FOC parameters measurement problem.

Discussions regarding the Field Oriented Control (FOC) implementation on the VESC.
ThierryGTLTS
Posts: 86
Joined: 09 Aug 2017, 11:10

FOC parameters measurement problem.

Postby ThierryGTLTS » 16 Aug 2017, 10:45

Hi to all,

At last I've succeed to make my U8 motor spin in BLDC mode after a lot of (solved) problems.

But when I wanna measure the motor parameters for FOC, the test seems to require a very large current topping my 2A PSU current limit.

Do you know what is the minimum current required to obtain good parameters :?: :!:

According to manufacturer, R = 0.186 ohm ph to ph, and I measure a lower value.

Have a Nice Day.

Thierry

rew
Posts: 939
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: FOC parameters measurement problem.

Postby rew » 17 Aug 2017, 05:08

1) put the powersupply in 1A current limit mode. Try to be accurate. Consider checking the powersupply by connecting the multimeter across the leads in 20A mode (2A if you have it).
2) connect the powersupply to the motor leads.
3) Use the multimeter in 200mV position to measure the voltage across the leads you've used. (measure at the leads of the motor, not at the leads of the powersupply or even worse, at the powersupply side of the powersupply-leads).

The number in mV is the resistance in mOhms of your motor.

For use in VESC, that number needs to be halved: Benjamin assumes a Y-wound motor, and wants to know the winding resistance of a single winding. In case of a Y wound motor, you'd be measuring 2 windings in series like this. (in reality the winding resistance is 3x more and your motor is delta-wound, but that doesn't matter.).

ThierryGTLTS
Posts: 86
Joined: 09 Aug 2017, 11:10

Re: FOC parameters measurement problem.

Postby ThierryGTLTS » 17 Aug 2017, 08:28

Thank you.


I have measured resistance and inductance with a good LCR meter at 1 and 10 kHz.

10kHz values are more appropriate in this case.

Resistance is about same as TMotor announce (0.186mR) on it's website, good :!:

Inductance vary slightly with rotor position, I've found between 102 and 128 µH Ph to Ph, so about 57 µH for each winding.


Do you know where I can found explanation of the numerous constants and terms used by Benjamin in BLDC TOOL :?:

I know a lot of them, but some are unknown for me especially in the FOC and Advanced Tabs.


Thanks for your help.

Thierry

rew
Posts: 939
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: FOC parameters measurement problem.

Postby rew » 17 Aug 2017, 18:51

Do you know where I can found explanation of the numerous constants and terms used by Benjamin in BLDC TOOL 
Same here.... :-)

slapshot136
Posts: 27
Joined: 15 Sep 2016, 18:24

Re: FOC parameters measurement problem.

Postby slapshot136 » 27 Aug 2017, 13:45

I am also curious exactly what they are, especially the "D current injection" duty and factor


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