We are using the PCI-7344 Motion Controller to drive 4 off step

[George]

per motors. We are running into unexpected speed limitations with the motors. Increasing the speed and acceleration past a certain point (which is well below the motor's and motor driver's capabilities) makes no difference to our period of our cycle. Why?Most of the motion has been programmed as Onboard firmware for maximum speed.
Also we have strange timing issues where the Onboard programs seem to skip sections of code. Is this related?
3 of the steppers are constantly accelerating/decelerating and the 4th is in constant velocity mode.
All four motors are running in open loop with sensors wired to limit inputs and the digital ports for feedback.
I am not missing any steps as the target
is usually reached.
I have checked the speed limits setup in MAX. Ours speeds are well below these values.
I have set the Onboard loop update rate to be 313usec.

Thanks in advance.

George

[Stu 708]

per motors. We are running into unexpected speed limitations with the motors. Increasing the speed and acceleration past a certain point (which is well below the motor's and motor driver's capabilities) makes no difference to our period of our cycle. Why?This sounds similar to a situation that I ran into a while back. the root cause of my problem was overhead of the controller and it's architecture relative to very small, very fast moves. The overhead in a move even when using onboard programs was much more than I expected. I ultimately had to use a different controller.
Stu

[Jayson]

per motors. We are running into unexpected speed limitations with the motors. Increasing the speed and acceleration past a certain point (which is well below the motor's and motor driver's capabilities) makes no difference to our period of our cycle. Why?Stu,
I just saw your posting and wanted to mention that this is a known issue and there is a patch to correct it at:
ftp://ftp.ni.com/support/motion/Software/PC/FlexMotion/

[Jayson]

per motors. We are running into unexpected speed limitations with the motors. Increasing the speed and acceleration past a certain point (which is well below the motor's and motor driver's capabilities) makes no difference to our period of our cycle. Why?George,
I know the issue you are talking about. This is a known issue and there is actually a patch available to correct the problem you have been seeing. It is found at: ftp://ftp.ni.com/support/motion/Software/PC/FlexMotion/

The files you want to download are 5.01f1 patch and 5.01f2 patch. These are firmware files that you will be able to download to your board via Measurement and Automation Explorer. Readme files are included with each as well.

Jayson Wilkinson
Motion Product Manager