Rs-Online Accuracy

MKo

Hello,

I've got two questions regarding your Rs-Online identification:

(1) Do you have some numbers how accurate the identified Rs-values are under different load and inductance conditions? 5%, 10%, 15%? I am especially interested in high R (1-2Ohm) over L (10-100µH) motors.

(2) I guess you can't provide any further details (apart from what is written in spruhj1d) on how you perform the estimation (IEEE papers, patents, etc.)?

Thanks.

over 11 years ago

0 ChrisClearman over 11 years ago

TI__Guru** 119680 points

1. This is calculated by a direct measurement of voltage and current, so it's as accurate as the sensor signal chain. How accurate is an ohm-meter you are using?

2. Correct, this is TI intellectual property that is already published as extensively as we will.

0 MKo over 11 years ago in reply to ChrisClearman

Intellectual 310 points

ChrisClearman said:

1. This is calculated by a direct measurement of voltage and current, so it's as accurate as the sensor signal chain. How accurate is an ohm-meter you are using?

If you are using a flux observer you need a machine model which is never perfect and your Rs estimation might depend on things like inverter non-linearity effects, permanent flux linkage, inductances Ld/Lq and I_d current amplitude. Some of these can't be determined exactly or even vary. For this reason other Rs estimators I know of reach accuracy values of about 10%. Also motor temperature estimation may become useless if Rs uncertainty is too large.