ESC RPM check not allowing takeoff

Hello all,

I’ve been working through the guide How to methodically tune (almost) any multicopter using ArduCopter 4.4.x

I have a 32 bit esc, and bdshot running on 6 motors. I get esc rpm back as I can see it on the status page of mission planner with USB connected and motors spinning. I thought the TKOFF_RPM_MIN was a cool feature, as I have had a copter flip over because of a bad motor before. But I cannot get it to work.

Despite being able to see the rpm already, having rpm1_type selected to esc telemetry, having the bitmask of rpm1 set to my motors (channels 9-14), and trying various related params my takeoff is still being blocked, even down to checking between 10-100 RPM as my minimum. My rpm without props is reading at 1600 after arming.

It makes me worried about my harmonic notch filter as well. Is it not getting rpm data? (It’s possible that I’m also just bad at tuning.)

Thanks again guys.

4.5.0-beta2 so I can have bdshot on 6 channels

Post a zip file with your intermediate.param files and a .bin log file with the takeoff attempt

rpm1_type does not work with this feature - you need to be using ESC telemetry, either via CAN or via BLHeli/bdshot

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I’m working on getting you the .bin. Having to do an indoor test without props due to weather today.

@andyp1per my ESC telemetry is bdshot. If I am interested in using the tkoff_rpm_min, how can I pass the rpm data from my bdshot over to the rpm this feature is referencing?

It should happen automatically - do you have ESC telemetry in Mission Planner for all your motors (i.e. do a motor test and check that escx_rpm gives you data?)

Please post your params

params.param (19.8 KB)

I’ve had to adjust some arming and logging settings for my indoor props-off situation today. I get escx rpm data on the status page, but only over a USB connection. Over telemetry radio there is no data (despite having the SRx options selected).

bin file: Bin files - Google Drive

Config looks correct. Which flight controller?

Telemetry may be because you need to use Mavlink 2 to get ESC data

Note there was a bug related to this in 4.4, but it should be resolved in 4.5

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Pixhawk 6C (full size). Using 4.5.0-beta2 so I can have 6 bdshot channels

Ok, I only ever tested this with 4 - let me see if I can reproduce

Note that Pixhawk 6C has had bdshot on 8 FMU channels for a while - its only the IOMCU channels are are changed in 4.5, but you are not using those.

Oh, I was told by someone else here to use the beta firmware. I had attempted it on 4.4 and could only seem to get 4 channels back, but I might have tested wrong.
Seems I may need the beta firmware anyway to get this takeoff check to work though!

Should I be worried about harmonic notch not receiving ESC RPM?

Yes, you should be worried.

I did not mean any offense, I just didn’t understand the terminology. Here are my intermediate param files. Params - Google Drive
I have only worked up to 17 thus far, as I’ve been having issues with this harmonic notch filter.

I have compared the params on every file you have kindly provided me up through 17_notch_filter_results. So far, all I’ve discovered that’s different is some harmonic notch frequency changes. Which I greatly appreciate, as I am not good at tuning yet.

May I ask what other things I have missed? I’m genuinely trying to learn.

To clarify, I can see the ESC RPM while connected via USB. But my discussion with @andyp1per leads me to believe that if the tkoff_rpm_min cannot see my bdshot RPM, then neither can the harmonic notch.

I will attempt to revert to 4.4.4 with the same params and see if I still have 6 channels reporting back bdshot RPM on the FMU. But if harmonic notch isn’t actually utilizing the live RPM data, I may be in trouble.

They should not be related. The takeoff issue is a bug that I have just replicated. The harmonic notch should have no issues.

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My apologies, poor assumption on my part. Thank you for your help!

I reverted back to 4.4.4, and as you have told me, bdshot does in fact work on 6 channels. The tkoff_rpm_min setting seemed to work as well!

What improvements have been made in 4.5.0-beta2 that could help performance with my Pixhawk 6C hexacopter? Or do you recommend staying with 4.4.4 for the meantime?

I was able to find it on Github’s release notes. The extra EKF variance filter seemed to be helping, as I used to see lane changes frequently and with the beta firmware I saw fewer. Please do let me know if you or someone is able to patch the beta firmware, I’d love to utilize it!

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You have the intermediate parameter files I provided, I advise you to reset to default parameters with 4.4.4 and do the configuration from scratch. You now have done some changes that are not necessary (RPM_* and other stuff) and those will go away by doing this.

With the intermediate .param files it is very easy to redo the entire process. And post the annotated .param files with your comments on why you changed each parameter.

Once the bug is fixed in 4.5.0 you can update the FW without having to re-do the configuration.

Found it:

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peterscache12_3.zip (220.3 KB) notice the new file 40

The fix is in 4.5beta3 which has just been released - so if you could try that and verify I would be grateful. This might also explain your notch problems.