Stepper Axis Encoder Problems

[rajpr00]

I have a NI 7344 board controlling a servo motor and stepper motor each with their own seperate drives. I am having issues with the stepper encoder output while running in closed-loop mode. When running the stepper in velocity mode the measured velocity according to the motion card is about 15% of what the actual velocity of the stepper.

The encoder position counts however, do update at the correct rate. If I connect the same encoder output to another axis and set that as a servo axis the encoder velocity is measured correctly (I've done it simulataneously and the servo axis displays the correct velocity while the stepper axis does not). I have verified that the stepper and encoder counts per revolution are correct and every relevant encoder setting is correct.

Anybody have any ideas?

Thanks

[rajpr00]

I upgraded NI-Motion and MAX to the newest versions and updated the cards firmware as well.
Once I reset the configuration back to its default and started from scratch it all seems to work correctly now.

On a seperate note though, I noticed I lost the ability to specify the primary and secondary input and feedback channels on each axis. I don't think I'll end up needing that functionality but it seems weird that the option is no longer available.

[MarcoPolo5]

The velocity reporting for steppers in NI-Motion 6.1.2 can be slightly incorrect at low step speeds with 733x and 734x boards because of a fixed point calculation error - this is ONLY a reporting error and the steppers WILL move at the correct speed. This has been fixed with NI-Motion 7.0.

The Primary and Secondary feedback channels can no longer be set in MAX starting with NI-Motion 7.0, however, they can be set through the Motion API in LabVIEW, CVI, etc. This change was made to reduce the complexity of the interface in MAX.

Hopefully this explains better the behavior of what you were seeing.