Re: [CAD_CAM_EDM_DRO] EMC2 Servo Loop

Phil@Yahoo wrote:

> Yes, I get the idea. I just wonder what the main advantage is of having the
> servo loop run through the PC if not to reduce the external hardware. If you
> have to add external encoder counters it doesn't seem the cost would be much
> different from having a self-contained servo controller that simply takes
> step-direction commands and reports errors, etc. Cheap microcontrollers can
> easily handle that computing load.
>

If you already have a fully-debugged N-axis motion controller that does
everything you
want, then the EMC way doesn't buy you much. But, what if Joe in Idaho
wants to
change something, add a feature, whatever. With EMC2, everything is
available to him,
and can be easily debugged directly on the PC.
With some external box, then there is a second kind of machine code, and
cross-compiling
and cross-debugging tools, etc.

In great volume, little micros are really cheap, so it is quite
reasonable to use them.
But, look at what happened with Gecko Drives' G100 (GREX) product. It
was all of that, but they
NEVER got the firmware working to everybody's satisfaction. A good part
of that was related
to the cross-development tools that kept a wider range of parties from
helping.

Taking step commands from the PC is very limiting. With my hardware,
you can run the encoders
at well over 300,000 counts/second, and only send velocity commands to
the board. So, the
computer is reading position at some specific rate, and sending new
velocity commands out
at that rate, typically 1000 times a second.


Jon