On 05/29/2015 08:23 PM, Mark Johnsen wrote: > I have made huge strides on my Supermax conversion from an Anilam Crusador > M to a 5i25/7i77. I was very happy to have the encoder resolution and > motor/encoder directions setup so that I can start tuning. I was able to > follow John Thornton's Velocity tuning instructions, but I have the > almighty dither... > > Specs for the system are West Amp Servo's w/ tach feedback and 0.01mm > resolution glass scales connected to the 7i77. > > Has anyone been able to tune this system and remove the dither without an > additional high-res encoder added to the system? > > One thing nobody has mentioned is you will never get the dither to be less than the backlash between motor and linear scale. There are several components to this. Coupling or belt between motor and screw, end bearing on screw, ballnut, mount for ballnut, and possibly bow of the ballscrew. Also, any rocking of the slide ways that causes the ways to skew differently when pushed in the plus and minus direction will have a similar effect. If the total of all these backlash components is over .002" you will just go nuts trying to resolve it, and no amount of software will ever make it go away. If you can get the total backlash down to .0005" or so, then you should be able to accomplish a good tune of the PID that will settle without buzzing or other dither effects.
Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
