Bas Laarhoven wrote: > Ah, thanks John, you made it very clear! So in my situation the input > sampling moment is fixed (at the start of the thread) and only the > update of the output varies with the variations in processing time. You > state this will probably have no noticeable effect, but as this > variation is a significant part of the PID cycle time, wouldn't it be > better to reduce the variation (noise) and work with a fixed although > increased delay? Another option is to lower the loop update frequency as > that reduces the noise in more than one way. Do you know of a rule of > thumb for the cycle time in relation to the system response time ? >
The tradeoffs of increasing the period in order to reduce the uncertainty (jitter) are getting rather deep into control theory. I don't know myself which would be better - it is probably very dependent on both the system characteristics and your goals. I would not worry about it unless and until you actually see a problem. They try testing various approaches to see what solves the problem. I really think you may be worrying too much - try it and see. Regards, John Kasunich ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
