Scott, You got a lot of replies on a topic with a lot of fog surrounding it, but I need to chime in here so you don't repeat my mistake: I broke a motor coupling about a year ago during servo tuning. The sound almost scared the coolant out of me! I am no controls expert, but I now know why it happened. It was because I didn't model my own system before blindly tinkering with the ini file. Before doing anything I would advise knowing your Anilam servo amps. For example, my Yaskawa servo amps close a current loop internally, then have a velocity loop outside of that with adjustable P and I (via autotuning). EMC2 then closes the outermost position loop using only P and FF1. This is known as a P/PI Cascade Loop with Velocity Feed Forward. The I and D terms in my ini file remain at zero! It took a lot of reading outside of EMC2 documentation to cut through the fog, but it is now clear to me. There are several possible ways of nesting loops and combining control terms beside PID, so don't fall for the "add a little of this and then a little of that" approach.
Jim -----Original Message----- From: Scott Hasse [mailto:scott.ha...@gmail.com] Sent: Wednesday, August 17, 2011 2:32 PM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Mesa 5i23/7i33TA servo instability question I'm in the shop working on this right now and am wondering how to verify the PID loop is providing feedback to each axis. I've been using pncconf to generate the configuration, and assumed since it allows you to set PID that it would configure it to feedback automatically. However, since I've been using pncconf as a crutch, I'm not sure off-hand how to config PID feedback is working. I see P, I, D values in the ini file for each axis, but I am still seeing small amounts of servo instability. I see the instability even with the servo signal grounded. I have followed this page: http://wiki.linuxcnc.org/emcinfo.pl?Tuning_EMC2/HAL_PID_Loops and verified that the output voltages are correct, but get stumped at the: Set up PID loop add the loop and interconnect step. Thanks in advance for any advice, Scott On Wed, Aug 17, 2011 at 7:55 AM, John Thornton <bjt...@gmail.com> wrote: > The 1100M came both ways with glass scales (earlier model) then with > encoder feedback. Mine is the encoder variety of 1100M. > > John > > On 8/17/2011 7:28 AM, andy pugh wrote: > > On 17 August 2011 04:15, Scott Hasse<scott.ha...@gmail.com> wrote: > > > >> To the point, though, I am having one not-so-minor problem. When I > enable > >> the servos, they are not completely stable, and I'll get following error > >> almost immediately after enabling them. They don't run away, but the > >> encoders show them moving ever so slightly, and physically the motors > >> actually are moving. > > Are you retaining the velocity feedback to the amps, so that they run > > an internal velocity loop, and then you use velocity commands to close > > your position loop based on the encoders? > > > > The previous Anilam system I chatted to someone about had velocity > > tachs on the motors and linear scales, no rotary encoders. > > > > So, in Anilam control is the feedback from linear scales, and encoders > > in EMC2 mode? > > > > > ------------------------------------------------------------------------------ > Get a FREE DOWNLOAD! and learn more about uberSVN rich system, > user administration capabilities and model configuration. Take > the hassle out of deploying and managing Subversion and the > tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users This communication is for the use of the intended recipient only. It may contain information that is privileged and confidential. If you are not the intended recipient of this communication, the disclosure, copying, distribution or use hereof is prohibited. If you have received this communication in error, please advise me by return e-mail or by telephone and then delete it immediately. ------------------------------------------------------------------------------ Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
