How can I change the speed of a stepper motor?

[Draben]

HSI bipolar Linear Actuator Size14, HSI Chopper Driver 40105, NI PCI-6052E, NI SC-2345, 2 SCC-DO01 modules, and SCC-FT01

The motor works at one speed with a boolean array input, using the SCC-DO01.  But I need to be able to change the speed of the motor.  Specifically it needs to operate on several frequencies of functions of as displacement vs. time, such as sine wave, triangle wave, and square wave.  I tried to find information about using a digital pulse train but had no luck.  Is it even possible to accomplish with this hardware?

Message Edited by Draben on 01-22-2006 09:43 PM

[Jochen]

In general E-Series DAQ-boards like the PCI-6052E are not very good for motion control tasks. The 6052E doesn't provide hardware timed digital I/Os so you can control the digital lines only by software. This is both slow and inaccurate as long as you are running the board under a non-deterministic OS like Windows.

On a real-time OS the jitter would be better but still the frequency would be low and it would still be hard to program accurate acceleration and deceleration ramps.

If you use the counter/timer instead of the digital I/Os you could reach higher velocities and a much better timing accuracy but it would be even harder to program acceleration/deceleration ramps which you will need if you want to reach higher velocities with your stepper motor. Additionally for motion control applications you may want features like limit switch monitoring and following error tracking which require again real-time capabilities.

With this said I don't recommend the usage of a multifunction DAQ board as a motion control board. Please have a look at the NI motion control boards like the PCI-7332 which does all the motion I/O and trajectory control onboard.

Best regards,

Jochen Klier

National Instruments Germany