Chris Radek wrote:
> On Sun, Jul 11, 2010 at 12:11:55PM +0300, Alex Joni wrote:
>
>
>> Maybe you can use halui.machine-is-off
>>
>
> I think that's a bad approach because halui doesn't give status in
> realtime.
>
> If you want the user to still be able to go to machine-off manually,
> I guess you can't use the falling edge of axis.N.amp-enable-out to
> trigger estop.
>
It would be OK if the only way to get to that in-between state ("machine
off") was
by hitting F1, and then after going to "machine on" if you hit F2 it
would not
only go the "machine off" but E-stop also. I will have to try this.
> The only other approach I can see is to monitor axis.N.ferrored
> directly. Beware ferrored is only true for the one servo cycle
> where the ferror is detected.
>
>
This requires ORing all the ferrored signals together, might be more
complicated,
but if the amp-enable-out requires an edge-detection function, it might
work out
about the same.
> If I understand right you asked this because you wanted braking at
> ferror. Is there some reason to not have braking whenever machine is
> off? Seems like you could hook the braking system to amp-enable-out
> directly (unless the machine is moved with handwheels or something?)
>
No, it is not braking, exactly. When in "machine off" the positioning
loop is off, and the velocity
DACs send as close to zero Volts as they can. The servo amps drift VERY
slowly, but this
can still be a problem. For instance, if I have a following error when
a tap or drill bit is
at the bottom of a hole, the X and Y axes will creep, and if I don't
remember to hit E-stop
immediately, it will break the tool off in the hole. I use the Estop
signal to enable/disable
the servo amps. So, when I hit F1, the servo amps are powered up and
enabled. There is
a pretty big transient as the amps go from open-loop to closed-loop
operation. This settles
out in 50 ms or so. Then I can hit F2 and the positioning loop is
enabled in EMC, with no
outside disturbance, and the machine begins holding position with a
tight following error
tolerance. Although I have not tried it, I suspect if I tied the enable
of the amps to amp-enable-out
that the closed-loop transient of the servo amps would cause a following
error, and you'd never
be able to bring the system online.
So, I think I need this two-step process to allow the servo amps to
stabilize before going to
"machine on" (I have this, now) , and I'd like to also make it go to
E-stop whenever there is a following
error. I still need to decide which of these schemes is the better one
(amp-enable-out or ferrored).
Thanks,
Jon
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