Sebastian Kuzminsky wrote: >Jim Combs wrote: > > >>You might not be the right person to answer this, but is it possible to >>create a Auto-Calibrate >>mode where the system would run an axis in a series of short moves in both >>directions where >>the move time is monitored and the motion variables adjusted automatically >>to try and get >>the most optimum settings. Have a list of variables to adjust and a flag >>for the user to indicate >>auto adjust. Are there some initial values that would most if not all the >>time, and let the system >>optimize the settings. >> >> > >I think it'd be easy to automate a PID tuning system like >Ziegler-Nichols ><http://en.wikipedia.org/wiki/PID_tuning#Ziegler.E2.80.93Nichols_method>. > >It'll get you in the ballpark at least. > > EMC2 has a component called "at_pid", which is an autotuning PID. It uses something like Z-N to get the coefficients. In testing, it seemed to create usable sets of coefficients, but the results were pretty heavily dependent on initial conditions. You could tune an axis twice, and you'd get two very different sets of coefficients. Both seemed like they would work OK, but the fact that the results were so dependent on initial conditions led most everyone, including the author of the component, to question whether it was a good idea to use it.
I don't know if auto-tuners can tune feedforward - I've never heard of one that does (though I haven't looked hard). Feedforward lets the PID feed control commands straight through (mroe or less), and then adds on the error correction terms. There's just no substitute for having a brain in the process somewhere - computers can't do it all (yet). - Steve ------------------------------------------------------------------------------ Check out the new SourceForge.net Marketplace. It is the best place to buy or sell services for just about anything Open Source. http://p.sf.net/sfu/Xq1LFB _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
