Motorware speed reading issue

Sam Chen79

Intellectual 390 points

Other Parts Discussed in Thread: TMS320F28069

Hi,

I am facing a motor speed report issue on TMS320F28069 when calling out the following function:

// get the speed estimate
gMotorVars.Speed_krpm = EST_getSpeed_krpm(obj->estHandle);

The number of pole pairs is set to 2, and USER_IQ_FULL_SCALE_FREQ_Hz is set to 800.0

I noticed that when the motor speed was at thousands, such as 1000rpm, 2000rpm, and so on, I got unstable gMotorVars.Speed_krpm readings. The reading can drop to 1000rpm below or 1000rpm above target speed intermittently even though the motor is actually running at the right speed.

For example, when the motor is set to run at 1000rpm, the readings can be swinging from near 0 to near 2000rpm intermittently, although most of the time it reports about 1000rpm. Again, this only occurs at 1000s ranges. It would be fine if motor is set to run at, for instance, 980rpm or 1020rpm.

What could be the reason?

Thank you.

over 9 years ago

0 ChrisClearman over 9 years ago

TI__Guru** 119460 points

you're saying if you set a SpeedRef of 980 RPM, it is very stable around 980 RPM.
But if you set 1000 RPM, you will get huge errors in the SpeedEst? But the motor is not changing speed?

0 Sam Chen79 over 9 years ago in reply to ChrisClearman

Intellectual 390 points

If I set 1000 RPM, I will get huge errors in SpeedEst. However, the motor does change its speed from 980 RPM to 1000 RPM.

Thank you.

0 ChrisClearman over 9 years ago in reply to Sam Chen79

TI__Guru** 119460 points

not clear.

if you set 980 RPM what happens?

which version of CCS? Which version of the compiler?

you can drag and drop your user.h into your response using "Use rich formatting" to attach.

0 Sam Chen79 over 9 years ago in reply to ChrisClearman

Intellectual 390 points

CCS 6.1.1, compiler 6.2.7.

This is what happens:

Set 980 RPM, motor runs 980 RPM, SpeedEst is about 980 RPM.
Set 1020 RPM, motor runs 1020 RPM, SpeedEst is about 1020 RPM.
Set 1000 RPM, motor runs 1000 RPM, SpeedEst has intermittently huge errors.

Similar result applies when set 2000 RPM (1980 & 2020 are okay), 3000 RPM (2980 & 3020 are okay) and so on.

0 Sam Chen79 over 9 years ago in reply to Sam Chen79

Intellectual 390 points

Would it be possible to have your email address to send the user.h to?

Thank you.

0 ChrisClearman over 9 years ago in reply to Sam Chen79

TI__Guru** 119460 points

you can click reply - Use rich formatting

and drag and drop the user.h

but this is completely strange. there is no reason that it would behave this way at all. nothing like this ever brought to our attention in 3.5 years of being released

0 Sam Chen79 over 9 years ago in reply to ChrisClearman

Intellectual 390 points

6708.user.h

0 Sam Chen79 over 9 years ago in reply to Sam Chen79

Intellectual 390 points

Any thoughts on the user.h?

Please see my previous reply above for the user.h. Thanks!

0 ChrisClearman over 9 years ago in reply to Sam Chen79

TI__Guru** 119460 points

this is clearly your own HW with the VOLTAGE and CURRENT settings
your V_A offsets are very low. What Vbus are you using?

USER_VOLTAGE_FILTER_POLE_Hz
is a little high, but shouldn't be causing the problem you describe (nothing could cause the problem you are describing)

your USER_MOTOR currents are TINY compared to your hardware. Why did you design your HW to handle such large currents if your motor is 5A peak? There is certainly some issues with the resolution of your voltage and current signals from the motor vs. the HW.

0 Sam Chen79 over 8 years ago in reply to ChrisClearman

Intellectual 390 points

Yes, this is our own HW. The Vbus can go to 600V max.

You are correct, there has been a voltage and current resolution issue. The problem disappeared when running with a large current motor, such as 70A peak. Thank you for pointing that out!

0 Sam Chen79 over 8 years ago in reply to Sam Chen79

Intellectual 390 points

What would be the reason that the SpeedEst issue only appears at around 1000 RPMs, when there is a motor and HW mismatch?

0 Sam Chen79 over 8 years ago in reply to ChrisClearman

Intellectual 390 points

What would be the reason that the SpeedEst issue only occurs at around 1000rpm, when there is a motor and HW mismatch?

0 ChrisClearman over 8 years ago in reply to Sam Chen79

TI__Guru** 119460 points

Sam, I have no explanation for what you've seen.

"You are correct, there has been a voltage and current resolution issue. The problem disappeared when running with a large current motor, such as 70A peak. Thank you for pointing that out!"

it makes sense that you saw issues with running a smaller motor / smaller Vbus with your inverter...but I can't explain how you would see incorrect Speed Estimates only at multiples of 1000 RPM but not at any other.

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Motorware speed reading issue