CCS/BOOSTXL-DRV8301: When should I read currents if I use Direct torque control approach?

Ata Khiabani

Part Number: BOOSTXL-DRV8301
Other Parts Discussed in Thread: MOTORWARE, , CONTROLSUITE

Tool/software: Code Composer Studio

Hello,

I am trying to implement direct torque control on a PMSM. I have used ADC interrupt, and an EPwm triggers EOC interrupt. In my ISR, I read the current and voltage values, as well as encoder values for speed and position calculation and implement the DTC approach. My Epwm configuration for interrupt and ADC configurations are as follows:

void ConfigureEPWM(void)
{
    EALLOW;

    EPwm4Regs.TBCTL.bit.CTRMODE = 3;            // Freeze counter
    EPwm4Regs.TBCTL.bit.HSPCLKDIV = 0;          // TBCLK pre-scaler = /1
    EPwm4Regs.TBCTL.bit.CLKDIV = 0;          // TBCLK pre-scaler = /1
    EPwm4Regs.TBPRD = 2500;                   // Set period to 2000 counts (50kHz)
    EPwm4Regs.TBCTR = 0x0;
    EPwm4Regs.TBCTL.all=0x1C;
    EPwm4Regs.ETSEL.bit.SOCAEN  = 0;            // Disable SOC on A group
    EPwm4Regs.ETSEL.bit.SOCASEL =1;           
    EPwm4Regs.ETSEL.bit.SOCAEN = 1;             // Enable SOCA
    EPwm4Regs.ETPS.bit.SOCAPRD = 1;             // Generate pulse on 1st event

    EDIS;
}

void SetupADCEpwm(void)
{
    EALLOW;


    AdcaRegs.ADCSOC0CTL.bit.CHSEL = 2;
    AdcbRegs.ADCSOC0CTL.bit.CHSEL = 2;
    AdccRegs.ADCSOC0CTL.bit.CHSEL = 2;
    AdcaRegs.ADCSOC1CTL.bit.CHSEL = 3;
    AdcbRegs.ADCSOC1CTL.bit.CHSEL = 3;
    AdccRegs.ADCSOC1CTL.bit.CHSEL = 3;
    AdcaRegs.ADCSOC2CTL.bit.CHSEL = 0xE;



    AdcaRegs.ADCSOC0CTL.bit.ACQPS = 14;         
    AdcbRegs.ADCSOC0CTL.bit.ACQPS = 14;         
    AdccRegs.ADCSOC0CTL.bit.ACQPS = 14;        
    AdcaRegs.ADCSOC1CTL.bit.ACQPS = 14;        
    AdcbRegs.ADCSOC1CTL.bit.ACQPS = 14;         
    AdccRegs.ADCSOC1CTL.bit.ACQPS = 14;         
    AdcaRegs.ADCSOC2CTL.bit.ACQPS = 14;         

    AdcaRegs.ADCSOC0CTL.bit.TRIGSEL = 0xB;        // Trigger on ePWM4 SOCA/C
    AdcbRegs.ADCSOC0CTL.bit.TRIGSEL = 0xB;        // Trigger on ePWM4 SOCA/C
    AdccRegs.ADCSOC0CTL.bit.TRIGSEL = 0xB;        // Trigger on ePWM4 SOCA/C
    AdcaRegs.ADCSOC1CTL.bit.TRIGSEL = 0xB;        // Trigger on ePWM4 SOCA/C
    AdcbRegs.ADCSOC1CTL.bit.TRIGSEL = 0xB;        // Trigger on ePWM4 SOCA/C
    AdccRegs.ADCSOC1CTL.bit.TRIGSEL = 0xB;        // Trigger on ePWM4 SOCA/C
    AdcaRegs.ADCSOC2CTL.bit.TRIGSEL = 0xB;        // Trigger on ePWM4 SOCA/C


    AdcaRegs.ADCCTL1.bit.INTPULSEPOS  = 1;  // 1 = INT at the end of conversion
    AdcaRegs.ADCINTSEL1N2.bit.INT1SEL = 2;      // End of SOC2 will set INT1 flag
    AdcaRegs.ADCINTSEL1N2.bit.INT1E = 1;        // Enable INT1 flag
    AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1;      // Make sure INT1 flag is cleared


    EDIS;
}

So the ISR appears each 25uS and the ADC values are read and the algorithm is implemented and if the ISR finishes before 25uS, there is an infinite loop in "main". I am able to run the motor but it is not smooth, I have checked the algorithm and it is fine. The question is that is there any specific time that I should read the currents? because I think maybe the current readings are not correct.

Thank you for your help.

Regards,

Ata

over 6 years ago

0 Sanmesh Udhayakumar over 6 years ago

TI__Expert 6065 points

The expert assigned to this part is out of office, but will be available monday.

0 Ata Khiabani over 6 years ago

Intellectual 780 points

Could you please help me with this issue?

Thank you.

0 Sanmesh Udhayakumar over 6 years ago in reply to Ata Khiabani

TI__Expert 6065 points

This was reassigned to the C2000 group since this is a more algorithm question. The person assigned to this may be out due to july 4th holiday. I will send a reminder to the group, but they may be out and return to you next week.

Your question is regarding when to sample current. Are you using the esmo code base or the instaspin motorware code base? I would guess that when to read the currents depends on the motor control algorithm

0 Yanming Luo over 6 years ago in reply to Sanmesh Udhayakumar

TI__Guru** 115450 points

That depends on the algorithm and h/w board you used. You should trig the ADC sample during the high-side FETs are off, and low-side FETs are on if you are using boostxl-drv8301 board, and read the sampling result in the control ISR.

Btw, you might refer to the example motor control code about PWM and ADC configuration in controlSUITE that can be used for DTC also.

0 Ata Khiabani over 6 years ago in reply to Yanming Luo

Intellectual 780 points

Thank you for the response.

But in DTC the Fets are on or off for the whole sampling time period. So suppose two high side Fets are on and only one is off, so I can only measure one current in that case? Is it possible to read all three currents and EOC start the ISR?

0 Yanming Luo over 6 years ago in reply to Ata Khiabani

TI__Guru** 115450 points

You can read all three currents, but only two values of these three currents are valid every time, so you have to add a function to resolve this by yourself. The reference code in controlSUITE doesn't have such function.

0 Ata Khiabani over 6 years ago in reply to Yanming Luo

Intellectual 780 points

Thank you for the response. Could you please explain this point a little more? I am assuming because the ADCs are floating and are not pulled-down, when a low switch is off, the ADC reads a value and this results in an invalid current reading. right? Does TI have a document that explains this?

0 Yanming Luo over 6 years ago in reply to Ata Khiabani

TI__Guru** 115450 points

You might have a look at chapter 17 of instaSPIN user's guide (SPRUHJ1G) that have a very detailed description of the low side shunt current sensing.

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CCS/BOOSTXL-DRV8301: When should I read currents if I use Direct torque control approach?