[sdavenport]

Hi Tom,

I was wondering if it would be possible to use Kflop in a PLC control scheme without any hardware connected to it. We have an X, Y gantry stone polishing machine. The machine has an HMI with many canned polishing patterns and works fine with straight moves. We would like to be able to odd shaped stone which would require coordinated moves. There is a Do-More PLC controlling 2 VFD motors with encoder feedback. The PLC is not capable of doing coordinated moves. I would like to send X,Y point(s) and velocity to the KFlop via modbus/ethernet. I would then stream encoder positions as fast as possible and get back velocities to pass on to the PLC's analog drive signal. The Kflop would only be used in automatic mode. Speeds are slow and accuracy is not critical. (+- .5 inches, ~2000 encoder counts). Do you think this is doable?

Thanks, Shannon

[TomKerekes]

Hi Shannon,

I think sending the servo input/output to/from KFLOP via Modbus might be too slow. Running Modbus at 56KBaud I would expect you could only maintain an update rate of ~50Hz. With a 50Hz Sample rate the servo response bandwidth might be only a few Hz.

The rest would probably be theoretically possible. Normally Trajectory Planning through a path is performed on the PC. But for relatively simple cases it can be computed within KFLOP. You might look at the Ellipse.c example added in Test Version 4.33k. It computes a table of points along an elliptical arc, then accelerates through a few points, runs at constant rate through some points, and finally decelerates through the last few points. That might be similar to your case as you can probably substitute the points in the table to form any smooth path.

Regards

[sdavenport]

Thank you Tom
I'll look for another solution on this one.
Shannon