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NI SoftMotion Development Module Shipping Example "Servo Position Loop" exhibits jerky movement

Primary Software: LabVIEW Modules>>SoftMotion Development Module
Primary Software Version: N/A
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
Why does the "Servo Position Loop" shipping example of the NI SoftMotion Development Module (SMDM) 2.1 and lower exhibit jerky motion?

Solution:
There is a bug in the shipping example that causes this behavior. The bug will not be fixed until the next release of SMDM, but can be easily fixed by the end user.

Bug:
The control "Spline Data Updated - Axis 1" on the front panel of "Servo Position Loop (FPGA).vi" has its mechanical action set to "Latch When Released". The example is written expecting the mechanical action to be set to "Switch When Pressed". The incorrect mechanical action causes the FPGA code to only detect every other Spline Update and thus the motion pauses every other RT loop iteration.

Fix:
Change the mechanical action of "Spline Data Updated - Axis 1" to "Switch When Pressed".


NOTE 1: There are other less severe problem with the "Servo Position Loop" shipping example. Attached to this KB is the "Servo Position Loop" example modified with the known bugs fixed. The attached example was built using NI SoftMotion Development Module 2.1 and LabVIEW 8.2.1.


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Report Date: 10/03/2007
Last Updated: 12/28/2007
Document ID: 4E2891AJ

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