Contour move: how to get interval 2ms

[dluu]

Hi all,

I am trying to get an interval of 2ms on the contour move.

I am using a NI PXI-7350, along with LabVIEW 2010.

I used a slightly modified One-Axis Contour Move example.  The only change I made is that instead of reading the array that is given in the example, I deleted that and instead, read from a spreadsheet file.

When I set the "requested interval" on the front panel of the example VI to anything smaller than 10ms or so, the "actual interval" indicator shows 0ms.

I have checked my settings in MAX, and the control loop update period is 250 microseconds, which is smaller than the contour interval I want to do, so it should be alright.

Is there a setting in MAX that I am missing?

I have attached a copy of the program (without the modification; I get the same problem no matter which contour I use).

[Cole_R]

Hi dluu,

Unfortunately, the minimum interval for your PID rate is going to be 10 ms.  You can find a chart for the minimum and maximum intervals for different PID rates in the LabVIEW help for the Configure Buffer VI.  Also, the overall minimum for the rates listed is 10 ms, so it seems that this is going to be a limitation of the hardware itself.  Sorry I didn't have a solution for you but I hope this helps!

[dluu]

Thanks,

Is it just the 7350 that has the limitation?

If not, can you recommend a card that has a faster update time?

[dluu13]

I also looked into the 7390.  It seems that it doesn't have contour capabilities, but if I were to use a trigger sort of mechanism to start the movement, how fast does it respond?

[Cole_R]

It looks like 10 ms will be the limitation for the 73xx boards.  We do have soft motion modules that run on the cRIO that can be used to get a little faster.  In the specifications, it states that the interval must be a multiple of the scan period which has a minimum of 1 ms.  Although, if you're not familiar with cRIO, this platform will be very different from using the motion control boards.