time varying velocity input for servo motor

[Greece]

I 'm running a PXI-8145RT CPU with a 7344 motion controller.I want to load a time varying velocity profile for my servo motor.How can I do this? The "load velocity" tile does not have an input for such a profile,but only for a maximum velocity that will be reached after a certain time.

[Bob_Y.]

You might try the program included in this link. I have not used it but I found it researching another problem.

Hope that this helps,
Bob

[Greece]

Thank you for your interest, but I 'm afraid that these vi's won't do my job.
The profile of the trajectory that I want to achieve is not necessarily a ramp. Imagine that it could have a shape like a "gaussian" distribution.
In the attached file you can have a look of what kind of velocity profile do I want to generate.
Any idea is welcome!
Thanks for your time.

[Bob_Y.]

Are you using the Motion Assistant or a programming language like LabVIEW? If you are using the motion assistant, you can do a contoured move with a Position-Velocity-Time Profile. I have never done this, but it sounds to be what you are looking for. This assumes that you have a controller that can do contoured moves.

Hope that this helps,
Bob

[RManion]

Hi Greece,

If you are looking to make a move similar to the move outlined in the image you have attached, I would recommend making S curve moves. With an S curve move, the velocity profile is not a simple trapezoid but rather a curve in which the rate of change of velocity is smooth and differentiable.

For more information on S curves I would look at chapter 4 of the NI - Motion User manual, in which the different type of moves are outlined.

(The NI Motion User Manual should be installed with the motion driver, and a shortcut can typically be found on the start menu.)

Let me know if this helps,

Robert
Applications Engineering
National Instruments