On 6/5/2011 1:50 PM, dave wrote: > On Sun, 2011-06-05 at 13:13 -0400, Dave wrote: > >> On 6/5/2011 10:58 AM, dave wrote: >> >>> Hi all, >>> IRC seems pretty dead this morning so I'll try here. >>> >>> I seem to remember cradek doing a velocity to dac signal to emulate a >>> tach. However I cannot seem to find documentation. >>> Board is a 5I20 running hm2 so the velocity signal should be there. >>> I just need the hal commands to get started. >>> >>> I've been using a Keling 750 W servo motor with a 2:1 and a 10 mm pitch >>> ballscrew to drive the Z on my Cinci contourmaster. In torque mode I >>> have stability problems; I finally ended up getting the following error >>> down to about .002 ... pretty bad .. and that is after about 8 hours of >>> tuning! This is usable for some things but doesn't do well for >>> contours. >>> >>> Plan 1. go to velocity mode and add a tach. The tach is low output. >>> only about 2.5 V/1000 rpm. For some reason I can't get the system >>> stable. When enabled it oscillates for a few seconds and faults. >>> That is with the analog input at zero (shorted). >>> I've moved the tach gain all over the place with no luck so far. >>> >>> >>> Plan 2. add the synthetic tach as per cradek. >>> >>> Plan 3. install a SEM servo motor with a known tach output. >>> The X axis of this machine already has an SEM so I know it will >>> work. :-) >>> >>> I'm open to ideas and opinions. >>> >>> Dave >>> >>> >> Forgetting about EMC2 for a moment; >> >> With the drive in velocity mode, if you short the analog to input the >> Servo drive you should be able to adjust the zero offset and gain so the >> motor is somewhere between dead still to creeping. No oscillating. >> > Exactly! > > So back to the drawing board. ;-) > >> If you can't do that you have a drive/motor/encoder and that will not be >> resolvable with EMC2 tuning. >> >> How many encoder counts do you have per rev? >> > 2500 cpr or 10K in quadrature. > > At Peter's suggestion I checked the servo cycle. > servo cycle was set at 250000. I think I tried faster setting when I was > originally tuning but got errors. > > dave > >
2500 cpr is plenty .. the drive and motor should be very stable without EMC2 connected. EMC2 won't be able to control that properly until the drive/motor itself is stable, otherwise the motor will go off and do its own thing (oscillate out of position) and EMC2 will fault out due to following errors. >>So back to the drawing board. ;-) Unfortunately... Dave ------------------------------------------------------------------------------ Simplify data backup and recovery for your virtual environment with vRanger. Installation's a snap, and flexible recovery options mean your data is safe, secure and there when you need it. Discover what all the cheering's about. Get your free trial download today. http://p.sf.net/sfu/quest-dev2dev2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
