Hi Andy, The system currently uses PWM to a cheap (not the most linear) 0V-10V converter. Which means the PWM values for requested RPM at 100 should different than the requested PWM for RPM at 1500. All because originally the BIT file I was using for the 7i92H did not have an extra step/dir on the first parallel port and I still required the system to run off a single port for either LCNC or MACH3. With MACH3 it's easy. Change a check box for step/dir or PWM and it uses the same port pins. Hence the system is still wired for PWM.
Also the spindle pulley ratio is about 1.040/1.000 if the requested verses target speeds are to be believed. Before I added the quadrature feedback I was using a limit block I called spindle-ramped. That's because the Bergerda AC servo drive is extremely well tuned and the motor does what it's asked to do almost instantly. So a change from say 700 to 200 RPM felt jerky. Hence adding the ramp to move up and down in speed more slowly. I removed that ramp block once the encoder was there. I've put the ramp block back in but set .maxv back up to the largest value. Set .max to largest value and set .min to 0. Now when told to go to 0 RPS it goes to 0 and not in the reverse direction which the spindle would rapidly do if given a negative value that changed the direction output. A PID outside another PID is never really a good idea. In either case, I've set FF0 down to 0.68 and bumped up the P and I which makes the system more responsive and reached the target velocity faster which means the up to speed indication is there sooner and tapping begins sooner. It was the retraction of the tap that had me worried as the change in direction and lagging spindle speed made it look like it would break taps. Although if I understand the G31.1 correctly the Z axis tracks the encoder reported speed right? So the spindle speed before the tapping starts and for reversing is really more of a guide than an actual written in stone value? In other words, is the PID even needed? John > -----Original Message----- > From: andy pugh [mailto:bodge...@gmail.com] > Sent: July-09-21 12:44 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Runaway PID spindle. > > On Fri, 9 Jul 2021 at 01:20, John Dammeyer <jo...@autoartisans.com> wrote: > > > If I set it to 0.05 then the spindle does stop but now the PID isn't very > > responsive. I have to add large amounts of P and I to get it to > stabilize quickly and at 100RPM it then surges > > I would expect a spindle PID to mainly rely on FF0 and I. > (Set the FF0 to give the right speed at a mid-range point without any > P, I or D) > > You could _try_ running the PID output through a limit block, so that > a negative value can't get through, but the PID will still output a > negative value, and might get "confused" if that has no effect. > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > � George Fitch, Atlanta Constitution Newspaper, 1912 > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
