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Smooth velocity profile for stepper motor control with LIFA?

I need to run a stepper motor at two different velocities during a motion. I'm currently using a sequence structure with a Stepper Write.vi in each frame, with different speed values being fed into the subVI in each frame. When I run the program, however, the motor stops and then starts again at the transition, instead of smoothly changing speeds. I am pretty inexperienced with LIFA and with LabVIEW in general, so I may be missing something obvious, but how can I create a smooth, custom velocity profile? Can I do it with Stepper Write.vi or do I need to use a different approach?

 

Thanks for the help!

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cterill,

 

Looking at the code behind the LIFA stepper VI's, I don't see any kind of trajectory generation algorithms which would be required in order to control the acceleration and jerk parameters. It is possible this can be controlled via your drive, but from what I can tell, the acceleration and jerk seem to be limited only by the physical characteristics of the system and electrical characteristics of your drive.

 

Generating these profiles manually isn't trivial, but with a basic understanding of differential equations it's not terrible either. Without going in to a full discourse, one good explanation I have found is located here:  http://www.ni.com/white-paper/3367/en/ A google search for "motion velocity profile" will turn up many more detailed articles as well.

 

Whether you need trapezoidal or s-curve profiles simply depends on how tolerant your system is of jerk.

 

Just so you know, there is an arduino community located here: https://decibel.ni.com/content/groups/labview-interface-for-arduino  You will often get a better response there due to the large number of users with in-depth Arduino experience. Also, LIFA is deprecated and it is recommended you move to LINX. I can't provide a whole lot of information on LINX, but more can be found in the ardunio community.

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