Throttle mid-point tuning?

[vpb]

Hi,

Multiwii Throttle MID & RATE really help changing altitude smoothly. I usally use 50-mid and 35-rate.

But I think it should be tuned, I mean you must find the correct mid point value where the copter holds it altitude (for a short time, without alt-hold activation).

I dont know whether there's a precise method that I can read the right value?

I'm using frsky telemetry with mw, and I can read the rpm value wirelessly. I think that the mid-point = (rpm value - min throttle) / (max throttle - min throttle) * 100. Is it true?

[copterrichie]

I agree. Because my copters are so heavy, I generally set my mid-point to about 60, the Expo will vary.

[vpb]

Yes, my Y6 is a bit heavy too, over 1.5kg. How long does your Mollie keep it altitude before going down (without alt-hold), Copterrichie?

[copterrichie]

Well, I can not do a hands off if that is what you are asking, the throttle requires continuous adjustments of a few clicks/points due to changes in the wind speeds crossing over and under the props.

[vpb]

Hi man, I mean when the wind is calm, you just take off, and when the copter reaches its altitude, you stop increasing throttle right? So how long can you do throttle-hand-off? And later then your copter's behavior will go up or fall down?

[copterrichie]

My point is, I never do a hands off. Just not my flying style.

[vpb]

Oh richie, I didnot mean hand-off. I meant when you take off, there'll be a stop-point for throttle, just about some seconds before you do your flight.
For my reason, I want to know some other copter behaviors, whether it gains or looses altitude, and how long before it gains/loose (1,2 or 3 secs)?

Btw thanks for your reply!

[copterrichie]

You may have seen this video before, but this is exactly how all my copters are tuned. I personally use this as a standard being, how well the copter will maintain altitude with nothing more than throttle control.

http://www.youtube.com/watch?v=GHoeGdqhdtU

[cih79]

Hello guys.
I think this topic is right for my problem. First of all, let me just say that I had some good experiences in the past with MultiWii 2.1, a handmade controller and simple aluminum frame. I have 2 videos that show that the flying experience was smooth:
http://www.youtube.com/watch?v=6BxaBB8mHSk
http://www.youtube.com/watch?v=_VuunoTG71s
Now I am trying to experiment with Turnigy Talon and MultiwiiPro from HK, and the results are not that great. The feeling is that the quad bounces up and down: I begin to push the throttle a bit and suddenly the quad takes of accelerating. When cutting just a bit on the throttle, the quad begins to stall and I need to give him a new push. These things didn’t happen in the past…the difference between the quads that I had and the new one is not in the weight (approx. 1.8 kg both). The difference it’s in the controller type and construction material…so that’s why I am a bit puzzled.
My settings are attached.
Can you give me some hints on what should I do next to be able to take a breath and not constantly move the throttle stick?
I also tried using mid point 60 and 70, throttle expo to 2 (actually the behavior was worst), I tried to play a bit with expo rate 30-50-70.
Thank you.
Cris

[Maarten112]

I have the same issue with my rctimer 450 quad, simonk flashed escs and rctimer 2830 motors.

I noticed that some throttle expo made everything better (Thr Expo 0.3), but the quad still is very bouncy and wants to climb. On my tricopter (HK KK 2.1: without the lcd, only gyro's) I can almost do a hands off hover without any problem and without the tri to climb or "fall". Anybody who can tell me what to do?

[Electro 2]

Wow, I find some of these answers odd as I have ended up in a totally different set-up. In reality there is no "down-throttle", Mother Nature supplies the down part, it's gravity, and it's always there. Logically we want to spread the amount of usable "up" across a wide range of stick throw angle for ease of control. The down portion is throttle-below-hover and probably needs to be small as you won't be there often. Result: I set the mid-point at 10-15%. As the stick is moved up, the motors rise from the MINTHROTTLE value to the hover range very quickly and the rest of the stick throw (80%) is *very fine* graduations in hover and climb. Seems to work a treat for me. Slick smooth hover with reasonably controlled descent.

[jerbs]

I also have the multiwii pro w/mtk GPS from hobbyking and this is the 1st time I have ever came even close to getting a multiwii to be stable. I have built quite a few quads using the naza FC and have flown so smooth that a young child could fly it w/o every flying anything before..

The Multiwii not so much, yes I know:
#1) you get what you pay
#2) you need to know your way around the Arduino
#3) lots of tuning

Those are the 3 most common answers I get when I ask for help. I've actually been building things with Arduino (mostly small autonomous robots), and yes the Naza is insanely easy to setup. My question is why is it that DJI can release a FC so extremley stable out of the box, yet you can't buy or build a Multiwii FC to be anywhere near as stable w/o a lot of work. I know that "all frames and motor/esc combos are different and require different setups", but I've built extremely different size quad/hex copters w/the Naza and rarely had to adjust anything at all.

It seems like the Multiwii would be close to the same if you are using the same type of sensors (which I always have (gyro, acc, barometer, mag, gps)); but like I said I almost have one stable for the 1st time, I'm pretty excited about it too. I want to do FPV w/it and I'm not a great pilot, in fact I haven't flown anything in 6 months because I got so tired of working on them and never flying them.

I think I have my pitch/roll "P" values at 4.5, yaw at 8.5, I left the default "I" values for pitch/roll/yaw, and 19 for all "D" values on pitch/roll.
My MID throttle is at .50 and expo is set for .65
My Roll/Pitch Rate .90 and Expo at .81

Can anyone offer any suggestions for a more stable flight or see anything wrong with my values stated above? I would really appreciate it.

Thanks

[copterrichie]

When an entity controls both hardware and software (Example: Apple Computer), that becomes a very easy task. Look at the variance of the Flight Controllers and the uniqueness designs of each build, I believe you will see, it is not an issue of getting what one pays for but a accomplishment of Freedom of expression.

[Electro 2]

Jerbs: I agree and had just about reached the same conclusion, I suspect my next bird will have a Woo Kong in it, not MW. As far as the PID tuning goes, it would help a bunch to know the type of instability you experience, size of the bird, all up weight, and maybe props. Then we can compare notes with other flyers settings and make an some sort of educated guess.

[scrat]

I have the same issue with my rctimer 450 quad, simonk flashed escs and rctimer 2830 motors.

I noticed that some throttle expo made everything better (Thr Expo 0.3), but the quad still is very bouncy and wants to climb. On my tricopter (HK KK 2.1: without the lcd, only gyro's) I can almost do a hands off hover without any problem and without the tri to climb or "fall". Anybody who can tell me what to do?

Set LPF filter at 42Hz for gyros and your quad will not be so bouncy.