On Wednesday, May 09, 2012 01:28:26 AM andy pugh did opine: > On 8 May 2012 22:37, gene heskett <[email protected]> wrote: > > On Tuesday, May 08, 2012 05:34:22 PM Peter C. Wallace did opine: > > > > From the pid man page: > > pid.N.FF0 float rw > > Zero order feed-forward term. Produces a contribution to > > the output that is FF0 multiplied by the commanded value. > > ... > > > Multiplied. That sound like I'd need a gain reduction term, > > Yes, just use a value less than 1. > > In answer to a previous question, here is a summary of PID without any > maths that I wrote: > http://www.linuxcnc.org/index.php/english/component/kunena/?func=view&id > =14483&catid=10#14487
Somebody said they had a Pgain of 60, so I reset FF0 to .1 and tried that. The gain was so high just tapping the clockwise button ran it up to 1100 revs. So I put it back down to 6.0, then played with scale gains in pwmgen and that worked, a bit soft, but blocking the chuck at about .5 rps made it clear the fuse in about 3/4 second, so it was definitely working. So I tried to cut a thread, not too well it appears. It looks as if my encoder wheel has 2 or 3 fairly large cyclic speed variations as there is a pattern of narrow and wide threads in the final product. Watching the encoder on my scope, it looks very consistent, but the encoder.0.velocity output has wibbles of +-50% in its speed, and applying the lowpass with a gain of .01 takes a long time to settle to near zero when the spindle is stopped, in excess of 10 seconds, but the displayed value out of the lowpass still has these 50% wibbles at thread cutting speed, and even at 1100 rpms, the displayed value still has a 20% noise in it, all the way from 17 to 21 RPS being displayed, and I believe that is whats driving the Z so inconsistently that I can see it in the finished thread. Or at least that is my theory. And I'm thinking G76 itself may have a problem in the q area. It made a thread as if q was set to double what it was, which is Q29.5. Could the G7/G8 switch affect that? Late, getting sleepy in WV. Thanks Andy. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> I knew one thing: as soon as anyone said you didn't need a gun, you'd better take one along that worked. -- Raymond Chandler ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
