Greets - I have a press brake I am working on rebuilding; eventually we
will be converting it over and using LCNC to fully control the system,
however due to request, I am going to [try] using LCNC only as the
graphical front end to send commands to the existing Yaskawa SMC-2000
motion controller. (The press's original Win95 pc has failed after a
number of extended rebuilds over time.)
The SMC 2000 takes commands over a serial port (typically a 2 letter
command with a couple parameters) and the command protocol is well
documented. For my purposes, the most common command will be "move axis
n to position xxx.xxx with feedrate yyy.yyy and stop", of which the SMC
2000 will take care of without further intervention.
I have used serial port devices in userspace in prior works (typically
PIC or atmel microcontroller low-speed interfacing) that doesn't require
any realtime priority.
The sending of a command also isn't a high realtime priority as with a
pressbrake, there really isn't co-ordinated axis motion like with a
cartesian machine. (Life is much slower with a press brake).
My concern is with the readback of the position data. I'd like to use
the SMC-2000's position variables and feed them into Axis' DRO
(preferably right into axis.n.motor-pos-fb) however it would be at a
relatively slow rate - perhaps 2-5 times per second. With an update rate
so slow, I expect my (virtual) following error will become huge and
cause a fault. The actual following error doesn't exist, just the
perceived deviation between DRO updates.
Any recommendations on getting around that problem? Just a huge
following error allowance, or is there a cleaner method to omit EMCMOT
or certain other components to simply accept a motion command from axis,
and accept an occasional position feedback? I will be washing the
position command through a custom userspace component to translate the
command into a proper string for the SMC 2000, as well as convert the
feedback value to something Axis can use. Both the command and feedback
update rates will be at the mercy of the userspace update loop of course.
The SMC2000 controls feedrate, as well as has its own interlock and
e-stop loops for safety.
If anyone has used an SMC 2000/4000 platform before, I'd certainly
appreciate any advice that comes my way.
Regards,
Ted.
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