Custom hardware, VESC firmware

Discuss hardware related to the VESC such as the NRF nunchuk.
sjacek
Posts: 4
Joined: 19 Apr 2016, 13:38

Custom hardware, VESC firmware

Postby sjacek » 26 Sep 2016, 12:50

Hi guys,

I've made custom hardware for ESC and I'd like to use VESC firmware with FOC and everything.

Main differences between orginal VESC and mine:
- ACS711KEXLT-31AB-T Hall sensors for current measurements
- hardware 3rd order Sallen-Key Low-pass Filter (Butterworth type), 20kHz cut-off freq
- DRV8303

My problems:
- it works only in FOC mode
- current and voltage waveforms on phases looks wrong
- motor is getting hot
- it doesn't work in BLDC mode (param detection failed)

Some screenshots:
At start:
Image
Image
Image
Running (strange peaks):
Image
Image

Could someone look at this pictures and get me on the right track? Some suggestions, anything?

rew
Posts: 937
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Custom hardware, VESC firmware

Postby rew » 26 Sep 2016, 21:11

Possibly you have a current measurement on the wrong phase. Or maybe the sign of one of the current measurements.

sjacek
Posts: 4
Joined: 19 Apr 2016, 13:38

Re: Custom hardware, VESC firmware

Postby sjacek » 27 Sep 2016, 09:24

I checked static current and voltage measurements. They are ok.
What do you think about my filter? Maybe cut-off freq is too low?

rew
Posts: 937
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Custom hardware, VESC firmware

Postby rew » 27 Sep 2016, 17:47

Oh.. .Yeah. that might be too low.

Suppose your motor is running at say 60k eRPM (almost 10k real RPM on my 7-pole motor).

Then you're doing 1000 revolutions per second. So the phase currents are doing only 1kHZ. 20kHz is plenty!

.... except.... the current is normally measured only during the on-time of the low-side FETs. So the measured value will normally go from 0 (when the high side fet is on) to the wanted value about 40k times per second.... But if you have ACS sensors mounted in the phases, then that shouldn't be an issue, so 20kHz, should indeed be plenty.

sjacek
Posts: 4
Joined: 19 Apr 2016, 13:38

Re: Custom hardware, VESC firmware

Postby sjacek » 28 Sep 2016, 09:30

ACS are on phases.
Are there any crucial parameters dependent on hardware (dead time etc...) which I can missed?

Some times I get DRV fault, but when I check Status Register 1 there's always 0.


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