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INSTASPIN-BLDC: Estimate Ls without spinning the motor

Colin Schmidt
Prodigy 40 points
Part Number: INSTASPIN-BLDC

Hello!

We have a bit of a problem with the Instaspin FOC. We are using a BoostXL DRV8301 Rev.B attached to a F28069M LaunchPad to control a small brushless inrunner motor with 2 poles and rated for 2700KV.

Everything runs perfectly after we estimate the parameters of the motor and we are able to control it very well. However, things change completely if we change the motor with another one of exactly the same kind, same supplier etc. The motors should be identical but apparently Instaspin thinks they are not.

If we change the motor we have to go through the entire estimation phase again. This is not acceptable for normal use as we cannot have the motors taken out of the system in order to run them without a load to get the estimated parameters. It is also very time consuming to estimate the parameters of every single motor.

An option would be to be able to estimate Ls without spinning the motors. Is there any possibility to do this? Or, is there any possibility to control the motors while ignoring Ls?

Any suggestions would be very appreciated.

Thanks,

Colin

  • 0
    TI__Guru** 111170 points

    No, you must get the correct motor parameters by running the lab02c. No any other shortcuts, you have to tune the identification variables as below according to the spec. of the motor, to keep the motor spin smoothly to get all the parameters properly.

    #define USER_MOTOR_RES_EST_CURRENT 

    #define USER_MOTOR_IND_EST_CURRENT

    #define USER_MOTOR_MAX_CURRENT

    #define USER_MOTOR_FLUX_EST_FREQ_Hz 

  • 0 in reply to Yanming Luo
    Prodigy 40 points

    Yes, I understand that... But, what can we do if we have 1000 motors we need to run? These motors are supposed to be all the same but if we change one which is already tuned with another, it will not work anymore. It seems that the slightest difference in inductance will completely throw off the entire control algorithm...

    Instaspin is a great way to control a motor but it's pretty much useless outside of the lab/test bench. How are we supposed to use this in production?

    All the best,

    Colin

  • 0 in reply to Colin Schmidt
    TI__Guru** 111170 points

    Have to assume all the motors have a little bit difference between their parameters (less than 5%, or 10% depends on the control performance requirement). Generally, the motor should be easy to meet the spec. If not, you have to tune/identify the motor one by one.