@Alex-Kushleyev

@Alex-Kushleyev said in ESC cuts out on high RPM:

@TheRealKaufmann ,

what is the RPM and current draw of the ID3 right before it cuts out at 80% (in normal operating range)?

Are you commanding 80% right away or slowly ramping up to that power?

you could run a test where you slowly ramp to 80% with --ramp-time 5.0 when using voxl-esc-spin.py command. This will take 5 seconds to ramp up to the desired power.

Hi Alex! We have tried both. It did not seem to have an effect on the outcome. Before the high current draw, everything seemed normal (I think it was 2-3A).

@Alex-Kushleyev said in ESC cuts out on high RPM:

I am going to try to replicate your setup, can you please confirm motors and props you are using @TheRealKaufmann :

https://www.getfpv.com/t-motor-f1404-2900kv-3800kv-4600kv-motor-gray-red.html (2900kV)
https://www.getfpv.com/gemfan-windancer-3028-propeller-set-of-4.html

thank you!

Alex

Yes, that would be awesome. The setup is correct. Motors are 2900 KV, GF-3028 Props and 4S Battery.

@Alex-Kushleyev said in ESC cuts out on high RPM:

@TheRealKaufmann , i just discussed with the team and we will add a new packet that will allow +/- 65K RPM control of the ESC. The change will happen in two places, the ESC firmware itself and we will also update PX4 to send out the new packet..

I believe we also need to add a check of the outgoing RPM to make sure you don't send a negative RPM by overflowing int16 (in the current packet and the new packet). This is what you experienced, if I understood correctly.

For now, it's best that you set the RPM limit in PX4 to 32700 in order to avoid reversing motors in flight . I hope to provide an update later this week.

Alex

Thank you very much, that sounds nice. Yes, I believe a sanity check for the outgoing RPM be a good thing for the exact behaviour that we have noticed. When you provide the update, we will test right away. Our new ESC has also arrived

@Alex-Kushleyev I apologise for my late answer. Thank you first of all for the quick solution! I actually modified the PX4 Firmware to give PWM commands instead of RPM, but your method seems way better. An actual fix would still be nice though

I could not test your RPM method until now. We actually had to order a new ESC (and are still waiting for it), because when spinning motor id 3 to around 80%, the ESC would cut out and currents of up to 30A were indicated in the current measurement. We tried to swap the motor, but that did not help. The weird thing is that at lower power settings (eg. 50%), the motor spins just fine. The other motor id's do not have that problem. I assume that ESC is no longer usable? Do you know what the cause could be? Temperature was always around 40 deg C.

Best regards
Tom

@Alex-Kushleyev Thank you for your thorough answer!

It would be great, if you could send us a new packet with command RPMs up to 65K.

We will check the physical RPMs again with a optical tachometer. But the battery voltage was the same across all tests.

Best regards
Tom

I noticed one more strange behaviour. I disabled the maximum RPM limit in the voxl-esc-spin.py script. When setting the RPM to 32000, everything is fine, but when setting it to 33000, the motor spins backwards. This does not happen in open loop mode.

Any help would be apprechiated @Alex-Kushleyev

Hi there,

we are using a VOXL 2 Mini along with the Mini ESC and T-Motor F1404 2900KV Motors with GF-3028-3 propellers.
After calibrating, when running the ESC with the "--power 100" flag, the RPM reports to about 35200 rpm. In the ESC config, we have set the maximum RPM to around 36000 and the max_rpm_delta to 20000 to avoid cut outs.
In PX4, we have set the maximum RPM to 35000.

But when spinning the motors to a high throttle, the ESCs begin to cut out and the motors try to restart spinning. The cut outs seem to happen around an indicated RPM of ~32000.
When setting the limit in PX4 to exactly 32000, everything works fine, except that there is a lot less thrust availabe. it almost seems as the VOXL-ESC is kind of limited to that RPM, even when changing the config file.

Our ESC Config is posted at the end of this post.

But there is also one other thing we notices (maybe it could be important):
The indicated RPM value on the VOXL-ESC does not seem to be real. For example, our motor was bench tested in our lab with a maximum value of 31300 RPM at the above configuration. Also, when comparing the thrust (in grams) at a specific RPM on the bench with the same RPM setting via ./voxl-esc-spin.py --rpm, the thrust is much lower on the VOXL-ESC than on the bench at the same indicated RPM. Therefore the RPM tracking on the VOXL-ESC seems not to be working right. I believe that our ESC configuration is right, but please double check.

Any help would be highly appreachiated since we want to finalize prototyping and start production soon.

Best regards
Tom

ESC Config for T-Motor F1404 2900KV with GF-3028-3:

<EscParameters>

  <IdParams>
    <param name="id"              value="127"/>  <!-- 0-7 .. 127 means use hardware ID pins to read ID-->
    <param name="dir"             value="2"/>    <!-- 0=fwd, 1=rev, 2=fwd id-based, 3=rev id-based -->
  </IdParams>

  <UartParams>
    <param name="protocol_version" value="2"/>          <!-- reserved for future use -->
    <param name="input_mode"       value="0"/>          <!-- reserved for future use -->
    <param name="baud_rate"        value="2000000"/>    <!-- communication bit rate -->
    <param name="char_timeout_ns"  value="0"/>          <!-- not used -->
    <param name="cmd_timeout_ns"   value="100000000"/>  <!-- timeout for incoming commands before ESC will stop the motor -->
  </UartParams>

  <TuneParams>
    <param name="pwm_frequency"       value="48000"/>  <!-- switching freqency of PWM signal going to motors. 24Khz and 48Khz are only options for now -->
    <param name="vbat_nominal_mv"     value="14800"/>  <!-- used for sanity checking and limiting of voltage-dependent funcions -->
    <param name="num_cycles_per_rev"  value="6"/>      <!-- number of pole pairs in the motor. used for converting electrical frequency to mechanical rpm -->
    <param name="min_rpm"             value="5000"/>   <!-- minimum RPM that will be attempted, otherwise capped -->
    <param name="max_rpm"             value="36000"/>  <!-- maximum RPM that will be attempted, otherwise capped -->
    <param name="min_pwm"             value="50"/>     <!-- cap for minimum power to be ever applied. max is 999 -->
    <param name="max_pwm"             value="999"/>    <!-- cap for maximum power to be ever applied. max is 999 -->
    <param name="pwm_vs_rpm_curve_a0" value="202.34228349901161"/>  <!-- this is actually motor_voltage vs rpm curve.. using legacy naming -->
    <param name="pwm_vs_rpm_curve_a1" value="0.32139836115838644"/>
    <param name="pwm_vs_rpm_curve_a2" value="3.1167552427764777e-06"/>
    <param name="kp"                  value="100"/>    <!-- RPM controller proportional gain -->
    <param name="ki"                  value="30"/>     <!-- RPM controller proportional gain -->
    <param name="max_kpe"             value="300"/>    <!-- maximum proportional erorr term (max is 999) -->
    <param name="max_kie"             value="100"/>    <!-- maximum integral error term (max is 999) -->
    <param name="max_rpm_delta"       value="20000"/>    <!-- cap for maximum rpm error used in RPM controller -->



    <param name="spinup_type"         value="1"/>      <!-- 0: traditional, 1: sinusoidal -->
    <param name="spinup_power"        value="70"/>     <!-- power used to during spin-up procedure -->
    <param name="latch_power"         value="80"/>     <!-- power used during latching stage of spin-up (out of 999)-->
    <param name="spinup_power_ramp"   value="8"/>      <!-- it will take ( 4096 / (spinup_power_ramp*10000) ) seconds to ramp sinusoidal start-up power from 0 to spinup_power -->
    <param name="spinup_rpm_target"   value="5000"/>   <!-- Desired RPM at the end of the sinusoidal spin-up procedure -->
    <param name="spinup_time_ms"      value="1000"/>   <!-- Duration of the sinusoidal spin-up procedure -->
    <param name="spinup_bemf_comp"    value="1"/>      <!-- 0: disable, 1:enable back-emf compensation in sinusoidal spin-up procedure -->
    <param name="motor_kv"            value="2900"/>   <!-- kV value of the motor. used in back-emf compensation during spin-up -->

    <param name="min_num_cross_for_closed_loop" value="100"/>  <!-- exit latching mode of fixed power after this number of zero crossings -->
    <param name="protection_stall_check_rpm" value="1000"/> <!-- if motor spins below this RPM, stall check will trigger and stop / restart the motor -->

    <param name="brake_to_stop"       value="1"/>             <!-- apply brake when stopping motor (or not) -->
    <param name="stall_timeout_ns"    value="20000000"/>      <!-- after spin-up, if no zero crossing is not detected for this amount of time, motor is considered stalled -->
    <param name="require_reset_if_stalled"      value="0"/>   <!-- require sending an array of zero commands to reset before next spin-up, if motor stalled -->

    <!--simple defualt chime-->
    <param name="tone_freqs"          value="[200, 215, 225, 250, 0,0,0,0, 0,0,0,0]"/> <!-- 200 is 2000Hz, max 255 -->
    <param name="tone_durations"      value="[10,  10,  10,  10,  0,0,0,0, 0,0,0,0]"/> <!-- duration of each tone in units of 10 milli-seconds. Poor naming!!! -->
    <param name="tone_powers"         value="[60,  60,  60,  60,  0,0,0,0, 0,0,0,0]"/> <!-- max is 255 -->

    <param name="dt_threshold_ns"       value="150000"/>      <!-- during start up, ignore inter-commutation times less than this val, probably noise -->
    <param name="max_dt_ns"             value="2500000"/>     <!-- min and max values for time between two commutations. these are used as caps -->
    <param name="min_dt_ns"             value="10000"/>
    <param name="dt_bootstrap_ns"       value="2000000"/>     <!-- filter bootstrap value for commutation dt during start up -->

    <param name="spinup_stall_dt_ns"    value="6000000"/>     <!-- during spin-up, if no zero crossing is not detected for this amount of time, motor is considered stalled -->
    <param name="spinup_stall_check_ns" value="30000000"/>    <!-- time after beginning of spinup to start checking for spinup stall -->

    <param name="timing_advance"        value="0"/>
    <param name="sense_advance"         value="0"/>

    <param name="demag_timing"          value="0"/>    <!-- unused -->

  </TuneParams>
</EscParameters>