft and you are going to get a lot of motor heat. So probably not a question with a single answer.

I’m using 30inch propeller with arducopter 4.0.0 HEXA configuration. What is the suggested INS_GYRO FILTER value?

Default value is 20hz now and ATC PIT & RLL _FLLT & FLLD value also 20hz.

That’s probably fine

Then it’s not necessary to have the value like this
ATC _PIT&RLL FLLT FLLD= INS GYRO FILTER /2

IF this the atc value from my case is 10hz right.

Are there use cases these parameters needed to be customized in a different way?
I mean, why not just to set INS_GYRO_FILTER, and all other _FLTT & _FLTD will be calculated automatically :slight_smile:

Yes, there are cases when they should be customized.
You can increase them for better performance, up to a point.
On my small copters my gyro is 100, and filtd, filtt are 90.

As a developer it is easy to make the mistake of thinking you know better than the users. The problem is that as soon as I make a decision to hard code a relationship like this it ensures the users can’t show me that I don’t know what I am talking about. :slight_smile:

There are always exceptions to the rule, even if it is a good starting point. Keep in mind that these PID object are used to fly a huge range of aircraft.

Keep in mind the reason for the FLTT filter is to reduce the noise from the lower update rate of the RC input and the EKF bias corrections at 100 Hz. That is why I try not to increase the FLTT filter above 20 Hz. Depending on the aircraft this may not be practical but it is something to keep in mind.

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