Dave wrote: > Backlash is a difficult thing to handle and it just gets worse when you > try and put a PID loop around it. > > Backlash is like having a loose shaft coupling with slop in it. > > Pretty much a control nightmare. > Yes, a simple control algorithm requires a linear function between command and output. Backlash is perfectly non-linear, therefore it makes the whole control loop go "wild" until the screw is at the other end of the backlash. A small amount of backlash is tolerable, and a number of tweaks to the classic PID, such as deadband, allow the loop to function. But, when you get to the point that the deadband is large enough to interfere with the desired accuracy of positioning, then you can't tolerate it.
Jon ------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
