Controlling two Stepper Motors Simultaneously

[malkoba]

Hi

I am using Labview 7.1 with NI motion control. I am driving a stepper motor using NI PCI 7334 and the MID 7604 driver.

I have already got one stepper motor  to run intermittantly with a regular interval between steps as per the attached programme. I wish to modify this programme to run two such motors in synchronism to each other. I would appreciate if someone can help me on this. At present the motor  runs clockwise (seen from the shaft face of the motor). How can I get it to run anti clockwise. Is there any setting for this in the MID 7604.

Thanks

Mal

[Jochen]

Mal,

could you please explain a bit more in detail what exactly you are planning to do?
The vi that you have attached runs an untimed loop (which by the way causes 100% CPU load...), moving the motor by one step in each iteration (depending on your calculations). This is completely undeterministic behavior and I'm sure that you don't see smooth moves. This way the velocity of your motor is just related to the speed of your PC and has literally nothing to do with the frequencies of the waveforms that you have calculated before.

In fact you don't really use the board's motion capabilities. Why don't you let the board generate the steps by it's own?
Just to answer your question: You can change the motors direction by providing a negative target position but I don't think that this is the most important question that you should have.

Please give me a better idea what you want to do because it really looks like that your current approach won't bring you the results that you are looking for.

Best regards,

Jochen Klier
National Instruments Germany

[malkoba]

Hi

Thanks. My requirement is to move rotate two stepper motor simultaneouly. I require to rotate them a user selectable angle (say about10 degrees) and then stay idle for a user selectable duration ( say about a minuite). Then rotate another 10 degrees and stay idle for a minuite and so forth till it is switched off.

My concern is about the torque and not the velocity. I would appreciate your help and advice on this.

Thanks

Mal

[Jochen]

Mal,

before you start with programming please examine the motion control examples in your LabVIEW folder to learn how to use the NI-Motion vis. The motion control board can generate the step sequences by it's own so you don't need to try to rebuild this feature in your software.

For your application you should use the appropriate vis to load values for acceleration/deceleration, velocity and target position. Especially as you are concerned about torque you should adjust the values for acceleration/deceleration appropriately. Then start the move, wait until it is completed and use the Elapsed Time express vi to wait until the next move should be started without blocking the main loop in your vi.

Please note that the torque of stepper motors is physically limited. If you need to compensate dynamic torque changes you should better use servo motors.

Jochen

Message Edited by Jochen on 10-02-2006 11:25 AM

[malkoba]

Hi

Thanks for the advice. I ll try and post for clarification.

Thanks

Mal