TMS320F28027F: Torque Mode - motor continues to spin with Iq_Ref of 0.0

Bump - I could really use some advice here!

Thanks much,

-asifjahmed

Hello,
I am writing to let you know that a C2000 team member has been assigned to this post and should be answering shortly.

Regards
Baskaran

Maybe, the motor should have big inertia, so the motor runs continuously without any torque current for some time. more, please check the feedback Id and Iq when you set the Iq_ref to zero. You can check the feedback current and output (Ui) of the Id&Iq PID regulator. And you need to do offset calibration for this board, the real Id and Iq will be not zero for the current offset is not correct.

The problem is not motor inertia - if i disconnect power from the controller the motor stops much more quickly.

After setting IqRef_A to 0.0 and the motor keeps spinning, the Ui of the Iq regulator (pid structure actually, i'm using lab 11a) stays at a high value (~0.378 in my case, which is near the max allowed value). For some reason the motor just keeps spininng...

I have calibrated my offset values.

Please help.

Other times Ui does go down slowly after setting iqref_a to 0.0 but other times it continues to increase and the motor accelerates...

Monitor the reference, feedback and Ui value of Iq PI regulator, to check why the Ui is decrease slowly. Did you disable the PWM output when you set the Iq_ref to zero?

Hello -

Apologies for reviving an old thread, but I am still having the issue of the motor continuing to spin when IqRef is set to 0.

I'll preface that I've now tested this on the DRV8301-REVD board, and the issue is not present. However, my board was modeled after this one.

The issue does not occur on every motor. I have a few hub motors that are relatively low speed (<1500 rpm) and I do not seem to have the issue. However, with higher-speed motors (~8000rpm) the issue exists.

At this point I realize that it must be something in my hardware, but the schematic is modeled after the DRV8301-REVD board.

Can someone please provide guidance on how to diagnose the cause of this issue? I really appreciate

-asifjahmed

UPDATE:

This issue is still occuring even after I completely redesigned my PCB.  I have now noticed that when I use a 25V battery, this issue does not occur, and when I set IqRef_A to 0.0 the motor spins down and comes to a stop. However, when I use a 50V battery, the motor will not stop spinning. It just keeps spinning and spinning, even with a IqRef_A of 0.0. The Ui of each PI loop does not return to 0. FYI, all components in this circuit can handle >50V.

I thought this was due to parasitics in my PCB causing ground loops/EMI. I had a few flaws on my PCB where my return paths on the gate driver were not good (large return path), so I redesigned my PCB using shorter, fatter, paired traces. Issue still occurs.

This is a major problem for me now. I would really appreciate some support on this matter. How to even diagnose this issue? I have spent countless hours redesigning PCBs to no avail. I'm willing to do whatever I need to do to resolve this issue, I  just need assistance on where to look...

Best Regards,

asifjahmed

Bump again. I would really appreciate some help here.... This is affecting my business and I need help resolving this issue. Please...

1. Does the motor stop immediately if adding some load and set IqRef_A to 0?
2. Did you turn off the pwm output if you want to stop the motor? You can turn off the pwm output to stop the motor when setting IqRef to 0 at the same time.
3. Was the Id and Iq feedback value when setting the IqRef_A to 0? The motor can't stop immediately, even run for a long time as you met if the current feedback signal is not good and offset is not calibrated correctly.

The motor does stop if enough load is added. Without enough load (but small load) the motor keeps spinning. Again, this is at 50V. At 25V, this issue does not occur. Obviously the motor is spinning twice as fast at 50V.

I do not turn off the PWM output. I should not have to right?

The feedback does not go to 0. I will get some specific numbers for you here.

OK, the feedback goes nearly to 0, but the Ui stays around the same level, instead of winding down

Did u sed the ADC_FULL_RANGE correctly? (Depends on your voltage-divider on Phase-voltage measurement). Do u have RS-Recalc activated? What is your RsOnLineCurrent_A ? On zero speed the motor uses a current to measure the resistance. I hat issues because the default Current of 1A was high enough to spin the motor. I am not sure if it works like that but give it a try.. lower RsOnLineCurrent_A or deactive the recalc

Thanks for your reply Sebo! My ADC_FULL_RANGE is correct (re-calculated based on the resistors). Unfortunately I am not using RsOnline so that is not the issue.

UPDATE:

I realized that my current scaling was off. I modeled the board after the DRV8301_REVD board, and didn't realize that the board uses external current sense amps, not the ones in the DRV8301. Thus, I had my calcs setup for a 10V per V scaling, when the REVD board uses 20V per V.

All this though, and after fixing the values (by both trying to use only 2 current sensors and setting the DRV to 20V per V and also just doubling my ADC_FULL_SCALE_CURRENT value. The problem still exists...

What else to look for? I think my current waveforms may be too noisy, but I used differential pairs and everything...

Please help! And if it would be better suited for me to call someone at TI for better assistance, please advise. I'm really stuck with this issue and it is affecting my business.

Best,
-asifjahmed