From: Peter C. W. <pc...@me...> - 2009-10-03 19:47:22
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On Sat, 3 Oct 2009, Eric H. Johnson wrote: > Date: Sat, 3 Oct 2009 15:18:26 -0400 > From: Eric H. Johnson <ejo...@ca...> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc...@li...> > To: "'Enhanced Machine Controller (EMC)'" <emc...@li...> > Subject: Re: [Emc-users] PWM tuning with hostmot2 and 7i33 > > Peter, > > >>> My opinion is that you should _NEVER_ use _ANY_ I until you are within a > gnats eyelash of perfect tuning. It really just gets in the way. > > I would make a test fixture so you can take a step motion, increase P until > it overshoots in response to the step, add D until theres no or very little > overshoot and repeat (increasing P and D) until you get good response to the > step input. > > Then I would make another test with a long cruise, and adjust FF1 for > minimum error. > > Only at this point would I start adding some I << > > I agree with you, and that was where I started. I then read this: > http://www.linuxcnc.org/docview/html//motion_pid_theory.html > > Near the bottom: > "If the system must remain online, one tuning method is to first set the I > and D values to zero. Increase the P until the output of the loop > oscillates. Then increase I until oscillation stops. Finally, increase D > until the loop is acceptably quick to reach its reference. A fast PID loop > tuning usually overshoots slightly to reach the setpoint more quickly; > however, some systems cannot accept overshoot." > > Regardless, the oscillation is so bad that I cannot get a starting point for > bringing in either D or I. Which is why I am suspecting I screwed up another > parameter separate from PID. I just don't see it off hand. > >>> PDM at 6 MHz is correct, but is it selected (PWM is default)<< > > I am using both the 7i43 and 7i33, so the use of pwm or pdm is entirely > internal to the Mesa products. The amplifier only cares about the resultant > analog output. Which works best with the 7I33, pwm mode or pdm mode? What > are the optimal settings? PDM 6MHz, PWM/PDM selection is a HostMot2 setup option > > Thanks, > Eric > > > > ------------------------------------------------------------------------------ > 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...@li... > 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. |