On Friday 25 March 2016 15:46:41 Peter C. Wallace wrote:
> On Fri, 25 Mar 2016, Sebastian Kuzminsky wrote:
> > Date: Fri, 25 Mar 2016 13:35:46 -0600
> > From: Sebastian Kuzminsky <s...@highlab.com>
> > Reply-To: "Enhanced Machine Controller (EMC)"
> > <emc-users@lists.sourceforge.net>
> > To: "Enhanced Machine Controller (EMC)"
> > <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Encoder
> > failure
> >
> > On 03/25/2016 01:26 PM, Nicklas Karlsson wrote:
> >> As someone mentioned before a the an axis/joint may/will run away
> >> in case of an encoder failure.
> >>
> >> It would be possible to detect an encoder failure by comparing
> >> output signal with encoder signal. A velocity signal may be
> >> integrated and do not allow to wander to much or an encoder error
> >> will be detected. A torque signal would be worse.
> >
> > An encoder that fails into runaway (motion erroneously detected when
> > none is occurring) or that fails into stop (no motion detected when
> > motion *is* occurring) will both result in a following error,
> > precisely for the reason you say above: linuxcnc compares the
> > commanded position with the feedback position from the encoder.
>
> One type of encoder failure that is not detected by the following
> error is runaway when static.
>
> This is typically not as much of a problem with velocity mode drives
> since the commanded velocity is 0 so its more of a creep-away problem.
>
> But for torque mode drives, a broken encoder when static can result in
> a residual error being integrated up to full torque and resulting in a
> full speed runaway. This can be detected by looking at the PID
> saturated pin and faulting if set for too many successive samples.
Can you post a sample hal snippet for that?
> Peter Wallace
> Mesa Electronics
Thanks Peter.
>
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