According to the FOC theory, the phase current should be directly measured from the stator. However, the schematic of DRV8301-HC-C2-KIT shows the current shunt resistors are at the low side of each half bridge. The method should be equivalent to direct phase current measurement. How can I understand it? Thanks
I have attached a document for the FOC algorithm that we include in kits like the DRV8312.
5611.Sensorless FOC of PMSM.pdf
Motor Drive Application Manager
I think I have read it before. It's basically the same as the doc in DRV8301 kit.
I don't understand why the FOC algorithm requires coil current but it actually measured the lower leg current. In single shunt reconstruction, the current measurement is done at specific PWM times. Thus, I read some code the FOC sensorless sample project in controlsuite, C:\TI\controlSUITE\development_kits\DRV830x-HC-C2-KIT_v100\PM_Sensorless\, it seems that the ADC is triggered by PWM1 SOCA when the counter is down to zero. However, the it also means there is no power to the coils during current measurement. Is it reasonable or totally ridiculous? Or, do you have any other docs?
This may help. The bottom most waveform (ADCresult4) is how the total phase current responds.
Thanks for the nice drawing.
Latter on, I read the FOC control code coming with drv8301 kit. It actually triggered the ADC conversion at PWM time-base counter to 0. Thus, the upper arm of a half bridge is off, and the lower arm is open,which is not quiet consistent with the drawing you posted above. Probably, its still depend on the PWM configurations and the actual HW configurations.
I was wondering where you got the schematic for the DRV8301-HC-C2 Development Kit.
Everything included gerbers, code, documents, etc. is in ControlSUITE.
To save you the hassle, I have also attached the schematic to this post. RevC and RevD are attached.
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