Converting ADC Bit Value to q1.15 Current in "per Unit"?

Such conversion functions used to be part of the CMSIS DSP library, originating from ARM (and adapted by the vendor).

Not sure if and where this DSP code ended up in the current "Cube" mania.

But for the F103, you can still download "old" DSP libs and SPL-based firmware libs.

As a last resort, you could code it yourself.

Hello Daniel,

I am not sure I fully understand your question, but I will try to give you some clues.

Note that my analysis is done based on the 5.3 source code. I do not know the 2.0 version, and how far it is from the 5.3.

"I'm wondering how the software know what current is flowing through motor."

No magic here, the current is measured with an ADC. ADC voltage value is proportional to current flowing to each phases.

The currents read from the hardware are read inside PWMC_GetPhaseCurrents function called from FOC_CurrController:

inline uint16_t FOC_CurrController(uint8_t bMotor)

{

 Curr_Components Iab, Ialphabeta, Iqd;

 Volt_Components Valphabeta, Vqd;

 int16_t hElAngle;

 uint16_t hCodeError;

 hElAngle = SPD_GetElAngle(STC_GetSpeedSensor(pSTC[bMotor]));

 PWMC_GetPhaseCurrents(pwmcHandle[bMotor], &Iab);

 Ialphabeta = MCM_Clarke(Iab);

 Iqd = MCM_Park(Ialphabeta, hElAngle);

 Vqd.qV_Component1 = PI_Controller(pPIDIq[bMotor],

           (int32_t)(FOCVars[bMotor].Iqdref.qI_Component1) - Iqd.qI_Component1);

 Vqd.qV_Component2 = PI_Controller(pPIDId[bMotor],

           (int32_t)(FOCVars[bMotor].Iqdref.qI_Component2) - Iqd.qI_Component2);

 FOCVars[bMotor].Vqd = Vqd;

 Vqd = Circle_Limitation(pCLM[bMotor], Vqd);

 Valphabeta = MCM_Rev_Park(Vqd, hElAngle);

 hCodeError = PWMC_SetPhaseVoltage(pwmcHandle[bMotor], Valphabeta);

 FOCVars[bMotor].Iab = Iab;

 FOCVars[bMotor].Ialphabeta = Ialphabeta;

 FOCVars[bMotor].Iqd = Iqd;

 FOCVars[bMotor].Valphabeta = Valphabeta;

 FOCVars[bMotor].hElAngle = hElAngle;

 return(hCodeError);

}

Currents read are stored inside Iab structure. Ia and Ib can be easily send to an oscilloscope thanks to the DAC. The MotorControl monitor allows you to select which information you send to the DAC in the advanced tab.

From this Raw Iab current, we do mathematical transformation into Torque and Flux (Iq and Id) thanks to Clarke and Park transforms.

Iq and Id are then compared to Iqdref, and the error is the entry of the current PID controller.

IqdRef is computed inside the speed regulation loop.

IqdRef.qI_Component1 = STC_CalcTorqueReference( pSTC[M1] );

The torque computation depends on the control mode. In speed mode, the torque is the output of the speed PID. The entry of the PID is the speed delta error.

In torque mode, the iqdref can be set by the motor control monitor or by the MC_ProgramTorqueRampMotor1( int16_t hFinalTorque, uint16_t hDurationms ) API.

In both cases, the current input is expressed in digit.

During open loop start, the reference torque is computed by the workbench based on the different values set in the start-up parameters. The current conversion from amps to digit is done by the workbench.

Hope it helps

Cedric

Hello Daniel,

There is actually no conversion. The target torque is already expressed in digit.

Cedric