Re: [CAD_CAM_EDM_DRO] Re: breakout boards plus - hard choice

Quote: You could be right, the encoder was only for analysis of the
results, but that wasn't my memory of it.

You're right. He's using an encoder for feedback. Not part of the test, but the intended design. Because it was argued that it's just essentially the same as a servo from an application standpoint. Drive, motor and encoder.

If lousy yahoo didn't delete my archive, I could pull up the post. I have "mail plus" they announced one day I had unlimited storage, the next day it was empty. I guess thats what they meant...

Ron


Jon Elson <elson@...> wrote:
Mark Vaughan wrote:

> Hi Jon
>
> The G100 just has step direction output, and encoder inputs, it does have
> internal processing power, and it does command the step federate so it could
> detect and error and slow things down.

Sorry, I didn't mean to imply that a STOCK G100 would be part of
this unstallable stepper scheme. It may, in fact, be possible
to do it without adding hardware to the G100, Mariss hasn't been
totally clear on this because he doesn't want to reveal too much
before he has a product ready to go.
However when released the firmware

> with the G100 had many many fault, Mariss coped out saying he was not a
> programmer, so I very much doubt he has implement a closed loop himself
> within the G100. The guy that now develops the G100 firmware Stephen, is a
> good programmer, but he is generally very vocal when he gets a new trick
> running, and we haven't heard from him regarding this.
>

I am confident that Mariss did, indeed, make the unstallable
stepper work on his bench. That doesn't mean there were not
pieces of laboratory test gear still wired into the system, and
I know he was not controlling it with G-code or Mach(x). It was
entirely a lab demo, not a CNC machine tool, but I know Mariss'
style well enough to know that if he said "it worked", then
indeed it DID work!

> I am still fairly sure Mariss is looking at the current response to a pulse
> and from that determining impeding failure of a step so he knows when to cut
> back the feed rate and store pulse errors with his stepper card. It's been a
> long time since I studied steppers, but if memory serves me right as you
> load a stepper, the current lags and the crest factor changes, just before
> stalling there are massive crest factor changes.

All this should be in the archives of this list or the Gecko
list, I don't remember where the major discussion developed. At
speed, (and maybe that is the only place stalls should occur)
there should be enough back-EMF to know what is happening at the
motor. My concern was that at near-zero speed, there won't be
enough back-EMF to detect in the noisy environment of a stepper
drive, and so a stall could occur without being sensed. This
would require running the machine into an obstacle (a "crash")
but it is a situation that happens all the time in the shop.
You could be right, the encoder was only for analysis of the
results, but that wasn't my memory of it.

Jon





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