Hi Leonardo. If you want to perform a closed loop position system as you said you need the inner speed closed loop. I do believe that can be quite difficult to perform both closed loops within LCNC with the expected accuracy. The VFD that you are using is a sensor less vector control type (that is why you have to close the speed loop outside the VFD). This kind of VFD are not the right product to run a "servo system" (as you already know) also because you should drive an asynchronous induction motor that is not usually suited for that porpouse. I'm not a LCNC guru .... but at least I've always used a vector VFD with encoder feedback tied from the motor to the VFD with the encoder simulation feedback connected to the axis module .
Alex On Wed, Mar 25, 2015 at 6:45 PM, Leonardo Marsaglia < leonardomarsagli...@gmail.com> wrote: > Hello to all! > > I just managed to turn the second motor of my machine (another AC motor > with a Powerflex 40 drive) and works just fine for positioning the part. > Tomorrow I'll be uploading some videos. > > Although I need to do some fine tuning on both the rotary and the linear > axis I was thinking about a concept to improve the accuracy of the servo > loops. > > As I have seen on many machines including the Mazak that we have here, the > servo systems close the velocity loop within the servo drive, and then the > CNC applies a voltage to control the velocity of the motor based on the PID > of the position loop. > > So as I see it, it's like there is one pid nested inside the other, or sort > of. Now the VFDs that I'm using can close the velocity loop but I would > have to use a special module for that. > > My question is, based on your experience. Could this improve the accuracy > of the joints? I guess this could be done within LinuxCNC without closing > the loop on the VFDs. > > Thanks as always for your help!! > > -- > *Leonardo Marsaglia*. > > ------------------------------------------------------------------------------ > Dive into the World of Parallel Programming The Go Parallel Website, > sponsored > by Intel and developed in partnership with Slashdot Media, is your hub for > all > things parallel software development, from weekly thought leadership blogs > to > news, videos, case studies, tutorials and more. Take a look and join the > conversation now. http://goparallel.sourceforge.net/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
