On Thu, 2007-10-11 at 20:53 -0500, Jon Elson wrote: > Kirk Wallace wrote: > > What is the status of PID_MAX_VEL and PWM_OUTPUT_SCALE? My understanding > > is that they were created to fix persistence issues. I am using EMC > > 2.1.7 so should I still use them? > > > Arrghhh! I don't actually know. PID_MAX_VEL is a standard part > of the modern ini file, and should still be used. It is to > allow the servo algorithm to have a little extra headroom for > acceleration.
So PID_MAX_VEL is not unique to the UPC? > PWM_OUTPUT_SCALE is an anachronism, as you say above. The best > way to find out if it is still active is to do the following, > after doing a cd to the configs directory you are using: > > grep PWM_OUTPUT_SCALE *.hal > > This will scan all the hal files for use of this parameter. If > it doesn't show up at all, then it is not being used. > > Ahh, I have done it for you : > # set output scaling from ini file > # note that these are using PWM_OUTPUT_SCALE - they should > # use OUTPUT_SCALE, but right now EMC2 re-writes that to > # 1 on shutdown for some reason. Once that is fixed, this > # should be changed > setp ppmc.0.pwm.00.scale [AXIS_0]PWM_OUTPUT_SCALE > setp ppmc.0.pwm.01.scale [AXIS_1]PWM_OUTPUT_SCALE > setp ppmc.0.pwm.02.scale [AXIS_2]PWM_OUTPUT_SCALE > > You can just change these lines in hnc_motion-3a.hal > > and remove the PWM_ from the 3 lines above. Then, remove the > now redundant lines with PWM_OUTPUT_SCALE from your ini file. For some reason that I can't recall, the above did not work for me right away, so I put PWM_OUTPUT_SCALE back the way it was, set it to -1, zeroed out the pid/ff settings and started over. Now I have P set to ~50 and FF1 set to .25 and everything else set to 0. My FERROR is now .0050 and MIN_FERROR is .0013. Typically, I am getting .0005" difference between the commanded position and the actual position, which is better than a couple of days ago, but I am hoping to do better. I just need to put in more effort. > But, then, I think you will find that if you turn OUTPUT_SCALE > back down to -1, you will get MORE voltage out of the servo amp. > OUTPUT_SCALE (which is just an ini parameter for the hal > parameter ppmc.0.pwm.xx.scale is a DIVIDER, not a multiplier ... snip > > There's really no reason to mess with output scale, other than > making the sign correct to close the loop, as P does the same > thing (although it IS a multiplier). > > Jon -- Kirk Wallace (Hardinge HNC lathe, California, USA http://www.wallacecompany.com/machine_shop/ ) ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
