On Fri, 2008-06-06 at 11:11 -0500, Jon Elson wrote: > Kirk Wallace wrote: > > On Thu, 2008-06-05 at 21:19 -0500, Jon Elson wrote: > > ...snip > > > >>If you have a spindle encoder, you could make HAL read the encoder > >>velocity and add a correction to the PWM output. > >> > >>Jon > > > > > > It was talked about before, but I don't remember the outcome. The > > software encoder has a velocity output pin, but ppmc and other hardware > > drivers don't? > > > The PPMC driver does have "delta", which is velocity in encoder > count units. For a spindle, I guess it would be scaled from 0.0 > to 1.0, but my driver doesn't do this. It could be added fairly > easily. There might be glitches in delta when the spindle syncs > to the index pulse. Clamping the value of delta to some > reasonable maximum for the RPM and pulse count would be a good > thing to do. I'll have to do some experiments with this, I am > going to be setting up a spindle speed control to demo at the > CNC Workshop. > > Jon
Thinking aloud, there might be three elements; motion.spindle, pid.X and ppmc.X.encoder/pwm. Connecting the enable signal should be fairly simple: net SpinEN motion.spindle-on => pid.X.enable ppmc.X.pwm.X.enable Connecting the speed command (RPM): net SpinSpCmd motion.spindle-speed-out => pid.X.command Then pid.X.out would be scaled/converted to a number between 0 and 1 corresponding to the percentage of commanded spindle speed and fed to pwm.X.value?. This would be inversely proportional to the feedback encoder counts per base/servo period. I seem to recall encoder count wrapping and/or resetting is an unresolved issue. Feedback would start with ppmc.X.encoder.X.delta? Is encoder delta reset to zero and at what event? This would then be scaled/converted to RPM and fed to pid.X.feedback and possibly a speed display. It looks like there is still some magic that needs to conjured before this will work. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
