Chris Radek <[EMAIL PROTECTED]> wrote: > On Mon, Oct 08, 2007 at 11:33:12PM -0600, Sebastian Kuzminsky wrote: > > What kind of leadscrews are you using? > > they are the 1mm pitch triangular thread that came on the machine. > > This gives a scale of 6000 counts/mm, too high for software counting > at much speed. With the Pluto I run it at 1500mm/min (about 60 ipm)
How do you keep your motor speed down to levels the encoder-reader can keep up with? IIRC, the pluto-servo firmware samples the encoder lines at 40 MHz, which should be fine for any reasonable machine-tool cnc servo motor, so this is probably no longer something you worry about. With software encoder-reading over the parallel port, 40 or 50 KHz sampling frequencies seem reasonable. With a 500-line encoder this gives a max motor-shaft speed of ~600 rpm, which seems quite low. It's 30 ipm if you have a 1:1 transmission to a 20 tpi leadscrew. Worse if you're gearing up your torque. Better if you have steeper threads on your leadscrew. I've been thinking of trying to implement a two-PID servo control loop with EMC. The first loop would be the normal position controller, with pid.feedback from encoder.position and pid.command going to a second PID loop. The second PID loop would try to do speed control; it would get its feedback from encoder.velocity and send its command to pwmgen.value. Has anyone tried anything like this? Or maybe I should just buy one of Peter's 5i20 boards. ;-) -- Sebastian Kuzminsky ------------------------------------------------------------------------- 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
