Rate KP and Stab KP

Posted by Mark Slater on March 22, 2012 at 12:10pm

I've been tuning the octocopter this evening, I started with Stab at 1.000 and Rate at 0.25.

I tuned the rate by hovering then giving sharp stick inputs and watching for the bounce as I release the stick to centre. I turned up Rate P until the bounce was just present then back down a little so no bounce on releasing the stick.

During this I found the controls very wolley and needing loads of stick input.

Moving on to STAB I increased it via channel 6 up to 2.8 (still got to get this right but waiting for batteries to charge now)  As I increased STAB the sticks became much more responsive, The octo seems fairly good until wind catches it then its a bit of a sod to control.

Am I doing this correctly, how do I got about tuning yaw ?

This oct has loads of power, it lifts at quarter stick so I expected the values to be less than default but If I remember correctly default rate was somewhat less than I have now,

Any help would be appreciated.

Thanks

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Replies

  • Mark Slater March 24, 2012 at 8:12am

    I'm having a night mare ! 

    I'm doing something wrong in tuning, but I don't know what. I thought I had the Rate dialed in but as I add stab its becoming unstable, so I reduce rate and get some stability back but that effects return to level it stops way short of being level after centering the sticks. 

    I did get to a stage when rate P was at 0.15 and Stab at 1.6 where there was no wobble but I was at full stick just to correct the hover.

    So here's my tuning method, please tell me where I'm going wrong. All tuning is done in Stabalise mode.

    1. Set a base value of Rate 0.25 Stab 1.0

    2. Adjust Rate P and put in a sharp stick movement then stick back to centre. Watch for a wobble as it returns to level. Reduce Rate P until the wobble just disappears.

    3. Begin to increase STAB and repeat the same procedure

    and thats about as far as I've got. Its a perfectly still day here and Ideal for testing.

    Help would be appreciated, I've obviously got something very basic wrong in my method.

  • Developer
    Adam Rivera March 22, 2012 at 1:19pm

    Mark: I fly a large octo as well. Your rate looks pretty spot on. You should set your stab_i gain to zero and focus on getting stab_p dialed in. stab_p is around 1.75 for my octo. Once you get that where you want it, you can play with trading off a little (like .01 at a time) stab_p for some stab_i for better response in wind or with cg issues. You definitely shouldn't be tuning all your stab response into the Stab_I gain though. Start with P.

    Stab_I will help in the wind. Just to be clear, stab_i is how quickly the copter adjusts for wind / CG, and stab_i_max is how much it is allowed to correct for wind/CG. So if you get stab_i dialed in to where it is correcting with the appropriate speed and it still isn't quite correcting enough, you can increase stab_i_max. Maybe start with increments of 5 on stab_i_max.

    I am flying 14x4.7 props with AXI 2826/12 motors (LOTS of power), but I still require a higher rate_p setting because of the sheer size and weight of the copter. You are correct in having your value a little higher than the defaults.

    Good luck!

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