Quad tumbled at low throttle settings in STABILIZE

ArduCopter Copter 4.5
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This is a new 7" build and I just finished getting through @andyp1per 's build video series (through part 21). I had previously successfully completed autotune on all axes and was going out today to test FPV and acro when I encountered some unexpected behavior.

I started out by doing some throttle punches and chops in stabilize mode (not super fast but not super slow either) and I immediately noticed that the quad appeared to become extremely unstable when I cut the throttle or had it anywhere below about 1/4 stick.

I also observed the quad appear to resist forward motion in stabilize (I tried to pitch forward with the throttles around hover throttle) and then it violently tumbled. This felt akin to being in horizon mode in betaflight where you exceed the angle that allows you to do flips/rolls. The quad fell and recovered upright just before hitting the ground but it ended up bouncing as I tried to save it.

At first I thought this had something to do with me enabling airmode for ACRO but during this brief flight, I never even transitioned into ACRO because I was so confused about what was happening. The quad never did anything like this on my handful of previous flights, though I was never pushing it much above hover throttle before.

I know I have some mag interference that I need to mitigate but it was “ok” enough for me to arm and takeoff.

Any help diagnosing the tumbling/stability issue would be greatly appreciated! I’m still a complete noob with AP/AC and I am not yet proficient at reviewing logfiles to diagnose issues.

Thanks!

Log
Params

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You can get faster throttle response in stabilize by increasing ANGLE_MAX - default is 30 degrees but I usually set to 75.

The loss of control simply looks like the fact that you need airmode. Without airmode you get no stabilization at zero throttle.

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Hi @baconwings,

I think this is that you have set ATC_THR_MIX_MAN 0.1. I would suggest 0.5 to 1 once you have finished tuning.

This gives the aircraft more control authority when you are at minimum throttle.

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4

@baconwings what both @andyp1per and @Leonardthall are recommending is part of the ArduPilot Methodic Configurator software.

If you had used the software you would not have had this problem. :slight_smile:

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5

Is there a way to enable AIRMODE for modes other than ACRO? I only saw the checkbox option to enable it under ACRO_OPTIONS… My tumbling issue happened in stabilize.

I’ll also try bumping up ANGLE_MAX as you suggested.

Thanks!

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I think arming on a switch will give you airmode, but that’s all

Also please see:

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Thank you @Leonardthall ! I’ll definitely try increasing that.

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Thanks @amilcarlucas, I didn’t even know that existed. I’m trying it out right now. By the way, I’m a big fan of your in-depth tuning guide - I used that on my Holybro X500V2.

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@Leonardthall I see there appear to be three related parameters:
ATC_THR_MIX_MAN
ATC_THR_MIX_MAX
ATC_THR_MIX_MIN

Am I correct that MAN only applies to ACRO mode (or other similar manual modes) and that MIN and MAX only apply to stabilized modes?

It sounds like MIX_MAX and MIX_MIN apply to pretty much every flight mode but ACRO and STABILIZE and MIX_MAN covers that one?

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10

I currently have my RC5_OPTION set to 154, arm/disarm with airmode. Does this enforce airmode automatically for all modes including stabilized/navigation modes?

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Only for manual modes but should include Stabilize

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