Re: Re: Andy Olney's Comments on PIC-Servo

----- Original Message -----
From: Matt Shaver <mshaver@...>
To: <CAD_CAM_EDM_DRO@onelist.com>
Sent: Monday, July 19, 1999 12:12 AM
Subject: [CAD_CAM_EDM_DRO] Re: Andy Olney's Comments on PIC-Servo


> From: "Matt Shaver" <mshaver@...>
>
> > From: "Andy Olney" <aolney@...>
> > I am guessing you
> > would want to access the serial port through the RTLinux subsystem to be
> > sure of communicating in a timely manner.
>
> A starting point for doing this is:
>
> http://www-public.rz.uni-duesseldorf.de/~jochen/computer/software/rt_com/
>
> > I am interested in the Pic Servo because is looks to be a cost effective
> way
> > to add closed loop motion control to my mill.
>
> Some observations about the marriage of the EMC to the PIC-Servo system:
>
> 1. If I understand correctly, the Pic-Servo boards do the servo control
> themselves and you feed them position commands. I have two reservations
about
> this:
>
> A. You are wasting a lot of the EMC's capabilities.
>
> B. How are multiaxis moves coordinated?

My impression is that EMC would issue a stream of coordinated position
commands.

>
> 2. If you want closed loop control there are a couple other ways to go
that
> might be easier (and just as cheap) than using the PIC-Servo boards:
>
> A. If you don't yet have motors, go with steppers and add encoder
feedback.
> This could be accomplished by interfacing the encoders to the EMC via Tom
&
> Dan's DRO board. Making this work with the EMC is something that would be
> useful in a wide variety of applications.

I actually have stepper motors with encoders that are being fooled by a
variant of the Pic Servo into acting as DC brushless motors. Switching to a
straight stepper system would be easy. ( not to mention the instant
gratification of a working system!)