Hello Andrew, I'm finishing some parts of the enclosure for the PC on the retrofitting we're doing to our lathe. I'm planning to do the same thing you want to do. Using step mode and being able to home with index. I recall reading on the forum a post from Andy telling that it's more than possible to achieve that. So it's a matter of trying it out.
I'm almost done with the preparation for the retrofit but the final step which is installing all the new hardware and polishing the details will be taking place in march. Anyway, in a few days I'll be testing the servos in step mode outside the machine so I'm planning to simulate homing with index by then. I hope this works because I prefer the simpler mechanical setup of the servos in open loop. I'll tell you by then if I succeeded testing it out. El 10 feb. 2020 21:14, "andrew beck" <[email protected]> escribió: Awesome Todd What Mesa card did you use? And do you mind if I pick your brains on this rather than reinventing the wheel. I would love to see a config that works so I can compare it with what I have and make the needed changes. Also did you find the motion was uneven or did it just work as expected. Regards Andrew On Tue, Feb 11, 2020, 11:20 AM Todd Zuercher <[email protected]> wrote: > It works very much similar to running them with an analog input. The > encoder feedback can also be handy for double checking the tuning of your > servo drives. > > You simply disconnect the position feedback from the stepgen and use the > feedback from the encoders to connect to the PID and the joint position-fb. > > You will need to tune the feedback loop, P=1000 will no longer be valid, > and will likely have to be significantly less (guess 1/2-2/3) > > Todd Zuercher > P. Graham Dunn Inc. > 630 Henry Street > Dalton, Ohio 44618 > Phone: (330)828-2105ext. 2031 > > -----Original Message----- > From: andrew beck <[email protected]> > Sent: Monday, February 10, 2020 4:46 PM > To: Enhanced Machine Controller (EMC) <[email protected]> > Subject: Re: [Emc-users] closing the loop in linuxcnc with a 7i76 mesa > card and step direction control > > [EXTERNAL EMAIL] Be sure links are safe. > > Actually all I want to do is be able to home to index. Which I might be > able to do now. As my servo can output a encoder Z pulse. > > And I want to have linuxcnc remember where it is if I disable the servos. > That is now a massive deal but I get a bit sick of continously homing the > machine every time I push the E stop in and disable power to servos. It > would be nice to have the encoders still counting once the servos are > disabled. ( drives would still be on just not running a PID loop.) > > And yes I was wondering what trying to run a PID loop on a position servo > loop causes. > > Regards > > Andrew > > > > On Tue, Feb 11, 2020, 2:14 AM andy pugh <[email protected]> wrote: > > > On Mon, 10 Feb 2020 at 10:30, andrew beck <[email protected]> > > wrote: > > > On the back burner though I want to > > "close the loop" back into linuxcnc with a 7i84 mesa card I think. > > Has anyone done that before with a step direction control system? > > > > What do you anticipate gaining from bringing the encoders back to > LinuxCNC? > > > > If this is a stepper system (it's not clear without inbox-mining) then > > a PID will naturally attempt to run the motors faster, with the > > reverse of the hoped-for result. > > It is probably possible to simultaneously reduce the feed rate with > > adaptve feed and then attempt to recover the lost steps, but I don't > > know if anyone has tried that. > > > > If it is a step-servo system then the drives will already be doing all > > that they can. You won't gain much from bringing the motor encoder > > data in to LinuxCNC. > > However, you might be able to gain accuracy by adding linear scales to > > the system, and using the feedback from them to modify the motor > > position commands. > > > > -- > > 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 > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
