Don Stanley wrote: > > When the OUTPUT_SCALE is set to +1.0 I was getting 1 step output for > each inch of travel. That was actually .000004 inches of movement for > 1 inch movement shown on the axis display. My drives need 125000 steps > per inch of travel (250000 steps on the knee). When I set the OUTPUT_SCALE > to 125000 move starts became very rough and stalled the motors. I had to > change the MAX_ACCELERATION = from 20 to 1 (or less) to get a top speed of > 40 inches per minute (as opposed to 60 ipm in non servo mode). > > Does all this compute with you? > UGH! It is embarrassing when I discover I know so little about the products I designed! Well, all I can use to excuse myself is that only a few users actually use the closed-loop stepper mode. So, I don't delve into it often enough to remember how it works. I sort of think I mentioned before that INPUT_SCALE should equal the encoder resolution, and OUTPUT_SCALE should equal the steps per unit resolution, but then I think I contradicted myself. Maybe I need to put definitive comments into the sample files so people know what to do.
OK, now you probably have the scale factors right, and you will have to tune the servo response. You need to start up halscope from the machine menu, and then the calibration menu from the same main menu, and adjust the P, D and FF1 and FF2 settings for best response. Watch ppmc.0.encoder.00.delta (gives encoder velocity in raw count units per servo period) and set the scope to trigger off that channel. Then also add a trace for pid.0.error These two traces allow you to see how well it accelerates and follows the desired moves. See http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?PWM_Servo_Amplifiers for some help and sample pictures from this process. The above page was written for my PWM servo system, so some of the response may be just a little different, but the general process and the interpretation of the graphs should be quite similar. Jon ------------------------------------------------------------------------------ Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! Tap into the largest installed PC base & get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
