Avoid "double" breakpoint occurence

Question

Hi there,
First post so apologies if missing out on any conventions.
I am setting up a vision inspection system with two stages in xy-configuration controlled by PCI-7350. The samples are located in a grid, which can be slightly irregular due to placing inaccuracy. Previously we stopped for image taking, but now we are switching to using breakpoints to take images "on the fly".
In principle, I have got this working with a buffered array of breakpoints (on x-axis) and using arrays for movements that are blended. However, occasionally it happens that images get lost when switching between two rows as two breakpoints are triggered almost simultaneously. How can this be avoided? I have tried changing the "Requested Interval (10 ms)" input on the "configure buffer.VI", but that did not help.
Could I change the deadband or something like this on the stages? Or do I need to rewrite breakpoint positions to the buffer for every new row? Any suggestions would be most welcome.
A second question (perhaps worthy of it's own thread) would be how to handle the movement more efficiently. The image processing will require a lot of processor resources, so I would like to take care of the movement on board. I have tried a little with buffered contouring, but with little success. I have also seen examples on onboard programming, but not yet given that a go. Which way would the experienced user suggest me to go?
Thanks in advance for your helpful input.
/Anders

Answer 1

Hi,
Thanks for your advice SFK.
I now have a safe zone, which helps, but now I ran into a different problem; For some reason my breakpoints do not always occur.
I have attached  the VI (apologies for mess) and some plots for understanding the problem. In this VI I want to blend two axis movement and write breakpoints to a buffer in between every row. It is sort of puzzled together from two different examples; Sequence of Blended Vector Moves.vi and Buffered Contouring (Rose).vi
Going through the letters to help understanding the purposes of the steps:
A - load breakpoints is an array of the number of breakpoints I want to load for every row. Every other item is a 0 as I move between rows. When I define the buffer sizes I used either the sum of all breakpoints to be loaded or the max number for one row (not visible here). My svanning grid is 12 rows with 10 columns, so 10 is the maximum of points.
B - Old Data Stop (True) is set to false as I otherwise run into an error with old data, i.e. some points have not been triggered. This is the problem I need to avoid.
C - A VI that takes the stage to the starting position, which is a now defined 1mm to the left of the starting point. The start and the endpoint of each rows is 7mm outside of the breakpoint positions (spaced by 7 positions, so the safe zone should be there.
D - Here is where the breakpoints are loaded in case the number is >0. The array with remaining breakpoints is passed. The position where the breakpoints are loaded is added to the plot of the stage movement.
E - Adds where the breakpoints occurs to the plot.
In the attached plots my problem can be seen. The movement starts low left. What is also very puzzling to me is why this pattern looks different depending on how I define the buffersize.
Any help is greatly appreciated.
Thanks,
anders
Attachments:
blend breakpoints vi.JPG ‏211 KB
breakpoints buffersize 10 elements.JPG ‏39 KB
blend breakpoints vi.JPG ‏211 KB