On Thu, 3 Feb 2011, Matt Shaver wrote: > Date: Thu, 3 Feb 2011 13:18:03 -0500 > From: Matt Shaver <m...@mattshaver.com> > Reply-To: EMC developers <emc-developers@lists.sourceforge.net> > To: emc-developers@lists.sourceforge.net > Cc: d...@smithy.com > Subject: Re: [Emc-developers] pid bug > > On Wed, 2 Feb 2011 21:08:09 -0800 (PST) > "Peter C. Wallace" <p...@mesanet.com> 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.
OK the first thing thats needed is to connect pid.n.enable to bldc.0.init-done so the integrator does not wind up during motor initialization. You can work around the PID runaway problem by setting pid.n.maxerrorI to pid.n.maxoutput/Igain. To fix the PID loop you need to remove these lines: (untested) 299 /* if output is in limit, don't let integrator wind up */ 300 if ( ( tmp1 * pid->limit_state ) <= 0.0 ) > > 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 > > ------------------------------------------------------------------------------ > Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! > Finally, a world-class log management solution at an even better price-free! > Download using promo code Free_Logger_4_Dev2Dev. Offer expires > February 28th, so secure your free ArcSight Logger TODAY! > http://p.sf.net/sfu/arcsight-sfd2d > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! Finally, a world-class log management solution at an even better price-free! Download using promo code Free_Logger_4_Dev2Dev. Offer expires February 28th, so secure your free ArcSight Logger TODAY! http://p.sf.net/sfu/arcsight-sfd2d _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
