On Tue, 6 Oct 2015, Gene Heskett wrote: > Date: Tue, 6 Oct 2015 16:44:41 -0400 > From: Gene Heskett <ghesk...@wdtv.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: emc-users@lists.sourceforge.net > Subject: [Emc-users] joint following errors by the kiloton > > Greetings all; > > I gave up on that crashomatic box, and went out and found me one of those > Dell 745's with an Intel dual core running at 2.6GHz, and 4Gigs of > DDR-2. But I couldn't move that drive, no PATA connectors on the > mainboard. So I had to install fresh, which went rather swimmingly, > taking perhaps a half hour after I'd put my only new SATA drive in it, a > 2 Terrabyte Seagate I had more or less reserved for amanda's useage. > > I of course installed some of my personal pets, like mc, sshfs, unclutter > and synaptic. > > I let the package manager update aroun 350 packages including switching > our repo to master-rt, and about mid-morning there was another update to > the 2.8.0pre, which I automatically installed. > > But at that point I was still hacking up low profile brackets for the > 5i25 and its p2 breakout. > > Getting that going, I was amazed that there was not a /home/gene/linuxcnc > directory made by the installer! Is that a bug, or is that a function > of running pncconf the first time? > > I got sshfs working, and copied the 5i25.zip over to the new box, > unpacked that and installed the 2 files my 5i25 card needed. > > And installed boot.ko, needed to start Jon's pwm servo amp. > > And convinced amanda I needed to recover my /home/gene/linuxcnc tree so I > had all my configs and gcode back. > > And I've been the last 4 hours trying to get the machine to succesfully > home. I don't care how slow you set the speeds in the trajectory or > axis# sections, it will throw a joint following error, either while > cruising along at 10 IPM (last week it could move 70 IPM except for Z & > it could do 45!) or in making the stop when a home switch has been hit. > Its also moving some faster than any setting in the .ini file. > > Somewhere along the line it WILL throw a joint following error. On axis > X, or axis Z. > > Latency test has been run, and the servo-thread jitter is about 40 > microseconds. isolcpus=1 is in effect and working. > > Can this be an sms problem? Or is this something all aglay in the 2.8 > development branch? > > What is the best way to switch it back to the current 2.7.0 & see if that > fixes this? > > Thanks. > > 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) > 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 >
Hardware stepgen following errors usually come from the servo thread jitter If the built in position mode stepgen driver is used, its quite intolerant of servo thread jitter and goes bonkers if you have significant servo thread jitter and you dont bound its acceleration. The normal fix for this is setting the stepgens max_accel parameter to about 20% greater than the machines max_accel setting. This works acceptably in most cases but if you need better servo thread jitter tolerance, using the hardware stepgens in velocity mode and using a PID loop for position feedback (from the stepgens feedback counter) works much better In this case you set the PID parameters thusly: P = 1/servo period ( that is P= 1000 at 1 mS servo thread ) FF1 = 1.000 FF2 = number of seconds between HM2 read and write (probably about .00005 or 50 usec on a PCI system) MAX_ERROR = ~.0005 In addition to PID, in drastic cases, a config that incorporates the DPLL component can deal with latencies up to a few hundred usec. Peter Wallace Mesa Electronics ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
