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Acquisition of Back EMF Signals

Ali Asad
Prodigy 10 points

Hello,

I am in the process of evaluating Back EMF SMO against InstaSpin FAST. Here, I need to compare actual back-emf alpha-beta components versus those obtained from the SMO. I looked in the estimator documentation and found references to the following functions that return back-emf ,

void  EST_getEab_V (EST_Handle handle, MATH_vec2 *pEab_V);
void  EST_getEdq_V (EST_Handle handle, MATH_vec2 *pEdq_V);

Unfortunately, these two functions do not appear to be linked in the FAST library and therefore result in linker error at build time.

So, I request you to provide a workaround for back-emf acquisition in firmware.

Also, please clarify the differences between the following functions in CTRL module and which of them should be used as input voltage for Back EMF SMO.

void CTRL_getVab_in_pu (CTRL_Handle handle, MATH_vec2 *pVab_in_pu) ; 
void CTRL_getVab_out_pu (CTRL_Handle handle, MATH_vec2 *pVab_out_pu) ;


Thank you.

Regards,

Ali Asad

  • 0
    TI__Expert 5180 points

    Hi,

    EST_getEab_V and EST_getEdq_V are not implemented in the currently released ROM. These functions and others will be available in future devices with new ROM code. Actually, any code under "float" folders are not implemented in current devices.

    Unfortunately there is no way to extract the back EMF from the currently released ROM. What you can use to compare SMO with InstaSPIN is to capture the estimated angle and estimated speed from both algorithms and compare them against an encoder or RPM meter.

    As far as the second question goes, CTRL_getVab_in_pu returns the clarke transformed input phase voltages, sensed with the ADC through a resistor divider.

    The CTRL_getVab_out_pu function returns the output voltages in alpha and beta, which will be inputs the the SVM module to produce three phase duty cycles.

    -Jorge