Modeling S-Curve acceleration and Deceleration?

[matthewg]

Hello,

I would like to model the response of a motor to a step change in target position. I currently have an EC motor and a PXI-7358 motion controller card, using LabVIEW.

I am a little confused as to how to model the S-curve smoothing. I can't seem to find much information about how the motion controller does this, other than this article. 

I can specify the max accel and velocity. Does the motion controller use some sort of logic to say "if the actual motor acceleration is higher than the max value, then the output voltage command should be zero, until the motor slows down below the max acceleration"? Or is there a hidden PID loop that controls the velocity and accel? 

Through some tests, I've observed that the max velocity and acceleration can sometimes be exceeded with a large step, and that the velocity might fluctuate about the maximum velocity. So that's why I wonder if a hidden controller is keeping the velocity and accel close to the maximum values that I input. My modeling so far has not been too successful. 

Thanks.

[iZACHdx]

Hello,

You can try using the Motion Assistant to generate move profiles. The profiles generated there would match the profiles that were actually generated on the card. Basically, the motion controll is going to perform a move, then calculate the current position versus target position. At that point, it would perform a pull-in move to correct for any discrepancy.

-Zach

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[Joe D.]

Hi hanyang,

Your best option is to contact you regional NI branch. Here is there contact info:

Tel: 021-50509800 或 852-26453186
E-mail customer service
Fax: 021-65556244 或 852-26453186

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