I've got a little problem with my quadricopter in minimum throttle; My config is : Frame QAV 250/FC CRIUS V2 AIOP/Motor: Multistars Babybeast 2300kv/ Soft : Multiwii 2.4/GUI:Multconf. The weight of my quadri is less than 450 gramm. So my problem is the stabilization of my quadri when the throttle stick is low. Even if i increase the minimum throttle in the GUI, the quadri is not stabilize when is going down and my throttle stick is in the minimum position. I had tried to find a solution on the forum but i don't find it. I find on google the solution to trim after the quadri is takeoff but i this solution is not good for me.
Regards. PS: Sorry for my english level... I'm french.
VinZ974 wrote: So my problem is the stabilization of my quadri when the throttle stick is low. Even if i increase the minimum throttle in the GUI, the quadri is not stabilize when is going down and my throttle stick is in the minimum position.
This can normally easily be fixed by simple PID tuning. When the quad oscillates (acts unstable) during descent one or all of your PID settings are not quite right for stable descent. If you are using the default PID values in roll and pitch you may need to change one or both. In a well balanced quad you want to have both roll and pitch the same as each other but if the defaults make the quad unstable you really need to change them. If the quad is badly balanced the PID for roll and pitch could be different from each other and still make it work better. To cover your next question before you ask it, try increasing the values a little at a time until you notice either some improvement when descending, or if it gets worse, try decreasing.
Thank you so much for your answer Kbec5709. My quad don't oscillate during hoovering, crusing, , when i up or down slowly. It happen when my throttle stick is in low position. When i try to have a fast descend the quad flip. it's like the gyro don't working when my throttle stick is low but the motors are turning. If i increase the throttle the quad back stable. My PID are little bit modify than the original. I will try your idea. I will keep you updated. but if you have got an other idea...
Yes, these are still symptoms of PID tuning. If your Gyro was bad it wouldn't hover or fly at all. The fact that it flips on quick descent is one of the signs that at least one of the PID settings are wrong. PID tuning can be a bitch but once you get things right you will know. Other things that I would check (although the probability of it being something else is really low) would be ESC timing (they can be set slow, fast, medium) or even braking (some ESCs have a brake setting that if used can cause issues,) ESC calibration (should be ok since your craft hovers,) or craft C.O.G. If that is off it could theoretically cause balance problems at really low RPM (but you would have to have something like a battery hanging over the side for that to happen.)
Last edited by Kbev5709 on Thu Oct 29, 2015 1:06 am, edited 1 time in total.
Even if i increase the minimum throttle in the GUI, the quadri is not stabilize when is going down and my throttle stick is in the minimum position.
try the opposite: lower min throttle to the value, where the motors just start turning. If min throttle is to high, the controller has no room to stabilize the quad on fast descents.
Even if i increase the minimum throttle in the GUI, the quadri is not stabilize when is going down and my throttle stick is in the minimum position.
try the opposite: lower min throttle to the value, where the motors just start turning. If min throttle is to high, the controller has no room to stabilize the quad on fast descents.
He has a valid point as well. Why the need for fast descent? Racing? (Just wondering)
Thank you "schnupperm" & "Kbev5709". Yes I want to try to do "FPV racing"; I writing "try" because it's very difficult for me to have a stable height with the goggle in my nose. If i see the quad in 'visual' (without goggles ), there is no problem to me to have a stable altitude. I think, i'm so abrupt with the throttle stick when i'm in FPV, and that's why i have had many crash because in don't know the position of the stick in my telecommand. I will try to change the PID of the roll this week-end.
FPV (slow flying or racing) absolutely requires perfectly tuned PID's. Here's a little test I like to do to test how close my PID's are...
1. Bring the copter to a stable hover just high enough to be out of ground effect (1m or so) 2. Punch it but apply NO rudder, pitch or roll, allow it to climb 30m or so. 3. Cut throttle to where it's descending quickly but is still stable (maybe 25-35% throttle) 4. Arrest the fall so it stops and is hovering back at the original height.
If it goes straight up and back down its pretty well tuned, if it moves more than a meter it two out of position horizontally it's not tuned that well.
So this week-end, i have tried to set-up my PID. Before this week-end i had the "stock" PID (Roll /P:3.3 /I:0.030/D:23 Pitch P:3.3 I:0.030D/ Yaw Etc....) Now , My Pid's are : Roll P:6.8/I:0.026/D:23 /Pitch: P:7/I:0.029 D: 23 The others parameters are "stock". So the problem is the same. When my quad is going down with the minimum stick of my RC is in the minimum, the quad is doing back and when i push the throttle stick in 35%, he stopping to flip and come back stable... And now my quad have more altitude variation without touch the stick throttle....
Cereal Killer: With "Stock'' PID, When i do your test with the throttle stick at 20%, the quad is going down and do not flip;
Last evening, i did other tests. I start the GUI and connect my quad, and i have realised when i arm my quad there is no stabilisation when i was in minimum throttle. If i move the quad, i can see in multiconf the motor's remain in the same speed, but if i increase a little bit the throttle stick, the motor's try to stabilize the quad... Is it the same for all user of MULTIWII?
