To get higher accuracy you need more accurate measurement, some extra resolution above the accuracy is also useful.
For better dynamic perfomance it may make sense to close the inner loop if the inner loop is faster than the outer loop. If the electic response is much faster than the mechanical response then there is rather little to gain from faster control loop. If motor inductance is around 1mH, applied voltage is 48 volt and current is 10A then U=L*di/dt <=> dt = L*di/U = 1mH*10A/48V = 0.2ms = 200µs is the time to change motor torque from zero to maximum which put an upper limit on dynamic response, there is also a rotational speed dependent back emf reducing available voltage. If you do not like the math. Change servo loop peridicity adjust control loop and see if it make any real difference. Nicklas Karlsson On Wed, 25 Mar 2015 14:45:42 -0300 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
