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LAUNCHXL-F28027F: The estimation of stator inductance identification is inaccurate and Speed closed loop operation is unstable

Part Number: LAUNCHXL-F28027F
Other Parts Discussed in Thread: BOOSTXL-DRV8305EVM

Hi.

We used the LaunchXL-F28027F+ Boostxl-DRV8305EVM demo board to to drive the 24V BLDC. The actual parameters of the motor are: stator resistance 0.15Ohm, The stator inductance 13.5uH, flux 0.00831 V/Hz.the motor needs to run stably in low speed light load, low speed heavy load(300rpm) and high speed light load(40000rpm) three working conditions .

Regrettably,The estimation of stator inductance identification is inaccurate using routines proj_lab2b to identify motor parameters(resistance and flux estimation is accurate),And  in the case of actual motor parameters used in the use.h file ,the speed closed loop operation is unstable ——The same Kp,Ki value is difficult to apply over the full load range (only 300rpm).

All my problems came from speculating about the cause of erratic motor operation(using routines proj_lab5b):

1. Is it normal for the estimated rotor phase Angle to occasionally jump? Is it the cause of the unstable operation of the motor?

2. Whether  "the estimated rotor phase Angle to occasionally jump" and "The estimation of stator inductance identification is inaccurate" are intrinsically related?

3. The problem has to do with the wrong KpKi value? It seems that the recommended KpKi values are not suitable for different load situations.

Looking forward to your help,thanks!

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#ifndef _USER_H_
#define _USER_H_
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  • 1. Please try to use lab02c to identify the motor parameters without load since the motor is a low inductance motor. 

    2. You may try to tune the speed PI controller with different Kp and Ki for low speed and high speed. And don't expect the same performance as high speed at such low speed since the motor is a high speed motor.

  • Hi,Mr. Luo.Thank you for your reply.

    Operation stability has been improved to a certain extent using a different set of KpKi parameters in the case of low speed overload, But the range of loads the motor can operate is not wide enough.

    1.Can I series a filter inductor between the three-phase voltage output and the motor side? Does this help improve the low-speed performance of high-speed motors?

    2. Whether the motor stator inductance value(USER_MOTOR_Ls_d,USER_MOTOR_Ls_q) needs to add filter inductance value when the filter inductor is connected in series?

    thanks!

  • Both are NO. Just keep tuning the PI controller parameters, and make sure that the motor parameters are identified correctly with lab02c.

  • Hi,Thank you for your reply.

    Do you mean that whether filter inductor is added or not has no effect on USER_MOTOR_Ls_d,USER_MOTOR_Ls_q value?

    Is it necessary to re-estimate the parameters?

  • You can't add any filter inductor to motor wires that will have impact on motor control, the motor model will be incorrect to estimate the rotor angle and speed by InstaSPIN.

    Yes. If you change anything on the motor, you need to re-estimate the parameters.

    • I found 28069F has the function of " Initial Position Detection and High Frequency
      Injection
      "---(lab21).Does it help to improve the performance of my motor(sensorless) with low speed and heavy load? And is its code portable to 28027F If this feature might work?

      thanks!
  • And Is there any suitable solution Ti can recommend to improve the low-speed stability of high-speed motors?Can you provide some suggestions on the algorithm and motor or circuit for rectification?

    thanks.

  • Yanming is currently out of the office, please expect our next reply by this Friday the 15th.

    Best,

    Matthew

  • You may have to use the sensored-FOC if you need to start and run the motor at zero/very low speed with heavy load. The IPD and HFI (lab21) is only for an interior permanent magnet synchronous machine ((IPMSM) with significant saliency ratio (Ld<<Lq).