Takeoff blocked: Waiting for ESC RPM

vibranium · February 16, 2024, 5:28am

Dear Community,

I am trying to use TKOFF_RPM_MIN functionality to avoid topple during takeoff. If the motors aren’t spinning at this RPM then the vehicle should not try to takeoff.

Issue description: “Even though the motor rpm average is above the takeoff min rpm, the take off is still getting blocked”.

Hardware Setup

ESC Telemetry-BLHeli_32 compatible connected on AUX-1, AUX-2, AUX-3, AUX-4
Cube Orange
Mission Planner

Firmware Parameter

ArduCopter 4.3.6
RPM1_TYPE = 5
RPM1_ESC_MASK = 15 (Channel1, Channel2, Channel3, Channel4)
TKOFF_RPM_MIN = 100
MOT_SPIN_ARM = 0.02
I am receiving ESC telemetry data (rpm, voltage, temperature), so no need to mention those parameters.

What is working.

Getting esc1_rpm, esc2_rpm, esc3_rpm, esc4_rpm
Getting rpm1
esc1_rpm, esc2_rpm, esc3_rpm, esc4_rpm and “rpm1” on ARM is around 275

What is not working.

After ARM, “Takeoff blocked: Waiting for ESC RPM” message keeps on coming.
Increasing throttle does not allow UAV takeoff.

I have followed below documentation for setup and testing.
https://ardupilot.org/copter/docs/tkoff-rpm-min.html

Below document shows this feature does work on SITL.

github.com/ArduPilot/ardupilot

Copter: takeoff check that motors are spinning at TKOFF_RPM_MIN

ArduPilot:master ← rmackay9:motor-block

opened 11:16AM - 19 Jul 22 UTC

rmackay9

+163 -4

This is an alternative implementation of PR https://github.com/ArduPilot/ardupil…ot/pull/20856 This adds a Copter takeoff check that all motors are spinning at at least TKOFF_RPM_MIN. If the motors aren't spinning at this RPM then the vehicle is unable to takeoff and a message like, "Takeoff blocked: ESC RPM too low" appears until the motors do spin-up. - AP_ESC_Telem gets new is_telemetry_active() and are_motors_running() methods - AP_Motors gets new get/set_spoolup_block() methods to allow an external caller to stop the motors from spooling up to THROTTLE_UNLIMITED. This is done by ignoring calls to get_desired_spool_state(THROTTLE_UNLIMITED) if the block is true. This should be safe because it essentially only blocks the motors from spooling up if they haven't spooled up already. Even if the block is set while the vehicle is armed and flying, it won't immediately cause the motors to spool down. - Copter::takeoff_check is added to set the motors block if the vehicle is armed and landed AND ESC telemetry is inactive or the RPM is below TKOFF_RPM_MIN - Stabilize and Acro are modified to send zero throttle to the attitude control until the spool state has created unlimited This feature cannot be used if MOT_SPIN_ARMED = 0 (maybe we should add a pre-arm check for this) Once proven to be safe this feature could potentially be extended to cover other checks we wish to run post-arming but pre-takeoff (who knows what those might be though). To-Do: - [ ] Test all modes for both multicopter and helicopter to confirm it really does keep the vehicle on the ground. - [x] Test on a real vehicle This has been lightly tested in SITL including the following test: - start sim_vehicle as a copter or helicopter - stabilize (or whichever mode you would like to test) - param set DISARM_DELAY 0 (to give you enough time to play around without the vehicle automatically disarming) - param set TKOFF_RPM_MIN 1100 - arm throttle - rc 3 2000 <-- the vehicle should fail to takeoff and an error message should be displayed because TKOFF_RPM_MIN > SIM_ESC_ARM_RPM - param set TKOFF_RPM_MIN 1000 <-- the vehicle should takeoff

Please let me know if I am missing any parameters.
@rmackay9
@andyp1per

xfacta · February 16, 2024, 6:18am

I must admit I’ve not used this parameter before but it looks highly useful.
Looking through the code it might only need the ESC RPM data and doesnt appear to check RPM sensor if you have ESCs that provide RPM. I could be wrong, but let’s forge ahead regardless

So try disabling the RPM sensor and see what happens.

It also depends on the ESC/Servo output mask - which most people set when they dont need to.
Usually this is all you need for BLHELI ESCs, (plus a few other parameters unrelated to this discussion)

SERVO_BLH_AUTO,1
SERVO_BLH_MASK,0

You dont need any value in the MASK unless you’ve got special BLHELI devices apart from your main motors. So if you have something in that MASK that shouldnt be there, that will cause the minimum RPM test to fail too.

andyp1per · February 16, 2024, 8:05am

Right it relies on the ESC library. Given that Helis can use the RPM library we should probably try and fix that.

vibranium · February 16, 2024, 11:23am

Thanks for the reply.

I did try the suggested settings.

Test Case:
Disabled RPM1_TYPE and RPM2_TYPE.
image (4)
image (3)

SERVO_BLH Params

SERVO_DSHOT Params
image (6)

TKOFF Params
image (7)

Result:
Result is still same.
image (2)

Please let me know if anything left.

vibranium · February 16, 2024, 11:28am

Thanks @andyp1per.

Do you mean? This feature is broken for Multirotor and does require fix.

I have further doubt whether this feature is only applicable to Bidirectional DShot ESCs? Or If Normal DShot ESC with ESC Telem feature should work?

andyp1per · February 16, 2024, 11:30am

It works fine with multi-rotor but only if you are using ESC telemetry

vibranium · February 16, 2024, 11:49am

Thanks.

I have Setup ESC Telemetry and I am able to receive ESC telemetry data (rpm, temperature, voltage) but when I do set TKOFF_MIN_RPM to any value except 0 it keeps on giving Takeoff blocked: waiting for ESC RPM.
Can you have a look on above parameters and let me know if I have missed any parameters, please?

andyp1per · February 16, 2024, 11:52am

Seems like it should be working. Do you have telemetry for all your ESCs? Each motor is checked individually. Try increasing TRATE to 50, say and see if that helps.

vibranium · February 16, 2024, 11:55am

I have “T-Motor F45A V2 3-6S BLHeli_32 4-in-1 ESC”.

andyp1per · February 16, 2024, 12:05pm

Should be fine. It’s similar to the ESCs I use.

Can you post a log?

vibranium · February 16, 2024, 1:25pm

Thanks for continuous support @andyp1per. Please find the attached log below.

98 01-01-1980 05-30-00.zip (669.0 KB)

vibranium · February 19, 2024, 4:06pm

Hi @andyp1per,

I was hoping if you could have a look in the log and let me know if something is left to setup.
It would be really helpful in solving the my current toppling issue of drones. Thanks in advance.

andyp1per · February 19, 2024, 5:55pm

Ah - this is a bug that was fixed in 4.4 with flight controllers that use iomcu. It won’t work on 4.3

vibranium · February 21, 2024, 6:39am

Thanks. I will try out in 4.4 then.

vibranium · April 12, 2024, 7:00am

Dear Developers,

I’ve conducted tests in ArduCopter 4.4.4, and the results are positive. The UAV remains grounded until the TKOFF_RPM_MIN threshold is reached. Additionally, I performed another experiment by securing one of the propellers on an arm and attempting takeoff. Despite the tied propeller motor RPM reaching large values like 10,000 or 20,000, the UAV did not lift off. In summary, the feature functions as expected. Thank you once again for your support!