>Bruce: I don't know how the system appears to be behaving, but your
>error of 20 - 30 um on the trace looks about as good as you'll get with >those scales. That's within 2-3 encoder counts of commanded position. The problems I guess I was hoping would go away is the dithering or oscillation when the machine is at rest. With a P=.1 the axis drifts, at P=1 it seems to hold steady but the PID error is terrible. P=11 the PID error is the smallest I can get, P=13 the oscillation about tears the machine apart. Adjusting anything else I can get the PID error tiny amounts better but the oscillation never seems to get better I would also like to get rid of the jerking it sometimes does when moving. It did not do this with the old controller Here are some halscope images of the dithering and jerking: https://sites.google.com/site/bmklawt/home/pid-tuning >His encoder is BOUND to have a lot of positional quantization noise, as >it is a 100 um resolution linear scale, which is equal to roughly .0004". .This is the typical DRO-grade scale I just assumed with these scales I could machine a part to within .0004, and that would be perfect, I may try some better encoders. >>>Didn't Anilam also use velocity tachs too Yes the servos use velocity >Before changing .INI values using HalScope Calibration, I recommend >modeling your system first. In other words understand where you are >closing your current, velocity, and position loops. >My PPMC system uses Yaskawa servo amps which close the current and >velocity loop, leaving EMC2 to close the position loop (only P and FF1 >are non-zero in INI). This is known as a P/PI w/FF cascade control >because its loops are >nested. Well this does seem to make some sense to me, I did tune the servos to Anilams specs following this procedure, turning pots and checking resistance at points https://sites.google.com/site/bmklawt/home/westamp-manual-tuning But the last thing it says to do is adjust the SIG pot to stop the servo from drifting, I could not get it to completely stop. There is more in depth tuning but it uses an oscilloscope and I don’t have one nor would I even know how to use it. Adjusting D doesn’t do much. Jon has said this may be as good as it gets, I'll have to cut some parts and see what it can do. Thanks all for the information. My build https://sites.google.com/site/bmklawt/home ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2dcopy1 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
