> -----Original Message----- > From: Gene Heskett [mailto:[email protected]] > Sent: Monday, December 17, 2012 10:14 PM > To: [email protected] > Subject: Re: [Emc-developers] Servo Q > > On Monday 17 December 2012 21:12:02 andy pugh did opine: > > > On 17 December 2012 23:39, Gene Heskett <[email protected]> wrote: > > > I am at my wits end with this controller, and am now > ready to throw > > > more money at it. > > > > What is the problem? What are you trying to achieve? > > Stable, suitably stiff control where if I ask it for 5 rps I > get 4 to 6, 10 > rps gets me 9 to 11, 15 rps gets me about 15, and 20 should > be about tapped > out when the head gear is in low range. >
<snip> > I could probably stabilize it much better if the feedback gain was a > straight line near unity, and the compression to bend the > straight line > motion-rps out to compensate for the near exponential rise in > gain in the > motor circuit was in the path to pid.0.command. > > Humm, this gives me yet another idea to try. Send the velocity to > feedback, but drive pid.0.command like this: > > net src.cmd motion-out-rps>>scale>>invert>>mult2(both ins)>>sum2.0.in0 > | > > --------------------------------->sum2.0.in1 > > sum2.out>pid.command > > Then I could use the scale and scale offset to control how > much compression > was exerted to turn down the pid.command input at the higher speeds. > > Whether that would stabilize the P and I gain is TBD. At least I am > assuming that sum2 can subtract the increasingly negative output of > mult2.in0 as the requested speed rises. > > another equally nasty thought, clip out all the filtering, > both in the C41 > and in the JT250's pot arm circuit, go back to PWM mode in > pwmgen and just > bang the JT250 with the pwmgen output. But I've no clue how > fast the optos > are in the JT250, and the opamps they drive aren't megahertz > speed daemons > either. > > But its a thought. > > Cheers, Gene Gene, Are you using any FF1 in your PID? This should provide the major part of the output before any feedback action is required. Steve Stallings ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
