Re: Close loop steppers
Posted by
beer@x...
on 2000-01-17 09:56:50 UTC
On 17 Jan, CAD_CAM_EDM_DRO@onelist.com wrote:
it's either because it's not powerful enough or the feed rate is too
high.
Having said that, I started a software project - currently shelved -
that was a combination DRO/stepper feedback system.
The idea was this. The little box was fundamentally a DRO. The box
also had step and direction inputs AND step and direction OUTPUTS and
is connected between a PC running CNC software and the motor controller.
When a step pulse came in, a step pulse was immediately issued. The
box then watched the DRO to see if movement resulted. If there was no
movement ( as indicated by the DRO ), the CNC software was paused and
additional steps were issued by the little box until suitable movement
DID occur. The pause line was released and normal operation continued.
This requires that the CNC software have a "pause" input, as opposed to
an EStop input. ( Doug Yeager of CNCPro did add such a feature, BTW.)
My idea when designing this system was not missing steps, but instead
was meant to be a poor man's ball screw replacement - automatic backlash
compensation and worn leadscrew compensation. ( NOTE: I did not intend
this system to be a linearizer for cheap leadscrews, although it could
be used as such, with sufficient programming time ) Still, it would
also work as a missing step "fixer".
Before actually implementing this system, an opportunity arose to
convert my machine to ball screws, and so the system will be DRO only,
at least for a time.
Alan
--
Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta
> Message: 5I don't think a "proper" stepper system should lose steps. If it does,
> Date: Sun, 16 Jan 2000 09:06:33 -0600
> From: Les Watts <leswatts@...>
> Subject: Re: Close loop steppers
> I think the simplest stable control system would be to add missing steps during
> the next rapid or other noncutting portion of the cycle. An all axes off command
> would be issued if any axis exceeded a certain error.I think for each stepper
> I need several bits of digital I/O and a timer counter channel. I don't want to
> reinvent the wheel at this point. Does anyone have software that does this
> already?
it's either because it's not powerful enough or the feed rate is too
high.
Having said that, I started a software project - currently shelved -
that was a combination DRO/stepper feedback system.
The idea was this. The little box was fundamentally a DRO. The box
also had step and direction inputs AND step and direction OUTPUTS and
is connected between a PC running CNC software and the motor controller.
When a step pulse came in, a step pulse was immediately issued. The
box then watched the DRO to see if movement resulted. If there was no
movement ( as indicated by the DRO ), the CNC software was paused and
additional steps were issued by the little box until suitable movement
DID occur. The pause line was released and normal operation continued.
This requires that the CNC software have a "pause" input, as opposed to
an EStop input. ( Doug Yeager of CNCPro did add such a feature, BTW.)
My idea when designing this system was not missing steps, but instead
was meant to be a poor man's ball screw replacement - automatic backlash
compensation and worn leadscrew compensation. ( NOTE: I did not intend
this system to be a linearizer for cheap leadscrews, although it could
be used as such, with sufficient programming time ) Still, it would
also work as a missing step "fixer".
Before actually implementing this system, an opportunity arose to
convert my machine to ball screws, and so the system will be DRO only,
at least for a time.
Alan
--
Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta