Airmode not keeping quad stable for flips/rolls w/throttle low

ArduCopter Copter 4.0
81

May I jump in here too.
I did some testing with MIX_MIN today in ACRO and experienced the same thing (I went up to MIX_MIN: 1.3). If I push throttle to min the quad is stable for a few seconds and than loses its stability like with MIX_MIN=0.1.
From racequads I am used to be able to cut throttle completely for as long as I like and the quad stays stable in the air what ever position it has. I added also the bin file if someone would like to look into it: https://www.swisstransfer.com/d/f54acb3f-8844-4276-b43c-0e8ae6e2f5a2(see pic).

MIX_MIN
MIX_MIN1836×927 202 KB

Questions:
I do not understand the answer from Leonardhall: Not exactly. The value being used slides to MIX_MIN over a second or so when:

  • Does that mean after a few seconds with min throttle and the quad being for example upside down control is lost?
  • What is your suggestion for my quad; should I continue to ramp MIX_MIN from 1.3 up further?
  • Is having higher MOT_SPIN_MIN values helping MIX_MIN since the min rotation speed of the motors is higher?

Thanks a lot for your help

82

If you are in ACRO then you want to use MIX_MAN. Mine is set to 4

83

ok than I will try tomorrow to ramp it up
thanks

84

Am I correct to have ATC_THR_MIX_MIN< MOT_SPIN_ARM & MOT_SPIN_MIN?

85

As far as I know, in manual modes (the _MAN bit), MIX_MIN and MIX_MAX are not used.

86

They’re not really related. Also, the MOT_SPIN parameters are expressed as a fraction of maximum thrust (actually a fraction of configured PWM range), while the THR_MIX parameters are a fraction of hover throttle, so we can’t equate them like that anyways.

87

I made some tests.
With ATC_THR_MIX_MAN: 1.8 I had a similar feeling with throttle cut as with Kiss hardware. But once I tried a bit slow take off in ACRO the quad flipped up side down.
I than did a take off in Loiter and it flipped too.
Is MIX_MAN active in all modes?

88

It should only be active in manual modes - stabilise and acro. The flip is likely caused by stabilisation occurring while you are still in contact with the ground. This is why it’s important to take off quickly and when you come in to land better to have airmode disabled otherwise you will tend to bounce and flip. I enable airmode using ACRO_OPTIONS and that way I can land in stabilise.