On Sunday 02 May 2021 21:02:29 Gene Heskett wrote: > On Sunday 02 May 2021 16:34:43 Jon Elson wrote: > > On 05/02/2021 01:00 PM, Chris Albertson wrote: > > > The below is exactly true. The problem is that PID is widely used > > > and PID is only "reactive" it can only deal with what has already > > > happened and the time lag is the source of oscillations. In the > > > past, PID was the only control option because we had limited > > > computing power. > > > > True for classic PID. The PID calculation in LinuxCNC also > > has feedforwards (FF0 - FF2) which > > are quite useful, as they give an approximation of the > > required drive to the motor without the output, move, sample > > delay. > > Yes, and that I have found usefull. But using them intelligently > isn't at all well explained by the docs we have. Time constants and > their effects are are not at all well explained. The bottom line is > that if and when you hit the magic settings, you still have no idea > why this works and that doesn't. > More specifically, which of the F's is suitable for forcing a closer to null settling point when there is considerable friction in the system? Something that will see it sitting at 3% power constantly, and will raise the gain enough to move it another arc-second for a more perfect null. Best applied where a pwmgen is operating in mode 2 to drive an H bridge. I've considered adding a high frequency jitter to the control so that friction might be overcome, but that needs to be controlable, something that as long as the error exists, will raise the amplitude of the jitter until it does move. Something that looks at the encoder to detect movement that should reset the accumulated jitter amplitude to start a new cycle when the encoder says it has moved for instance.
See what happens when I let my imagination out to play at 4 am without a chaperone? > > Jon > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > Cheers, Gene Heskett Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
