On 1/27/2012 9:18 PM, Jon Elson wrote: > Peter C. Wallace wrote: >> >> This is wrong, you add D to make it more stable not I >> > This thing about add I to increase stability is in several places in the > docs and Wiki,
Jon: I don't remember reading this when I was reviewing the V2.5 docs. As a counterexample, looking at the HTML files under http://www.linuxcnc.org/docs, in section 1.2.4 "Derivative Term" of "Important Integrator Concepts" in the V2.4 docs (which becomes section 2.4 of "Integrator Concepts" in V2.5 docs), it says "The derivative term slows the rate of change of the controller output and this effect is most noticeable close to the controller set point. Hence, derivative control is used to reduce the magnitude of the overshoot produced by the integral component and improve the combined controller-process stability." In section 1.1.3 "[Loop Tuning] Simple method" of "PID Theory" in V2.4 (mutatis mutandi for V2.5) it says "If the system must remain on line, one tuning method is to first set the I and D values to zero. Increase the P until the output of the loop oscillates. Then increase I until oscillation stops. Finally, increase D until the loop is acceptably quick to reach its reference." I don't interpret this simple method to mean "add I to increase stability" but perhaps that just shows I don't know PID theory and practice. > and I was wondering about this. I agree with you that it is D that > increases stability > (up to a point). If this is truly a typo, we need to get it corrected. If you could identify the problem sections I'd be happy to help reconcile them. > Jon > Regards, Kent ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
