On Thu, 5 Jul 2012, Ralph Stirling wrote: > Date: Thu, 5 Jul 2012 17:39:41 +0000 > From: Ralph Stirling <[email protected]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: "Enhanced Machine Controller (EMC)" <[email protected]> > Subject: Re: [Emc-users] linear motor tuning questions > > That did it! D=0.12 gives me much smoother f-error at > higher accelerations. I had always assumed that derivative > term would make oscillations worse, so didn't play with it > much. At D=0.14 new oscillations appear, but at D=0.08 to > 0.12 the 10Hz resonance disappears. > > Thanks again! > -- Ralph
With a simple voltage or current mode drive D is absolutely needed for decent performance (and for velocity mode drives its still there but handled the drive). One way of looking at this is with only P term and a torque mode drive you have a spring (the P term) and a weight (the system mass) which make a nice bouncy oscillator. You need to add damping to this to make it stable (damping is a force in proportion to and in the opposite direction to the velocity) this is what the D term does. If you want a 'gut' feeling for what these terms do and you have a small enough system that you can safely push it around by hand, Try setting P=0, D=.12, I=0 and pushing your carriage around Then try small bits of the other (P an I) terms by themselves (note I by itself and no P will eventually oscillate quite wildly) Peter Wallace Mesa Electronics ------------------------------------------------------------------------------ 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
