Re: [Emc-users] odd PID tuning problem

2010-07-09 Thread Jon Elson
Andy Pugh wrote: > On 9 July 2010 17:47, Jon Elson wrote: > > >> Why is the P term so low? >> > > Perhaps his error is in mm? > Yes, sure, that would scale it down by 25.4, but 3 still seems to be VERY low. Jon -

Re: [Emc-users] odd PID tuning problem

2010-07-09 Thread dave
On Fri, 2010-07-09 at 11:47 -0500, Jon Elson wrote: > Jake Anderson wrote: > > > > Currently I am running a > > P of ~3 > > D of .01 > > FF1 0 > > FF2 .03 > > FF2 .0001 > > > Why is the P term so low? Can you raise it? I know the Mesa is > different from my boards, > but I use P values from 5

Re: [Emc-users] odd PID tuning problem

2010-07-09 Thread Andy Pugh
On 9 July 2010 17:47, Jon Elson wrote: > Why is the P term so low? Perhaps his error is in mm? -- atp -- This SF.net email is sponsored by Sprint What will you do first with EVO, the first 4G phone? Visit sprint.com/f

Re: [Emc-users] odd PID tuning problem

2010-07-09 Thread Jon Elson
Jake Anderson wrote: > > Currently I am running a > P of ~3 > D of .01 > FF1 0 > FF2 .03 > FF2 .0001 > Why is the P term so low? Can you raise it? I know the Mesa is different from my boards, but I use P values from 50 to 4000 or so. I think this is the real reason you have different error

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Jake Anderson
On 08/07/10 13:01, dave wrote: > On Wed, 2010-07-07 at 20:43 -0500, Chris Radek wrote: > >> On Thu, Jul 08, 2010 at 10:32:50AM +1000, Jake Anderson wrote: >> >>> We have converted our mill to CNC and EMC2 and all is fairly well. >>> http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?JakeAndRusse

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Jake Anderson
On 08/07/10 11:43, Chris Radek wrote: > On Thu, Jul 08, 2010 at 10:32:50AM +1000, Jake Anderson wrote: > >> We have converted our mill to CNC and EMC2 and all is fairly well. >> http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?JakeAndRussells >> > ... > > >> Unfortunatly when I change that

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Jon Elson
Stephen Wille Padnos wrote: > Jon Elson wrote: > >> This is pid2, but it still doesn't solve the quantization noise in the >> encoder-derived velocity. >> >> > Actually, it does. The Mesa encoder counter has a timestamp of when the > last encoder edge was seen, so the velocity is base

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Stephen Wille Padnos
Jon Elson wrote: > [snip] >> Dont know if EMCs PID loop has been modified to allow an external (not >> DPosition/DT) velocity input. If the PID component had a velocity input, you >> could use HostMot2s encoder velocity output as a better velocity feedback >> term >> than the (crunchy) DPosition/D

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Jon Elson
Peter C. Wallace wrote: > > Does you motor power supply droop when doing a fast move? With a bare Hbridge > (Voltage mode), FF1 is needed to compensate for the motors back EMF, I believe FF1 compensates mostly for motor resistance, not back EMF. Back EMF turns the servo motor into a velocity ser

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Jon Elson
Andy Pugh wrote: > I _think_ what you would have in such a dual PID loop would be a loop > closed by velocity but controlled by duty-cycle (and motor torque is > at least approximately directly proportional to PWM duty cycle) driven > by a loop closed by position and controlled by velocity. > >

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Jon Elson
Chris Radek wrote: > > I see you're using bare H bridges which means you don't have a > velocity loop. I think this problem with FF1 is because of that, and > it is a fairly fundamental problem with a torque-mode setup. > > My PWM servo system is very similar, essentially a voltage-mode amplifi

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Peter C. Wallace
On Thu, 8 Jul 2010, Jake Anderson wrote: > Date: Thu, 08 Jul 2010 10:32:50 +1000 > From: Jake Anderson > Reply-To: "Enhanced Machine Controller (EMC)" > > To: "Enhanced Machine Controller (EMC)" > Subject: [Emc-users] odd PID tuning problem > > We have converted our mill to CNC and EMC2 an

Re: [Emc-users] odd PID tuning problem

2010-07-08 Thread Andy Pugh
On 8 July 2010 02:43, Chris Radek wrote: > One step more complicated is to have dual pid loops, a torque loop > inside a velocity.  I'm not sure what you'd use for torque/current > feedback, though.  Normally that's current sensing in hardware, and > you have no equivalent that I can see. I _thi

Re: [Emc-users] odd PID tuning problem

2010-07-07 Thread dave
On Wed, 2010-07-07 at 20:43 -0500, Chris Radek wrote: > On Thu, Jul 08, 2010 at 10:32:50AM +1000, Jake Anderson wrote: > > We have converted our mill to CNC and EMC2 and all is fairly well. > > http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?JakeAndRussells > > ... > > > Unfortunatly when I change th

Re: [Emc-users] odd PID tuning problem

2010-07-07 Thread Chris Radek
On Thu, Jul 08, 2010 at 10:32:50AM +1000, Jake Anderson wrote: > We have converted our mill to CNC and EMC2 and all is fairly well. > http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?JakeAndRussells ... > Unfortunatly when I change that cruise speed (g1 F200 vs G1 F100 say) > the ferror goes up, and