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Stepper position control with myRIO
Riche29
07-09-2014 03:22 PM
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Hello,
I am developing a position control system to move a linear stage back and forth using a stepper motor (file 1). The stage will ultimately need to follow the motion path set out in a function that I have defined (file 2).
I have been able to get the motor to move using a Big Easy Driver from Sparkfun (file 3), sending it a PWM signal from one myRIO pin, and setting another pin on the myRIO to high or low in order to establish the direction. From what I understand, each low-to-high transition in the PWM signal causes the motor to take one step (or microstep). Therefore the PWM frequency is equal to steps/second, the motor speed. Using timed loops along with this information, I am able to control how many rotations the motor performs at a constant speed.
However, I would like to be able to count steps, so that I can give the motor a position (number of steps to take from some defined "home") and it will go there, and vary speed accordingly to get there and ultimately follow my function. I will apparently need to implement some sort of PID control eventually, in order to accomplish this task. Right now I would just like to know how I can keep track of the position of my motor and control it that way.
I greatly would greatly appreciate any advice on how to implement this process.
Best,
E
07-10-2014 04:16 PM
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Hi E,
How are you implementing PWM with the myRIO? Are you just using the myRIO express VI or are you writing your own code?
Also, just as a heads up, the Academic Hardawre Products page is a little more specific to the myRIO and is monitored by NI Developers who work with that device. If you post this question there, you may get a better response.
Product Manager, ATCA and BEEcube
National Instruments
07-11-2014 08:05 AM
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Hi Ryan,
I am using the myRIO express VI. I was thinking of a way to implement what I want if I was able to write my own code for the PWM, but as someone new to LabVIEW I wasn't totally sure how to go about doing that.
Also, thank you for the suggestion. I shall make the post on that page and discontinue it here.
E
