Problems with AutoTune on Matek F405

Hi All,

Thank you in advance for your assistance. I am building my first, Hexa and I am struggling with getting it to work with anything else but Acro and Stabilize mode. As soon as I switch it in auto-tune, it struggles to maintain altitude resulting in going higher and higher. Please see my log file

Thanks for your help
Valentin Danev

Did you follow these guidelines first before attempting AutoTune?

Hi Dave,

At first i did not and the flight was horrible. Than i followed the guide in mind and set it up for 10 inch props. Now it feels a lot better in Acro and Stabilized mode. But as explained above it goes crazy if i select auto tune.

A bit premature to try auto tune. Does it fly and hover in Altitude Hold? Loiter?

I have not tested that. But i can test that and post the logs if this is going to help.

Yes, do that. Hover in Altitude Hold for a minute and post the .bin log.

Thanks for your help i will do it tomorrow.

Hi Dave,

I did as advised. read the post again and made sure it is all set up for 10 inch props. And tested in stabilised and alt hold as you have advised. It was a bit better and did not take off this time but it was struggling to keep altitude all the time. the log is available on ( I have noticed the baro alt / gps alt and ctun alt does not match for some reason. I hope you can help.

Your Z vibration levels are high, this will cause altitude instability. You got the MOT_BAT_VOLT_MAX and MIN wrong. It’s 4.2x Number of battery cells and 3.3x Number of Battery cells for these parameters. So, it looks like you have 4S then 16.8 and 13.2 is what you want. Balance the props, use better isolation to mount the FC and correct the Motor voltage scaling and try again. Do you have a piece of foam covering the barometer? It’s required.

Hi Dave,

Thank you so much for your fast response. This is my first dive in the ardupilot community and i am extremity impressed by how helpful people like you are. Thanks a lot. I will try today.

From the log I don’t see it struggling to keep altitude as you describe. At mid throttle the motors are ~1500pwm which is what you want. It wasn’t in Alt Hold long enough to learn the MOT_THST_HOVER value but everything else in this regard looks OK. What do you mean by “struggling”?

OK I do see the motors cycling when it was in AltHold. It could be from the high vibration levels. I’m not sure what the Motor voltage scaling being so low would do.