Does Waveform Data and Motors Play Well?

[1eyedjack]

Hi

I am writing a vi that controls two stepper motors, and am looking to be able rotate one at a constant velocity, and rotate the other's velocity in a sinewave pattern. 

Equipment:

2 Stepper Motors (CTP12ELF10MAA00)

2 Encoders

MID-7604 Drive Box

PCI-7330 motion controller

The constant rotation seems to be working well, althought sometimes I run into an issue that the actual velocity is less than the velocity i'm inputing to the motor (by around 10 RPM).

Where I'm having an issue is sending data to move it in a sine wave pattern. I've tried a few different ways to send the data, through sine vi, sine express vi,... but the motor doesn't vary in velocity. It seems to just choose some velocity within the sine pattern its given and run at this velocity constantly. 

I saw a previous post, back from a few years ago which is similar to my question as well, but it was never answered: http://forums.ni.com/t5/Motion-Control-and-Motor-Drives/stepper-speed-changing-in-a-Sine-waveform/m-...

I'm fairly new to labVIEW with just a few basic programs under my belt.

Thank you for any help you can offer,

Arthur J.

[Tim_O1]

Hi Arthur,

Take a look at the example below and see if it works on your system. I think it is doing exactly what you are looking for.

Sequence of One-Axis Velocity Moves
https://decibel.ni.com/content/docs/DOC-4744

Tim O

[1eyedjack]

Thanks for that link. Looks pretty good, I'm going to try to integrate it tomorrow.
I'll let you know how it goes. 

[1eyedjack]

Is there a way to integrate this into an event structure? It seems to require the while loop running continuously, or is that just for the 'read current velocity' portion?

For example what if after a certain amount of time you wanted the amplitude of the sine wave to change? 

[Tim_O1]

Hi Arthur,

The example has an array of values that represents what speed the motor should run at. The inner while loop reads the current velocity and waits 1000ms(which allows the motor to run at that set speed for one second) and then the outer while loop will pull the next velocity value from the array and then call the inner loop and so forth.

There are multiple ways to implement what you are looking for. A quick way using this examples would be edit the inner while loop to have a wait of 5ms and have a button wired up to the “Stop if True”, so that you continue to run at a set velocity until the user presses the button, which will load up the next velocity value from the array. Or instead of a button just write some logic to wait a certain amount of time before loading the next value.

You could write your own logic and event structures if you want. All you need to do is follow this example. So any time you want to change the velocity, you will need to load in your target velocity into the Load Velocity RPM.flx and then call Start Motion.flx.

Tim O