Interpolation of curve with loops

[Bob_Y.]

I have an image on which I need to select points and then use motion control to etch the curve defined by my points. Motion Assistant cannot import my image, so I am building my own interface in LabVIEW.

Here's how I have it working now:

Get the image in LabVIEW
Define the points in LabVIEW
Export them to file
Import the file into the Motion Assistant
Use contouring to smooth things
I usually get the desired curve (near as I can tell without the image) and can begin the etching process.

When I do not get the desired curve, I need to start over and define a few more points in the problem region. This is tedious and not the user friendly UI that a customer would want.

I would like to perform the same or similar interpolation as the Motion Assistant's contouring on my image in LabVIEW then use the motion control VIs to do the etching. Is there a way to do contouring style interpolation?

I tried to use the spline interpolation, but my defined curve often has places where there can be loops (the curve crosses itself) or at least multiple Y points for a single X value (such as vertical lines or double-backs) and the spline interpolation that is included with LabVIEW errors. Is there another way to do it? I mean, I know that it works in the Motion Assistant so I know that there is a way to do it, the real question is how to get at the algorithm that the Motion Assistant uses or something similar.

Thanks,
Bob Young

[Scott_R]

Hello Bob,

Have you looked at the contouring shipping examples for LabVIEW? They can be found at:

C:\Program Files\National Instruments\LabVIEW 7.1\examples\Motion\FlexMotion\Contouring.llb

For your application, I would suggest looking at Buffered Contouring(Rose).vi and Two-Axis Contouring(Spiral). Those examples make use of 2-D contoured motion.

Take a look at those and let me know if you have any additional questions about contouring.

Regards,
Scott R.
Applications Engineer
National Instruments

[Rodj]

Bob,

As of Motion Assistant 1.2.1 you can use the functionality of Motion Assistant programmatically in LabVIEW. If you have a copy of Motion Assistant 1.2.1 take a look at its examples and tutorials to learn how to use its new API. Motion Assistant 1.2.1 is a free upgrade from previous versions of Motion Assistant.

If you don't have a copy of Motion Assistant, you can download a 30 day full-featured evaluation copy from the web. Just copy the link below into your web browser.

http://digital.ni.com/demo.nsf/websearch/2D9A192EB1C0B04686256BCD006B6517?OpenDocument&node=157200_US

I also recommend you check out the article "10 Essential Technologies for High-Performance Motion Control" located at:

http://zone.ni.com/devzone/conceptd.nsf/webmain/E7ABA6F4D569010A86256F5A005B64F3?opendocument&node=11091_US

The first point of the article is "Smart Contouring" which is the feature you are interested in using.

Thanks,

Rodger S.
Motion Control Group Manager
National Instruments