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Lab 7 – Using Rs Online Recalibration

user4708725
Expert 1030 points


Evaluation board:  drv8301-hc-evm revd

Lab 10a  Overmodulation

In Lab 10a  Overmodulation,I add  Rs Online Recalibration,butRs Online Recalibration is inaccurate,

The online identification of Rs is inaccurate, with an error of 10 milliohms. Our product requires an error of 2 milliohms to be acceptable.

What factors affect the accuracy of motor resistance identification? What values are appropriate for the following parameters?

1. gMotorVars.SpeedRef_krpm？

2. gMotorVars.MaxAccel_krpmps？

3. RsOnLineCurrent_A？

The motor parameters are as follows

Nominal voltage V                  24

No load speed rpm                60800

No load current mA               282 

Nominal speed rpm               57500

Nominal torque (max. continuous torque) mNm           23.6

Nominal current (max. continuous current) A               6.45

Stall torque mNm                  561

Stall current A                      149

Max. efciency %                   91.6

Terminal resistance W         0.161

Terminal inductance mH     0.0171

Torque constant mNm/A     3.76

Speed constant rpm/V        2540

Speed/torque gradient rpm/mNm      109

Mechanical time constant ms            2.04

Rotor inertia gcm                               1.79

  • 0
    TI__Guru** 116420 points

    As we have replied to the thread you posted, please refer to chapter 15 of InstaSPIN user's guide that has a detailed description of Rs Online Recalibration. You may enable the Rs Online Recalibration when the speed is constant, and don't enable it during the acceleration or deceleration phases. The RsOnLineCurrent_A should be more than 5% of the rated current of the motor. A higher injection current will get a good recalibration Rs.


  • 0 in reply to Yanming Luo
    Expert 1030 points

    I've tried all the methods you said, and the accuracy of resistance identification has really improved.
    But for the first time, the second time and the third time after downloading the program, the RS deviation of the identification is large.
    Fourth, fifth and sixth, the RS deviation of identification meets the requirements.
    How to solve the problem of large deviation of the previous Rs identification? Our product requires an Rs identification.

  • 0 in reply to user4708725
    TI__Guru** 116420 points

    Try to increase the injection current, and just enable the Rs online calibration when the motor is running under the rated speed, and without a larger vibration on load. It's not easy to meet your requirement on the error rate (2mOHM), that is not reasonable since the resolution of the current and voltage sensing circuit is only 1%. You have to design your own board with higher resolution tolerance of the sensing circuit if you want to get such error on Rs.