I have a position control application with a PXI-7344 card driving two stepper motors on velocity mode. In some circumstances, following a period (1 minute or more) of rapid velocity demand changes the controller appears to add an offset to the velocity that is loaded on one of the axes. The offset value is approximately -4000 steps/sec.
I have put an oscilloscope on to monitor the signals between the card output and the stepper motor drive, and with the velocity demand fluctuating between -2000 and -6000 steps per second I can see the DIR signal fluctuating. For this velocity range it should be steady reverse direction.
Is there a known software bug for this, or is it likely to be faulty hardware?
I am using LabVIEW 2011.
Thanks
Paul