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Pitting VESC Six EDU against a Castle Creations ESC - the Castle is winning?

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jschall
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Pitting VESC Six EDU against a Castle Creations ESC - the Castle is winning?

I am evaluating VESC using a VESC Six EDU. The application is propulsion for a solar powered fixed-wing UAV, so efficiency is the primary metric on which I am evaluating VESC.

The motor is a Scorpion S-5028-220kv. When VESC performs parameter identification on the motor, it reports: R=12.5mOhm, L=18.59uH, Ld-Lq=5.62uH, lambda=3.651 mWb. On my scope it has very sinusoidal BEMF when spinning with a drill.

The motor is mounted on a thrust stand with a propeller, and I am comparing to a Castle Creations Phoenix Edge 120HV using the following methodology:

  • With the VESC connected, run the motor up to a fixed RPM (17250 eRPM). Measure the resulting thrust (~600 grams) and power input (~90-100W)
  • With the CC ESC connected, run the motor up until the thrust stand measures the same thrust (~600 grams) and measure power input (~80W)

This is a really surprising result to me, as it seems that FOC would be a more efficient commutation strategy, especially considering that this motor produces sinusoidal BEMF. I've been tweaking every setting I can find, trying to improve efficiency.

Things that have helped somewhat:

  • Increasing Zero Vector Frequency to 60kHz
  • Enabling MTPA (IQ Measured)

Things that have not helped or have harmed efficiency:

  • Tuning or detuning the current control loop
  • Tuning or detuning observer gain
  • Increasing or decreasing flux linkage
  • Changing Current Controller Decoupling from disabled
  • Changing Observer Type from mxlemming_lambda_comp
  • Changing Observer Offset from -1 to anything from -5 to 5.

Everything else I have tried has failed to improve efficiency. The Castle is still winning by a long shot. This makes no sense to me.

Things I can still try:

  • Attempt to measure losses in the ESC to determine whether the inefficiency is due to poor commutation strategy (software) or conduction or switching losses in the ESC (hardware)
  • Attempt to measure the absolute efficiency of the castle ESC and scorpion motor combination from the DC power input to the motor shaft. If this thing is already 95% efficient, I am wasting my time trying to make it better!
  • Get an encoder and measure rotor angle error and/or try sensored FOC
drummerboy5408
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This is very strange, because I use a VESC on my UAV and it performed much better than my Regular ESC.

Test #1
E-Flite ESC (BLDC) - 504g thrust @ 80.5W
Flipsky 4.20 VESC (FOC) - 502g thrust @ 75.3W

Test #2
E-Flite ESC - 503g @ 80.9W
Flipsky VESC - 503g @ 73.2W

Basically an average of 8.2% better Thrust/Watt efficiency.

I would suggest setting your VESC EDU to BLDC mode first, because if you are getting worse performance on the EDU even in BLDC mode than the Castle...then it must be something unrelated to the comparison of BLDC and FOC, because FOC should be more efficient.

 

ligi
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ligi
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jschall
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Looks like it is the EDU's fault.

VESC6 MkVI is ~22% more efficient than CC ESC.

Excited to see what I can do with some GANFETs...

drummerboy5408
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I wonder if the difference in MOSFETs between the EDU and the Mk6 would explain this