On Thu, Feb 3, 2011 at 7:16 AM, Slavko Kocjancic <esla...@gmail.com> wrote:
> That's not problem of friction at all!. > > The worst you have is 'sticky' axis. > That means you need a lot more power to start to move axis and when already > moving the required power is a way smaller. > No. This is an axis with friction. The opposing force dows not diminish with movement. > And if that ratio is big then tuning PID is near imposible. You can have > low > static error or low (or none) overshots but not the both!. > So in this point of view the mechanics is bad nad electronic's can't do the > job. > The ratio can be measured with spring scalle. > Just make arm on screw and then pull that arm with scale. Slowly pull until > axis move then stop pulling and you have reading just at the point before > start and when stoped. (you need some support for pulling as if you pull > with bare hand then the 'stop' can't be measured as hand is to 'springy') > And if ratio is biger than 1:2 then you have serrious problem. > > It is definitely regular friction. i > > > 2011/1/26 Igor Chudov <ichu...@gmail.com> > > > I have a rotary table (4th axis) that has considerable friction. > > > > I know this because the DC servo motor requires at least about 4 amps, to > > turn the table. > > > > The rotary table has a tight worm drive, not some sort of a ballscrew, > and > > the drive is hard to turn. I did try that without the motor, by hand, and > > it > > was clearly a bit hard to move. > > > > I finally got the table work with EMC2 (thanks to Jon), and have a > problem > > with is a high following error. The error is 0.04 degrees. Since there is > a > > considerable reduction ratio in the work drive, the following error > amounts > > to something like 5 degrees of a turn of the motor (I may be off with my > > math VERY easily, but clearly it is huge with that much reduction). > > > > Right or wrong, I attribute this to the friction in the worm drive system > > -- > > the servo motor develops following error when working against friction. > > > > I have AMC DC drives working in torque mode. > > > > My question is what servo tuning parameters could I use to compensate for > > high friction. It seems that I almost need FF(-1) or something like that? > > > > Thanks > > > > i > > > > > ------------------------------------------------------------------------------ > > Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! > > Finally, a world-class log management solution at an even better > > price-free! > > Download using promo code Free_Logger_4_Dev2Dev. Offer expires > > February 28th, so secure your free ArcSight Logger TODAY! > > http://p.sf.net/sfu/arcsight-sfd2d > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > ------------------------------------------------------------------------------ > Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! > Finally, a world-class log management solution at an even better > price-free! > Download using promo code Free_Logger_4_Dev2Dev. Offer expires > February 28th, so secure your free ArcSight Logger TODAY! > http://p.sf.net/sfu/arcsight-sfd2d > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! Finally, a world-class log management solution at an even better price-free! Download using promo code Free_Logger_4_Dev2Dev. Offer expires February 28th, so secure your free ArcSight Logger TODAY! http://p.sf.net/sfu/arcsight-sfd2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
