non-linear motor velocity command

[swsyoon]

Hello, I'm trying to control step motor and I have driver from Applied
motion,inc, which is PDO5580 and STAC6-Q.
I'm wondering if I can control step motor with velocity command of function of time
using NI motion control card and software. Also, I need voltage input to change
the step motor direction back and forth using some function.

It would be very appreciated if you recommend the card and software.

The velocity command, For example, is V= 2 * exp(0.05*t), where t = time.
The step motor is a part of linear actuator and the attached is example for motion of linear actuator

Thank you

Wonseok Yoon

[Jochen]

Wonseok Yoon,

the NI 7340 and NI 7350 motion control boards support contouring mode. This mode allows you to generate arbitrary velocity profiles by calculating position vs. time arrays.
In order to calculate the contouring data for your application, you will have to integrate your equation in a 10 or 20 ms interval.

Please click here and here to learn more about contouring and other features of NI motion devices.

Could you please explain a bit more in detail what you mean with this sentence: "Also, I need voltage input to change
the step motor direction back and forth using some function."?

Thanks,

Jochen Klier
National Instruments

[Brian_Beal]

The STAC6-Q  is a fully programmable motion controller.  If you have a DAQ card with analog output, you can use the joystick function of the STAC6.  Your velocity profile can be generated using DAQmx, and the STAC6 would follow the speed.  As an alternative, you can use the serial interface of the STAC6 and send it velocity commands at predetermined intervals.  I recall that I could query the STAC6 serially over 100 times/second.  That should be good enough for what you are doing.

[swsyoon]

Thank you for your kind reply.

By the analog voltage input I mean, is if the analog voltage goes down to zero(not exactly zero), then I will turn the motor motion in opposite direction.

I need analog data acquisition port too. Does the motion controller card has analog singal input?

So, rotaional direction of motor is supposed to change depending on the value of analog signal.

I appreciated your help.

Wonseok.

[Jochen]

Wonseok,

I don't know the drive that you are using, but Brian's suggestion also sounds like a valid option. The 73xx boards provide analog inputs but they are not meant to be used as very accurate measurement inputs and they can't sample very quickly, too. So a DAQ device would like the PCI-6221 would be recommended anyway. This device would also allow you to generate the analog output signal that should be proportional to your velocity profile.

Still I have some concerns about your timing needs. Regardless if you are using a DAQ board or a motion control board in contouring mode, the control signal will always be generated in a hardware timed, buffered way. That means, that there will always be some significant delay (probably at least 10 ms) between the detection of the low level of the input signal and the direction change. If this is a problem for your application, you will have to switch to a single-point mode. That means, that in one cycle you have to read the necessary inputs, do your calculations and update the necessary outputs. Only one read and write operation per channel and loop cycle.
This will allow you to react very quickly to external events, but it typically requires a real-time OS, as Windows doesn't provide clean timing.

Regards,

Jochen