C2000-DIGITAL-CONTROL-LIBRARY: C2000-DIGITAL-CONTROL-LIBRARY

Chen Li7

Part Number: C2000-DIGITAL-CONTROL-LIBRARY

I am confused with SMO module in DMC MATH. Why is there es(n) in the equation of sliding mode observer? According to your description in the document, by filtering z, we can obtain back emf. But If there is es(n) in the equation of sliding mode observer,the value of es(n) should be estimate back emf and the average of z will be zero when the observer reach stable. In this case, the result obtained by filtering z should be zero, right?

over 6 years ago

0 Ramesh Ramamoorthy over 6 years ago

TI__Mastermind 27240 points

The input signal is a continuously varying ac quantity and the steady state error cannot be zero. By sliding mode approach, the error is being pushed close to zero. There are tech pubs available online for your search

0 Chen Li7 over 6 years ago in reply to Ramesh Ramamoorthy

Prodigy 90 points

My question is that because the error is being pushed close to zero, the result obtained by filtering z should be zero rather than back emf, right?

0 Ramesh Ramamoorthy over 6 years ago in reply to Chen Li7

TI__Mastermind 27240 points

Actually, it works other way around. In order for the steady state currenet error to be zero, the back emf estimate should be close enough to the actual bemf. This is possible only if the output of the smo is sinusoidal. Of course, the filtering effect will insert a phase delay and needs compensation. This is taken care off in the eSMO.

0 Chen Li7 over 6 years ago in reply to Ramesh Ramamoorthy

Prodigy 90 points

Could you give me a derivation about estimated bemf in your document? I can't get the result like that in your document.

Thank you

0 Ramesh Ramamoorthy over 6 years ago in reply to Chen Li7

TI__Mastermind 27240 points

You already have that derivation in the form of difference equations. We dont have anything else.
You can simulate the system if you have simulation tools (such as MATLAB) and see for yourself how it behaves dynamically.

0 Ramesh Ramamoorthy over 6 years ago in reply to Ramesh Ramamoorthy

TI__Mastermind 27240 points

If you have no more queries, let us know if we can close the thread. Thanks.

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