ATC_RAT_PIT_D,0
ATC_RAT_PIT_FILT,20
ATC_RAT_PIT_I,0.2
ATC_RAT_PIT_ILMI,0
ATC_RAT_PIT_IMAX,0.4
ATC_RAT_PIT_P,0.027
ATC_RAT_PIT_VFF,0.1
ATC_RAT_RLL_D,0
ATC_RAT_RLL_FILT,20
ATC_RAT_RLL_I,0.2
ATC_RAT_RLL_ILMI,0
ATC_RAT_RLL_IMAX,0.4
ATC_RAT_RLL_P,0.027
ATC_RAT_RLL_VFF,0.06
Yep. Looks really good for a starting point. You should get no rapid oscillation at all with those settings. You can use either Channel 6 tuning to try raising either pitch or roll one at a time in flight. Or land and change it manually and retry. If it flies fine at .027, then raise it to .037, and so on, until you get instability. Hopefully you get up to at least .1 where youâll get really good Loiter performance, and then will need less feedforward (VFF).
You only need to take off and hover at no more than 1/2 meter off the ground to test it. As if the heli gets unstable you can just land right away to adjust it. It will be better to find an instability there than at 2-3 meters off the ground.
If you get oscillations and instability with those numbers you need to look at your mechanical setup.
Getting to .2 on P gain would be really good, but not all mechanical setups and servos are going to make it that far. And your setup likely wonât. Looking at these values:
H_COL_MAX,1480
H_COL_MID,1360
H_COL_MIN,1230
you only have 1480-1360=120 servo travel from zero collective to maximum, which means your swash plate is moving really fast with very little servo travel. So you have a pretty high rate built into your mechanical setup. That will not let you adjust the P gains up much, and is going to require very fast and accurate servos. That is a very good setup for 3D flight where you would likely run 14 degrees of collective pitch. But for UAV going to 10 degrees of collective, I think it should be around 190-200, unless you have very slow servos.
For the autopilot to fly the helicopter is the same as for you. If you make very fast stick inputs with a properly set up heli, what happens? If you make more gentle stick inputs flying that same heli - slower and smoother - what kind of flight characteristics do you get? That is what the rate PIDâs do. The more you turn them up, the faster the control inputs to the swashplate, and how responsive the heli will become. You donât want it super sluggish or it wonât fly good. If you make it too responsive, it can cause it become unstable. It needs to be responsive enough for it to fly good in Loiter, and for you as the pilot to fly it in Stabilize or Alt Hold. But not so responsive that it becomes unstable.
Every pilot has a different preference on how the heli should âfeelâ. So itâs really hard to say set it to âxâ and itâs going to work. It is no different than setting up expo and rate in your radio to fly without Pixhawk. Itâs how YOU want it to feel and fly. And once you get that, then test it in Loiter. If itâs âdriftyâ and doesnât hold position well, then you need to tune it sharper until it performs good in Loiter.
Geoff, Iâm a little concerned about your description of the behavior of the swashplate:
I made a short video for you to demonstrate the correct behavior, or how it should work on the bench, in Stabilize flight mode with the pixhawk unarmed.