On Wed, 2 Feb 2011 21:08:09 -0800 (PST)
"Peter C. Wallace" <[email protected]> wrote:

> It was pretty surprising. I was using Matt Shavers velocity mode test
> hal file with halrun, so the effect was not masked by a FE as it
> would be under EMC. If we had any integral gain and put enough load
> on the motor that it could not match the requested velocity, and
> therefore saturated the PID output, as soon as we removed the load,
> instead of a velocty overshoot and recovery, the PID loop locked up
> with a saturated output resulting in a runaway.

We had some motor runaway during a test this morning. I wasn't
physically present when it happened, but the fellow doing the testing
said that as soon as the "8i20.enable" box was checked in the Pyvcp
GUI, the PID output would latch at 1.0. Interestingly, I believe
pid.0.enable was set to false (which should reset the integrator), but
upon re-enabling, the output once again latched at 1.0. I don't know
what the pid output was when pid.0.enable was false. A restart of halrun
allowed the testing to continue with no changes in the config files.

I looked at pid.c, but I don't know enough to mess around in there :)

Test files are at:
http://www.mattshaver.com/8i20/

Thanks,
Matt

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