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HelicopterMain Discussion › PID gain explained
05-15-2017 04:40 AM  40 days agoPost 1
heliraptor10

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kokomo, in-US

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I feel like the pop up help bubbles in the ikon software probably explain this but I didn't understand until this video.

Watch at YouTube

Goblin! where have you been all my life?
RC helis, the original fidget spinners

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05-15-2017 11:08 AM  40 days agoPost 2
steve9534

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yakima, wa.

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Control theory

Excellent. Thank you

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05-15-2017 01:20 PM  40 days agoPost 3
Four Stroker

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Atlanta

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Look up Ziegler-Nichols Tuning of PID controllers on youtube. This is a practical way of picking gains developed in about 1928. It is extremely unlikely that 3D sponsored pilots use the linear systems theory that goes with PID loops.

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05-15-2017 01:39 PM  40 days agoPost 4
heliraptor10

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kokomo, in-US

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What PID does in a fbl is a little different,
But I didn't understand why we needed different gain settings. I've watched several videos on fbl set up and still didn't understand what the proportional integral and derivative were.

I was just happy the ikon wizard made it so you didn't have to understand.

Now I'm thinking I can go back into the settings and tweak my birds within an inch of their lives.

Goblin! where have you been all my life?
RC helis, the original fidget spinners

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05-15-2017 02:27 PM  40 days agoPost 5
Four Stroker

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Atlanta

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Well you can play with them to within an inch of your life. There are no optimal values. All three are a tradeoff.

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05-15-2017 02:43 PM  40 days agoPost 6
heliraptor10

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kokomo, in-US

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I'll leave cyclic alone
Coming from flybarred I was super nervous about my first fbl controller. The idea of something being set wrong causing the whole heli to pitch or roll without input scared me. But the cyclic performance has always been perfect to me.

Now while the tail holds better than any other gyro I've flown, there's a tiny tiny bounce that I've lived with. Time to get that Bluetooth set up and do some set up at the field.

Goblin! where have you been all my life?
RC helis, the original fidget spinners

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05-15-2017 04:50 PM  40 days agoPost 7
Heli Fanatix

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Fountain Valley, CA

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The defaults FBL values now-a days are good enough for 95% of the pilots out there ... even some of the pro's don't need the last 5%.

It's always good to want to learn, however each individual's teachability is different (It's how they can relate) The setup wizard does make things simple and that is the key.

Sometimes knowing a little bit let's you be dangerous.

To be fair, I use the HC3-SX with 2013 firmware. Yes it was expensive ... and so are crashes / time spent on repairs. I value time over money. I than got lucky with additional bonus! A very good FBL that was extremely versitle! Beginner all the sa to speed flying. I Used the stock settings and did what ever I needed to do. Spent time flying and advancing and not "TWEAKING"..... it's our skills as well as our choice product we use. I've tried other FBL ... they don't fly the same even though they are on the same heli.

Couple years later, my flying progress and so has my understanding of PID, gains, features ... I can't get much more from all my FBL

- Scott

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05-15-2017 07:21 PM  40 days agoPost 8
heliraptor10

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kokomo, in-US

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I flew forever on my g500 after going through the wizard,
Before playing with any of the advanced settings.

I did have the servo frame rate too low that whole time, but when I got it right those 40$ hitecs weren't too shabby. Of course after I put BK's in there I was real happy.

Goblin! where have you been all my life?
RC helis, the original fidget spinners

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05-16-2017 05:42 AM  39 days agoPost 9
Pistol_Pete

rrProfessor

Seffner, FL

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I learned with Gary. Was fortunate to get his rought draft before the edited print.

http://www.modelaviation.com/GaryWright

For an in depth using helis, check this out

http://www.rchelicopterfun.com/pid-basics.html

~~Enjoying the hobby one flight at a time~~

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05-18-2017 11:42 PM  37 days agoPost 10
EEngineer

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TX

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So you've been "PID"ling around, eh?

Logo 600SXs, 700XX, 800XX

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05-20-2017 12:10 AM  36 days agoPost 11
TheMainShaft

Heliman

Southlake, TX - USA

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I was critically damped once. I would not seriously trust any auto manufacture to reliably implement something as complex as this. I will not purchase a self driving car until they fully implement the "UNDO" button.

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05-20-2017 12:50 AM  36 days agoPost 12
EEngineer

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TX

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You'd best check with revmix for the "truth" on that subject.

Logo 600SXs, 700XX, 800XX

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05-20-2017 10:10 AM  35 days agoPost 13
Heli_Splatter

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Silver Spring, MD by way of Sidney, Ne - USA

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Excellent post.

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05-20-2017 06:44 PM  35 days agoPost 14
Flyin for Jesus

Senior Heliman

Dana Point, Ca. 92629

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While that video showed things ( I didn't get any sound, did anyone else? )
I've done a bit of research and this is what I have come to conclude...
Algorithm with just P gain ( no I or D )
Heli is in a hover then introduce some wind from the side.
The heli leans say 3 degrees to the right. The FBL goes through one sample, sees the 3 degrees that was uncommanded and calculates based on the P gain value the response. Lets say is 1-2 so the FBL does a 6 degrees left aileron.
It samples again and say it 2 1/2 degrees off now so its response is 5 degrees left. Samples again 2 degrees off so it outputs 4 degrees left.
The flaw with P gain only is it will never get back to level. If it does happen to get level, the output is level and the wind will blow it off level again. But as it gets closer to level, the output gets less so it will eventually come to some equalibrium with say 2 degrees right and FBL output 4 degrees left will just stay there with the applied wind.

Now a PI loop ( no D gain )

Same as above, heli is blown 3 degrees right. One sample of the FBL sees the 3 degrees and gives 6 degrees left. I records the number of 6
FBL samples again and the heli is 2 1/2 degrees off so P gain says left aileron 5 degrees and the I recorded ( lets say I is 10% ) so it takes 10% of the recorded 6 so the FBL outputs 5.6 degrees left aileron and the I records the 5 + 6 from before.
FBL samples again, heli is 2 degrees off so P says 4 degrees left and the I of 11 and 10% add another 1.1 degrees so the FBL outputs left aileron of 5.1.
So what happens is the I gain keeps stacking up until the heli gets back level and when the FBL samples and the heli is level, the stacked up I values drop off.
Problem with this is the I drops off when the heli got back to level but the servos have to go to 0 position and the heli itself has some momentum so it will over shoot the level position then the cycle goes again but in the other direction.
Thats why the PI part of the video shows it zigzaging the center line.

Now the PID loop

Same as above. Heli 3 degrees right. P say do 6 degrees left. FBL outputs 6 deg left and I records 6. D records heli is 3 degrees off.
Next sample, heli off 2 1/2 degrees P says left ail 5 degrees. I adds 10% of the recorded 6 from previous sample so it adds .6 degrees. We are at 5.6 degrees left aileron the D says heli was at 3 off now its only 2 1/2 off so a difference of 1/2 degree of correction has occured. Say D is at 10% also. It actually removes 10% of the 1/2 degree the heli moved. So -.05 degrees from the D. FBL output is 5.55 degrees.
Next sample, heli is 2 degrees off so P says left ail of 4 degrees I ( same as above ) the 5+6 is 11 so it adds 1.1 deg so the same 5.1 now the D sees the same 1/2 degree correction and removes .05 degrees so the FBL outputs 5.05 degrees.

I'm not going to go way out, but as the I starts stacking up and the heli starts moving faster back to level, the D gain see the increasingly faster correction of the heli as the I keeps stacking up and actually removes some of the output correction.
Basically saying if the heli is not correcting, let the I stack up until you get the heli correcting. After the I stacks up high there is significant correction going on and the D will smooth down the rapidly increasing correction and keeps the heli from overshooting its level position.

Hows does this sounds for an explination?

CRAP!!! The first time I watched that, there was no sound. I thought it was odd. How can you understand from just watching the screen.
Anyway, watched it again and there is explination. However, I am not deleting my above post.

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05-21-2017 07:10 PM  34 days agoPost 15
Pistol_Pete

rrProfessor

Seffner, FL

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Did you get a chance to look at second link as well as video within it I posted?

~~Enjoying the hobby one flight at a time~~

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05-21-2017 07:47 PM  34 days agoPost 16
wc_wickedclown

rrProfessor

long beach calif

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awesome post

Insha Allah made in america

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05-22-2017 08:44 PM  33 days agoPost 17
heliraptor10

Key Veteran

kokomo, in-US

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I learned with Gary. Was fortunate to get his rought draft before the edited print.
http://www.modelaviation.com/GaryWright
For an in depth using helis, check this out
http://www.rchelicopterfun.com/pid-basics.html
Didn't watch the video yet,
But both of these links are good stuff.

Gary breaks down the PID into some basic if/then rules. I get the sense that this is from really early in the flybarless game.

Again thank the heli Gods for Ikon's wizard.

Goblin! where have you been all my life?
RC helis, the original fidget spinners

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