On Sun, 5 Jun 2011, dave wrote: > Date: Sun, 05 Jun 2011 07:58:52 -0700 > From: dave <[email protected]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: "Enhanced Machine Controller (EMC)" <[email protected]> > Subject: [Emc-users] synthetic tach > > 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 >
Torque mode often requires higher loop bandwidth (as EMCs PID loop now controls the higher bandwidth velocity portion of the control loop). Have you tried speeding up your servo thread (to 2 or 4 KHz perhaps). A 1 KHz servo loop rate with first order hold has about a 300 Hz bandwidth. This may not be high enough to get the desired loop gain with enough phase margin to make it stable. Also, I assume you aren't tuning a bare motor, this is nearly impossible in torque mode... > > > > ------------------------------------------------------------------------------ > 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 > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ 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
