On Tue, 7 Apr 2009, Tom wrote: > Date: Tue, 7 Apr 2009 18:21:03 +0000 (UTC) > From: Tom <kestrel...@yahoo.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] ilowpass filter > > Jon Elson <el...@...> writes: > > >>> >> What servo drives are you using? > > I am using Advanced Motion pwm brush type amplifiers. > See here: http://www.a-m-c.com/download/datasheet/30a20ac.pdf > > snip... >> >> This problem has been bugging me for some time, and I am planning to >> work on it at the EMC Fest in May in Wichita. My general plan would be >> to put in a fairly simple digital notch filter at 1/2 the sample rate. >> Maybe somebody well versed in control theory can expound on the >> implications of this, and whether it would be better to have a sharp >> notch or a more gradual rolloff starting a little below 1/2 f. >> >> Buzzing at rest may be eliminated by adding a little deadband. >> Depending on encoder resolution, a deadband equal to a couple encoder >> counts will often stop the oscillations entirely, or make them sporadic. >> >> Jon > > > Wow... thanks Jon. I may have to re-read this several times until it sinks in. > I will try setting the servo-thread rate higher and see how it reacts. > > Increasing deadband works from experience, but I will have to do some test > cuts > and see if following error is tolerable. > > Tom > >
Also (connecting some dots here) if you are using HostMot2, D term crunchyness should be much improved when EMCs PID loop is modified to be able to use the drivers Velocity output (which uses DeltaCounts/DeltaTime velocity estimation). This should allow larger D terms without instabilities > > > > > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by: > High Quality Requirements in a Collaborative Environment. > Download a free trial of Rational Requirements Composer Now! > http://p.sf.net/sfu/www-ibm-com > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
