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Original question:

INSTASPIN-BLDC: RsRecalc and Offsets Recalculation time reduction

INSTASPIN-BLDC: Instaspin Rs Recalculation error

Colin Schmidt
Prodigy 40 points
Part Number: INSTASPIN-BLDC
Other Parts Discussed in Thread: DRV8301

Hello,

I'm trying to run 2 BLDC motors using the lab6e example. I need to recalculate the Rs before every start and I enable this in the code with this line: 

EST_setFlag_enableRsRecalc(estHandle[mtrNum],true);

However, the calculated Rs value is different each time and sometimes the value is more or less close to the measured value of 0.24 (calculated with lab2c) but most of the times it is way off, in the range of 1.8 to 3.2.

Any ideas about how could I get a reliable Rs recalculation every single time?

If I use the value calculated in Lab2c, the motors run more or less fine but they don't start reliably at very low rpm.

Also, what I have noticed is that sometimes, when the calculated value is off (way different than the one calculated in Lab2c), the motor runs much smoother at very low rpm. So... maybe the value calculated in Lab2c is not the correct one. I really don't know which is the correct value as I don't have full specs for these motors.

The board I'm using is a BoostXL DRV8301 Rev.B attached to a F28069M LaunchPad and the motor is a small brushless inrunner motor with 2 poles and rated for 2700KV. I need to run this motor from 60rpm up to 10000 rpm. I can to that with a simple brushless controller with an AVR or Microchip MCU but have not been able to do it reliably using Instaspin.

I would really appreciate any help.

Thank you in advance,

Colin

  • 0
    TI__Guru** 116350 points

    What PWM and ISR frequency are you using for dual motor control? And did you enable the Rs recalculation for two motors at the same? The ISR frequency must be lower than 10kHz for dual motor control limit to CPU frequency. 

    You may try lab02c first and increase the USER_MOTOR_RES_EST_CURRENT since your motor is low resistance and inductance motor. It seems like instaSPIN-FOC should be ok for your application, you may try lab10d that is a lab for dual motor control with instaSPIN-FOC since instaSPIN-Motion need to take more CPU bandwidth than instaSPIN-FOC.

  • 0 in reply to Yanming Luo
    Prodigy 40 points

    Hi Yanming,

    Thank you for your answer. I have tried dual motor control using Lab10d and it seems to work much better. Rs is calculated correctly every time.

    What is the maximum PWM and ISR frequency for dual motor using Instaspin-FOC? Is it the same (10KHz) as for Motion?

    Thanks again,

    Colin

  • 0 in reply to Colin Schmidt
    TI__Guru** 116350 points

    The ISR frequency is less than 10kHz is good, the same for InstaSPIN-Motion.