On 5/8/2012 4:22 PM, andy pugh wrote: > On 8 May 2012 21:06, Dave<[email protected]> wrote: > > >> You have no Pgain, but Igain and Dgain. That's a problem. An all I and >> D loop is almost always unstable. >> > That depends…. > > For a spindle P gain is not much help, as you need a non-zero PID > output even when at the set speed (and when the error is zero). That > is why the Wiki example is all-I. I assume that FF0 wasn't available > when that page was written. > > I spent most of this afternoon at work tuning something that turned > out to work best with 99% of the control coming from the D-term and 1% > from I. But that was a rather unusual situation. > >
Andy .....That is really unusual! >>For a spindle P gain is not much help, as you need a non-zero PID output even when at the set speed (and when the error is zero).<< I agree.. but the output will move if some error exists.. if you only have a P term, but the error will never be zero of course. (just trying to start conservatively so the output doesn't bang into the limits - this stuff is hard to describe) Then dialing in a small amount of I term should move the bias portion of the output (the "I" contribution) and things should start to work. Dave ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
