Hello,
I am using the VESC for onboard energy regeneration for a tethered drone (https://www.skypull.technology/). Right now I am testing regeneration on a bench test, using 2 connected motors, one acting as the driver and the other as the generator.
I encountered a strange phenomenon : if I set the duty cycle of the first motor (driver), both motors have a given erpm. But if I brake with the 2nd motor the erpm increase and the VESC is even telling me I generate energy ! It works for low braking current, if I increase the braking current too much the erpm decrease.
Here is a video of a test: https://youtu.be/TgVPkXjpWeEthat. In this case with no brake the eRPM of the system is 27200. I input a brake current of 1A for the 2nd motor (generator), the erpm increase to around 30000. And the VESC measures an energy production around 6.5W.
The regenerative motor is in FOC mode, it is a scorpion SII 4025 520kV. VESC is version 4.12, with latest firmware. Idem for VESC tool.
I noticed the same phenomenon in rpm control, for example in a test I set the first motor to rotate at 15000erpm and I increased the rpm of the 2nd motor in VESC tool. Until 20 000erpm I generated energy.
Does anyone have any idea of what is happening ? Am I missing something ?
Thanks in advance !
Olivier
1A is very low compared to the full range (about 0.3 %), and motors with low inductance tend to cause offsets on those low currents, which is why the offset probably is big enough to even flip the sign. This is much less of a problem on the VESC 6 plus due to the configurable current filters on the hardware.
Thank you very much for your reply.
This brings me another question which is how can I find the precision of the current measurement of the VESC ? I tried looking at the BOM, but I could not figure out this information.
Indeed I am interested in measuring precisely the power consumed/produced with the VESC.