Motion Assistant

[TulioB]

Hi,

What is the defined behavior for Motion Assistant API contour mode (NIMASetMoveParams) when it receives duplicated XY points?
For example, if I pass coordinates that define a square
0,0
10,0
10,10
0,10
0,0
this isn’t result in square because of the cubic spline. To force a discontinuity (C2 and C1) I can replicate two times each point.  For example:
0,0
10,0
10,0
10,0
10,10
10,10
10,10
...
This is valid in spline theory. What the API will do in this case?

Thanks.

[David S.]

Hi TulioB -

The rules for the Motion Assistant contouring algoirthm are that the move accelerates only at the beginning of the contour, moves at a constant speed throughout the contour, and then decelerates only at the end of the contour.  As such, the system will not stop at the corners. 

You'll probably receive an error if your write repeating points the way you showed.  You may be better off using blended moves (with a blend factor of 0) for a shape like this.

[TulioB]

Hi David,

I tried to feed Motion Assistant with replicated data. Neither Motion Assistant application nor the API generates any kind of error. Based on the resulting shape (not a square, but something that resembles a drop) I think that the redundant data is being ignored.

You said that after the acceleration, M.A. will keep the velocity constant. This is not always the case as I discussed in e-mail support “(Reference#7107453) Motion Assistant contouring behavior”. There are situations that the algorithm of the contour mode (or smart contouring feature) implemented in M.A. changes the velocity during the motion.

Another different behavior is the M.A contour mode and the contour mode implemented in the PCI 7344 is that the board doesn’t ignore redundant data as is stated by S. Arves S. in my post http://forums.ni.com/ni/board/message?board.id=240&message.id=3443#M3443 .

It will be very helpful a detailed specification about the rules for the smart contouring implemented in M.A. and the contoured mode implemented in PCI 7344. I’m sure that this will help everyone do a better use of these products.

Thanks.