On Mon, 2007-07-09 at 14:55 -0500, Jeff Epler wrote: > On Mon, Jul 09, 2007 at 12:02:25PM -0500, Jon Elson wrote: > > Stepgen has a position-cmd input, but you really > > want to feed it a velocity. I suppose you could keep your own > > position counter, and increment or decrement it every servo > > cycle to generate steps at the desired rate. Probably you don't > > need velocity ramping for this application. > > In emc 2.1, there are "stepgen", "freqgen" and "pwmgen". > > If you want a "step & direction signal with frequency (velocity) input", > use "freqgen". If you want a pwm or "interleaved pwm" signal, choose > "pwmgen". > > In emc 2.2, the "step & direction with frequency (velocity) input" mode > is integrated into stepgen. > > For each of these components there is a manual page showing the > avaialble connections. Type "man stepgen" (etc) at the terminal prompt, or > view the manual pages online: > http://linuxcnc.org/docs/2.1/html/man/man9/stepgen.9.html (also covers > freqgen) > http://linuxcnc.org/docs/2.1/html/man/man9/pwmgen.9.html > > Jeff
The more I look at the old variable pulley system, the more complicated it gets. 110 VAC goes to a transformer primary. Secondaries are labled 3.5, 12, and 24 VAC. The 12 and 24 VAC secondary taps go to four SCR's. The 3.5 VAC goes to a diode. Each SCR input goes to a data bit out from the old controller. Each SCR and diode output are tied together and then to a 50 wV capacitor. The capacitor then goes to a fifth wire on the stepper motor. Each transistor base goes to a controller data bit out and a resistor network tied to another data bit which I assume acts as an enable. Each transistor output goes to a motor winding. So my guess is that there are four bits of supply voltage control, and five bits of motor winding control. The motor drives a vertical ballscrew which with the power off backdrives to the lowest speed position pretty well. With this in mind, I am thinking that they were tying to accommodate different motor loads for driving up, down and holding. To meet these requirements, I am thinking of using a simple open-loop stepper system where the spindle velocity would be compared to the current stepper position count, then the difference would determine the step command. This would then be filtered through PWM to four data out bits to control the effective output voltage based on step direction (36 V up, 24 or 12 V down, 12 or 3.5 V hold). At some time during system initialization the speed change system would need to be homed to one of the limit switches. Although, I just remembered that I have a spindle pulse generator for feedback. I guess there will be another PID loop to fiddle with. And, I'll have to make sure that the spindle motor and high or low clutch is on. I'm getting a little dizzy thinking about this, so I think I'll go have some lunch. Then I'll study those man pages referenced above. Hopefully, I can eat this elephant one spoonful at a time. Of course, thanks for the replies and to those who make EMC live. Kirk Wallace ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
