Muskoka

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"Bounce" coming out of a flip or roll
« on: February 02, 2016, 08:41:28 pm »
Hi folks, quick question. My buddy and I both have the Totem 250 X quad, and it flips/rolls great with Libre. The only concern is the slight "bounce" when it's completing (coming out of) the 360 degree flip or roll. It's nothing major, and isn't so bad that the quad gets out of shape, it's just something we observed, and wonder if there is some way to tweak it out.

Were observing this in rattitude mode with cruise control, with rate at 700 degrees per second. It does it and all rate settings, just were at 700 now.

I'm also flying a f330 with close to the same settings as the 250 and it doesn't bounce at all. Is it strictly a mass/size issue, the 250 being that much lighter?

Thanks for any thoughts, input.

f5soh

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Re: "Bounce" coming out of a flip or roll
« Reply #1 on: February 02, 2016, 08:46:26 pm »
To remove the bounce you should tune PID. See the Easytune feature.

Take a look also to the Attitude "P" factor, maybe reduce a little.

Muskoka

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Re: "Bounce" coming out of a flip or roll
« Reply #2 on: February 02, 2016, 08:51:38 pm »
We've both used Easytune, and they fly great, solid as a rock in flight. Hate to mess up regular flight just to get the bounce out of flips/rolls. I also used Easytune on the 330 and it flies just as tight, but no bounce coming out of a flip or roll.

The Outer Loop pids are still the default of 2.50 (on my 250 and 330), are those the values you're suggesting we lower for pitch and roll? Again, my 330 is fine, just stating it's on default as well for the Outer loop.

« Last Edit: February 02, 2016, 09:05:10 pm by Muskoka »

Re: "Bounce" coming out of a flip or roll
« Reply #3 on: February 02, 2016, 10:58:16 pm »
Adding a little D gain will help with the bounce. But may dull the response. To high P gain may have the same issue. Adjust P till it barley bounces then add some D to get rid of it
5" alien 4s 596grams with battery and GoPro FPV
Lantian LT210 4s 604grams with batt and GoPro FPV
GE X220 4s 6" 513grams with batt and HD cam FPV
Homemade acro X copter. 6" 4s - like a warpquad LOS

Muskoka

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Re: "Bounce" coming out of a flip or roll
« Reply #4 on: February 02, 2016, 11:58:06 pm »
Ran Easytune again and here are the numbers for Rattitude mode using Cruise Control. It flies real nice, and flips / rolls great, but still has a bounce at the end of a flip or roll. Not a big bounce, but it's there. It should be crisp, as in snap over, and stop, and it's not. No amount of tweaking the pids seems to get rid of it totally. Again, it does not exist on my 330.

Easytune Numbers:

Roll and Pitch Inner Loop Prop .00713 Int .02496 Der .000096
Roll and Pitch Outer Loop Prop 2.5 Int 0 (Defaults)

These numbers are a long way off from the defaults for a "Generic X Quad". But there what Easytune is giving me.

I've tried Easytune from .00300 to .01000 on Proportional, and accepting the values it spits out for everything else, it makes no difference. It's not a huge deal, it's flying great, but that bounce is annoying.

With these numbers it's right on the edge of oscillating, actually does a bit with quick stick movements. If I go lower than these values the bounce is worse, again not horrible, but more than with the numbers above.

I should add,  I've been trying acro+,  and it flips real fast, but I don't think there is a bounce it that mode,  but everything happens so quick it's hard to see for sure. I'm thinking the bounce is a cruise control issue myself,   like it's applying too much trust at the end of the flip, thus causing a "rebound",  bounce. No cruise control in acro+.
« Last Edit: February 03, 2016, 12:45:43 am by Muskoka »

Re: "Bounce" coming out of a flip or roll
« Reply #5 on: February 03, 2016, 03:55:58 am »
I think it's the transition from rate to acro+ and back to rate. In rate it's using the PID loop to handle the quad when in acro plus I don't think it uses any of the PIDS and goes full manual. That's why it's only used for really fast flips. It's to be able to use low rates and still get fast flips. Try using just RATE mode with like 5-600 degrees a second and like 66-75% expo. Also you may be exceeding your setups ability to stabilize your quad. Some escs just arent up to the tasks of really high rate moves then sudden stops.
« Last Edit: February 03, 2016, 03:59:24 am by NicholasDavid »
5" alien 4s 596grams with battery and GoPro FPV
Lantian LT210 4s 604grams with batt and GoPro FPV
GE X220 4s 6" 513grams with batt and HD cam FPV
Homemade acro X copter. 6" 4s - like a warpquad LOS

Muskoka

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Re: "Bounce" coming out of a flip or roll
« Reply #6 on: February 03, 2016, 02:07:53 pm »
Thanks for the input guys, but I'm pretty sure were not on the right track yet. If it's a pid issue it's a problem. You can't tune pids for normal flight, getting that locked in feel when flying, and then have to re-tune your pids for flips and rolls in the same "flight mode", because it can't handle a flip properly. That just doesn't make sense. If the pids are good, they're good, and should handle every aspect of flight. We've both been flying for years, everything, so were not knew to setting things up. But we are new to "CC3D" and Libre Pilot in the last few months.

Raining today so I can't test but I'm sure it's the cruise control causing the issue. Like I said, I have my 250 setup almost exactly the same as my 330, same flight modes, same rates, both setup using Easytune, yet the 330 doesn't bounce. And when I say bounce, it's more like a "shake" with a hint of upwards thrust. It's like something needs to be smoothed out with the amount of force/thrust that's being applied (by cruise control) at the end of a flip, because it's really not noticeable in acro+.

Ok, so no pid loop in acro+ (?), but more important I think is there's no cruise control in acro+. Cruise control works fine on my heavier 330, but not so well on either of our 250's. Still say it's a weight issue, and the way cruise control is working.

Were having a tough time deciding on which setting in cruise control to "test" with. We're thinking the "MaxThrust" might be the one, but we're just guessing. It say's 80-90 for multis, and we're both still on 90. Maybe lowering that value will apply a little less thrust coming out of the flip or roll and will alleviate the shake/bounce in our lighter quads? How will lowering that value affect regular flight?

If that doesn't work I guess we'll just have to get away from using cruise control. We both can fly in any flight mode, that's not a issue, but being new to this controller we like to try everything it offers. :)

Muskoka

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Re: "Bounce" coming out of a flip or roll
« Reply #7 on: February 03, 2016, 02:50:36 pm »
Here's a short video from the other day with a Mobius strapped on showing what were talking about. The bounce / shake isn't extreme but you can see it, and hear it.


f5soh

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Re: "Bounce" coming out of a flip or roll
« Reply #8 on: February 03, 2016, 06:50:17 pm »
First tune in Rate (inner loop), i see your PID numbers are the same in Roll and Pitch a this should never appends because the weight are never the same in Roll /Pitch axis.

Try to reduce the Attitude Proportional OuterLoop, this can give this result i see in your video assuming you are in Rattitude.

Acro+ is rate around center stick and manual at full stick: Manual means motors are "connected" directly to stick demand without any Gyroscope limitation or stabilization.

Muskoka

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Re: "Bounce" coming out of a flip or roll
« Reply #9 on: February 03, 2016, 07:03:51 pm »
It's a fully symmetrical "X" quad, not a "H", roll and pitch are the same, weight is balanced evenly, it's fine, and the way it should be. It flies great so the inner pids are tuned just fine. I've already adjusted the Outer Loop from the default of 2.5 for pitch and roll to 1.0, didn't change anything with regards to bounce. Just tried with Cruise Control off, that didn't make any difference either.

The only flight mode where it's hardly noticeable is acro+.

Ok, just tried something else. I lowered the rate for roll and pitch in Rattitude from 700 to 550 and it seems a lot better. But of course now the flips and rolls are no where near as tight. Outer loop pids at 1.0 for roll and pitch still.

I've only tried PwmSync and Pwm at 490 as these Emax simon series esc's aren't capable of oneshot without flashing. Really shouldn't make a difference though, it flies great.

We're going to leave it for now. Fly them, and just accept the way it is. Lower the roll rates, little to no bounce, higher rates, accept a bit of bounce. No biggie, thanks guys.
« Last Edit: February 03, 2016, 07:53:06 pm by Muskoka »

f5soh

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Re: "Bounce" coming out of a flip or roll
« Reply #10 on: February 03, 2016, 08:22:54 pm »
Your quad can be H, X or + the weight are never symmetrical.
If your battery is a rectangle (is really a perfect cube ?)  and placed in Pitch axis this cause bigger values needed for Pitch axis.
If you still see rebound in Rate or Acro+ you should tune the Rate (inner loop) first.

OneShot give better response and motor braking, most of the time PID are higher.

Muskoka

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Re: "Bounce" coming out of a flip or roll
« Reply #11 on: February 03, 2016, 08:34:44 pm »
Yes the quad is perfectly balanced symmetrically, if the battery is placed diagonally across the quad, corner to corner, like it is. Symmetrical quads can always been tuned with same pitch and roll pid numbers, they have to be. Laws of geometry say so.   ;) Anything other than a symmetrical "X", ok, but it's a non issue with a symmetrical quad.

And like I've stated numerous times, it flies great. If the pids were out it wouldn't fly great. And, my 330 is setup exactly the same way, using the same techniques, and it flies and flips great, it's only the lighter 250 that has a slight bounce in a flip or roll. My 330 escs are Oneshot125.

Like I said, not a problem, we'll live with it.

Thanks again.....
« Last Edit: February 03, 2016, 08:41:45 pm by Muskoka »

f5soh

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Re: "Bounce" coming out of a flip or roll
« Reply #12 on: February 03, 2016, 08:45:40 pm »
Well, seems you know exactly what you are doing. Please consider i try to help you.
Not only "geometry laws" are taken in account but also inertia and more "laws".

A small example without rebound taken from test flight using a almost well tuned quad, most of them take 0.5s so around 700deg/s



Please post a picture of your symmetrical quad.

« Last Edit: February 03, 2016, 08:54:20 pm by f5soh »

Muskoka

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Re: "Bounce" coming out of a flip or roll
« Reply #13 on: February 03, 2016, 09:07:37 pm »
I know your trying to help, thank you. And yes, neither one of us are new to flying or setting up anything rc, but we are new to CC3D (last 2 months). I've flown a Vector, Naza Lite, Naza V2, Tarot, and KK2. Were not new to this, or pid tuning. :)

We're both flying these Totem 250's. My 330 is exactly the same, and has no issues. Here's mine upside down with battery attached. The sat is under the front, opposite to battery leads, balances fine, front to back, side to side.
« Last Edit: February 03, 2016, 09:27:13 pm by Muskoka »

f5soh

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Re: "Bounce" coming out of a flip or roll
« Reply #14 on: February 03, 2016, 09:20:54 pm »
Just attach a picture of your quad, no need a frame picture but your quad RTF.

I you can see the difference from your flip video and mine, you are able to tune properly your quad and matches the same behavior while your quad rotate and stop without rebound.