2009/6/25 <a...@conceptmachinery.com>: > Sequences 1-3 very clear. > Sequence 4 – means increase D until graph will be represent with line and > not with line that has noise (vibration type). > Am I right here? > Sequence 5. What is mean instability? Is this same as an oscillation?
Yes, exactly, > I know what oscillation means, but what instability is and how it will be > represented on Hal Scope. In this context they are much the same thing, though perhaps different in detail. An oscillation is probably meant to describe a periodic and increasing failure to meet a step change in the setpoint, and an instability might be random variations in a position when there is no change in setpoint. You seem to be describing Ziegler- Nichols tuning, and a google search on those words should help with more detail. http://en.wikipedia.org/wiki/Ziegler–Nichols_method as a starting point However, Z-N tuning is most effective for symmetric systems, you might still get better performance with hand tuning from those base points. My personal experience is "Beware of D" especially in any system with backlash. [Irrelevant detail] in my real job we run controllers where P I and D are themselves functions of other things, including noise factors such as fuel temperarature and simple factors such as distance from setpoint. PI and D are not the be-all and end-all of control, and if that is all you have then perfection (and indeed adequacy) might be unobtainable) -- atp ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
