John, Ok, got it. Fractional values for PID values just didn't seem right, but after closer inspection I see how it would work out that way. It wasn't that close to a divide by 360 however, more like divide by 60, at least for P. I and D were already too small to establish a meaningful proportionality.
I had not really thought through the consequences of giving scaled, real world positions to the pid component's command and feedback pins, as opposed to raw encoder positions, as is the case with most other types of motion systems I have used. ISTM there are advantages to using raw encoder values rather than real world positions for PID tuning, in that it eliminates the effects of a number of variables such as gear ratio and acceleration (real world, as opposed to encoder counts per sec^2). It also means that the same motor / encoder pair should have the same, or very close to the same pid values, regardless of gearing or other scaling (linear vs. angular for example). Regards, Eric Write down the PID gains that work when the scale is 18400. Then, since you are dividing the scale by 360 to get 51.1, you should be able to also divide the gains by 360, and the resulting PID results should be identical. Take the old gains, divide by 360, and try them as a starting point for tuning. ------------------------------------------------------------------------------ Come build with us! The BlackBerry® Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9-12, 2009. Register now! http://p.sf.net/sfu/devconf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
