On Tue, 22 May 2012 13:43:33 +0000 erik.555.gr...@gmail.com wrote: > Are there any major dis-advantages to using glass scales as position > feedback for a servo system versus using encoders directly attached > to the motors. I could see where backlash might be an issue but if > using precision ground ballscrews........
Used alone I think there is a disadvantage. The low count simply adds to the quantization problem i.e. not enough counts/servo cycle. The hybrid approach I think is almost ideal. I'm beginning to think that using a gear train between the servo motor and the encoder may have advantages especially where one uses a glass scale for final position. I recently took and encoder off the end of the servo motor where I had iffy mechanical implementation and used a small timing gear to put the encoder on the coupling belt between the servo motor and the ballscrew. After I got the timing gear done correctly; it had come loose and was driving me even more nuts. ;-) ( I helped it with a bit of blue locktite. :-) I now have just over 100K counts/inch which makes tuning really nice. The axis also has a glass scale but I've not hooked it to I, yet! The glass scale is a 10 um so a bit coarse but just fine for my well used machine. There is a difference between control and accuracy and few well used machines will hold better than a thou. Sorry for rambling on. HTH Dave BTW- there is agreement between the encoder (emc display) and the glass scale on a accurite dro of at worst one or two counts. > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. > Discussions will include endpoint security, mobile security and the > latest in malware threats. > http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
