Referring to: http://imagebin.org/72841 I've added the motor-pos-cmd trace.
Jeff Epler wrote: > The coarse-position-command is the motor position before applying screw > compensation or backlash compensation, so it differs from the > motor-pos-cmd on machines that have these compensations enabled. > I don't use screw or backlash compensation so I guess coarse-pos-cmd should equal motor-pos-cmd. 'A' shows two servo periods. Am I correct in thinking that the compensation is added to coarse-pos-cmd on the first period value and hal displays it on the second period? > Additionally, the ferror is computed from the *prior* commanded position > and the *current* motor position, but halscope captures after commanded > position is updated. On the other hand, PID error is the difference > from the *current* motor position and *current* commanded position; this > is why PID error and ferror are not equal either. > So in other words, the f-error at 'B' is equal the difference at 'C'? However, if the motor-pos-cmd at 'C' is derived from coarse-pos-cmd two periods earlier, it seems to me that the f-error at 'B' is really around half of that displayed - I must be wrong, I would be delighted if you would put me right :-) Thanks, Richard ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
