On Tue, 22 May 2012 18:39:05 +0200 Roland Jollivet <roland.jolli...@gmail.com> wrote:
> On 22 May 2012 15:51, John Kasunich <jmkasun...@fastmail.fm> wrote: > > > It can be (and has been) done. You probably will need to keep the > > encoders on the motors, unless your ballscrews and the rest of the > > drivetrain is very tight and backlash free. The trick is to use the > > motor encoders for the P and D parts of the PID loop, for stability, > > and use the linear scales for the I part, to correct the small > > and fairly slow-changing error between the screw and the scale. > > > > Follow the link below for a blog posting about how we did exactly > > that on a large boring mill: > > http://jmkasunich.com/cgi-bin/blosxom/shoptask/wichita-trip-02-20-08.html > > > > > > On Tue, May 22, 2012, at 01:43 PM, 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........ > > > > Does this mean you can use lower resolution encoders on the motor, or > should they be similar? > If you had 1um resolution on the fixed linear scale, what linear > resolution should the rotary encoder yield? > > Regards > Roland IMHO ... as high as you can realize without overflowing the bandwidth of the encoder channel. If you can pickup encoders off dead red_cap Fanuc motors you should do very well. I think Jon Elson has doped out how to decode them. :-) Again anything you can do to reduce the digital jitter (quantization) at low to the high end of practical speeds will improve your motion. Dave > ------------------------------------------------------------------------------ > 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
