MAX does not run stepper motor

[PKP]

I am an abosolute novice at NI Motion and cannot get MAX to move a stepper motor. I'd be very grateful for any help.

The system consists of a PXI-7340 Motion Controller card installed in a PXIe-1065 chassis. The PXI-7340 is connected by means of a SHC-68-C68-S cable via the Motion I/O port to the Motion I/O port of an UMI-7774 board. The UMI-7774 board is supplied with a 24Vdc power supply as well as an isolated 15Vdc power supply to its power terminals. Two stepper motors are to be controlled using this UMI, which has 4-axes capability. The Axis 1 and Axis 2 sections on the UMI are connected to a Danaher Motion P70530 Stepper Drive each by means of a D-Sub to D-Sub cable via the Control port on the UMI and the J4 Command port on the P70530 Drives. The P70530 drives are supplied with 65Vdc power from a bench top DC power supply capable of 70V, 15A. Each P70530 drive is connected to a Pacific Scientific Powerpac stepper motor (N33HRHJ, 65V, 5A).  (Thus, two P70530 drives and two stepper motors are connected tothe UMI.)

I am trying to get MAX to turn the motor. In the listing in MAX, under NI Motion Devices/PXI-7340/Default 7340 Settings/Axes 1/Axes Configuration, all limits were disabled, settings saved and initialized.

However, in the 1-D Interactive window, when the Target Position is set to a value, e.g. 2000 steps, and the Start button is pressed, the motor does not move.

But, the LED on the P70530 blinks until the Kill button on MAX is pressed.

Can anyone tell me why the motor does not move?

Where does one go to learn more on MAX? Why are all the manuals at NI made for experts who already know what they are doing and not for beginners? The Help is no help at all really.

Regards,

PKP

[jpaul]

Hi PKP,

A good introduction to NI Motion can be found in the following NI Developer Zone article:

Fundamentals of Motion Control

 ** Note there are more basic MAX configuration App Notes in the Software for Configuration, Prototyping, Development section of this article **

You can also enable the help pane for MAX which provides you with information on the MAX selection that you currently have highlighted (Enable by going to View >> Help Pane).

Hopefully these documents help to point you in the right direction and let me know if you have any further questions/clarifications.

Cheers,

Message Edited by jpaul on 03-03-2009 03:52 PM

[PKP]

Thank you, Jonas, for your reply.

I called in to NI and talked with "Vivek" and he helped me set the MAX settings and the DIP switches on the P70530 motor drive (amplifier) to get the motor to run. He pointed me to the "Getting Started P7000 Series Stepper Drives" 28 page manual, which for some reason was not included in the CDROM that came with the P70530 drive or with the pre-installed manuals in the PXI chassis. (You would think to include all the relevant manuals on the CDROM, but nope.) The manual showed how to "Change Settings" for the PXI-7340 inside MAX and set it to the 7340 Settings for P7000 Drives.

Under Axis 1/Axis Configuration/ Stepper Settings tab, set the Stepper steps per revolution to 5000.

Under Axis 1/Motion I/O Settings, all the filters, switches and the "Inhibit Output Settings" has to be disabled.

Now the motor runs. Yay!

But there is one teeny-weeny thing.

Under  Interactive/1-D Interactive, when the velocity is set to 100 rpm or more, or the Acceleration is set to over 20 rps/s, the motor whines and does not rotate.

When V=0 to 95 rpm, Acc=10 rps/s, the motor runs for a given Target position value (such as 200, 2000, 20000, etc.)

Here is another weird observation. When the Velocity is set to say 60 rpm, the actual motor speed measured with a tachometer and a stroboscope is found to be  about 1440 rpm, i.e., 60 x 24 rpm. (I measured the rpm using the two different devices and both tend to agree.)

Is the "rpm" unit a typo? Should it be something else?

What am I missing? Why is the stated rpm different from the actual measured rpm?

Thanks for any help.

Regards,

PKP

[Brian_Beal]

It sounds like your amplifier is set for full stepping(200 steps/rev), not microstepping.  5000/200=25.  You will need to match the microstep setting on the drive with the "Steps per revolution" setting in MAX.  If you don't know how to change it on your drive, then change the MAX setting to 200. 

[PKP]

Thanks, Brian. I changed the stepping to 200 steps/revolution and the speed seems to follow the enterred value. Now things are starting to make sense.

I tested the motor at a higher rpm (up to 3000 rpm) over its rated 1500 rpm. Is that okay?

Thanks once again to everyone.

PKP

[Buechsenschuetz]

Operating a stepper motor with rpm values higher than the ones rated usually does not cause any damage, but torque may decrease significantly. So it is NOT adviseable to run a stepper motor beyond its rated value in a real system, although this is possible for tests.