MODBUS parameters for VFD communication to Labview

[RavensFan]

Great!   I'm glad to hear that.  It always feels good when the effort pays off like that.

[belae1ka]

It's an incredible feeling!!! Thank you so much!!

By the way I have another question I was hoping you (or Dave) may be able to assist me with...

As you may or may not know, the project I am working on is to design the control system for a shock dynamometer. The shock dyno will look a little something like this;

So one of the main objectives in my project is to produce a plot as seen below;

The force will be data coming from a load cell.

The Displacement will be the linear displacement of the shock being tested (the compression/rebound). To clarify what I mean, I have included the figure below;

My question is: Do you think I would be able to acquire the shaft position from my motor using my VFD? 

I called AutomationDirect (the manufacturer of the VFD) and asked them this question and they told me no considering the motor I am using (3 phase) is not a servo motor but I just wanted to double check with the forums to make sure. I tried reading the encoder feedback registers through Modbus and moving the shaft by hand to see if any values changed but no luck. I'm guessing I may have to implement some kind of proximity sensor in order to acquire the data for displacement. Due to the design of the dyno, I don't think I would be able to attach an external rotary encoder to the shaft of the motor. Any suggestions?

Thank you.

-Kevin

[RavensFan]

Is that gearbox a speed reducer or speed increaser?  (I'm guessing speed reducer.)

I don't see why you physically couldn't put an encoder on the motor shaft, but if it is a speed reducer, then it would take multiple revolutions of the motor to get 1 revolution of the cam actuator.  You could never resolve where in the cam rotation you are.

But couldn't you put the encoder on the cam actuator shaft?

A proximity sensor watching the moving slide could certainly get the position.  Read that continuously and you'd have a sine wave.  Where you are in the sine wave will tell you the angular position of the actuator cam.

Even if you could get the data from the motor, you'd have a hard time correlating the position there with the other data you'd be collecting.  Serial communication has inherent delays.  By the time you requested and got back the motor data, it would be stale.  You wouldn't know precisely when it occurred.

[belae1ka]

Thank you RavensFan, 

I believe Implementing a proximity sensor would be the most logical option.

How would I go about plotting force vs distance?

To clarrify...My proximity sensor moves up and down a total of 2 inches. I would like to plot the force output of the load cell at any given distance that the proximity sensor reads. For example, The x axis would go from 0 to 2 inches and I would like to plot the force every .1 inches. The y axis would be the force.

Thank you.

[belae1ka]

Note: i would like to plot the force output at the exact same moment that the corresponding distance is read at. Would i need to implement a time stamp?

[awgw96]

Hi belae1ka,

If you still have the VI you made to control the VFD, would you be able to post it here? I am also trying to control a VFD through labview and am having issues, so your VI will be helpful.

Thanks,

Andrew

[Tamir87]

can you please share your code?