This system http://www.automationtechnologiesinc .com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-kit/hybrid-servo-drive-kl-5080h
Is apparently a stepper motor that is controlled as a brushless. Essentially a stepper is a brushless. This needs a encoder, probably one with a index pulse correctly positioned, so that the electronics can compute the switching accurately. This means, even if the control of the drive looks like a STEP DIR control, internally there are position and current loops, theoretically such a drive could offer, velocity and current control (I've not checked for the above reference). This means essentially that, the motor runs cooler, because only the required intensity is flowing in the motor, and not the maximum required intensity (the one that is controlled with the typical potentiometer in typical stepper drives). This means as well that the motor runs smoother, this must be most noticeable at low velocities, and finally that the positioning can be as precise as the encoder is. I regard of precision, note that a stepper, is not as precise as 3600/steps_per_revolution/microsteps, because microsteps don need to be equally spaced, even steps are not precise due to manufacturing (magnetic field) do not have to be equally spaced. In addition to this forces make that the motor is not centered at the center of the microstep. In comparison a brushless type encoder based drive for steeper can be as precise as the encoder, you know the actual position with the encoder position, although the position can be different of the commanded position, but you know the difference. The only limitations seem to be related to control at hih rpms, performance degrades in comparison with brushless. I would say that this is related to the higher pole count of the steeper,and the inherent dificulty to stablish intensity at high pole conmutation frecuency due to impedance, something that con be alleviated increaing voltage as much as possible.. In regard to this the error position, it can be even smaller in this brushless system because, as it runs cooler, you can allow for small duration current higher than the nominal. For a steeper you can not surpass the nominal value, not for the motor not for the electronics. I've never run a system of this type, but I would love to use one of the MESA cards and brushless firmwares to test a such a setup (I'm interested in current control) if somebody with more experience thinks/knowns this is possible and not too difficult. Just using a double shaft stepper and a cheap encoder. I would love, to identify stepper cogging, and to software compensate for it. This said, if the proposed system works as theoretically expected, it looks to me it has a pretty reasonable price. Regard, Javier On Wed, Apr 10, 2013 at 6:45 AM, Viesturs Lācis <viesturs.la...@gmail.com>wrote: > 2013/4/10 Tomaz T. <tomaz_...@hotmail.com> > > > The whole point is that I don't have any feedback from steppers at this > > stage, and as I said, the "cheapest" solution would be to simply change > the > > existing one with the one with closed loop "future" (and also drivers). > So > > the basic idea might be to use In-Position signal (output) from stepper > > driver and when this goes fault, it triggers "following error" in > linuxcnc. > > Could this work? > > > > So why don't You put encoders on stepper motors and link encoder position > to axis.n.motor-pos-fb pin and let LinuxCNC track actual motor position and > it definitely will trigger following error, once it has been reached. This > way there are no fancy stepper drives and motors are required. > > > > > Anyone using this stepper system from kelinginc? > > > > > > > http://www.automationtechnologiesinc.com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-kit/hybrid-servo-drive-kl-5080h > > > No tuning of feedback loop? Well, then I do not see, how does this system > achieve its goal and correct for motor's position error. > > -- > Viesturs > > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > ------------------------------------------------------------------------------ > Precog is a next-generation analytics platform capable of advanced > analytics on semi-structured data. The platform includes APIs for building > apps and a phenomenal toolset for data science. Developers can use > our toolset for easy data analysis & visualization. Get a free account! > http://www2.precog.com/precogplatform/slashdotnewsletter > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Precog is a next-generation analytics platform capable of advanced analytics on semi-structured data. The platform includes APIs for building apps and a phenomenal toolset for data science. Developers can use our toolset for easy data analysis & visualization. Get a free account! http://www2.precog.com/precogplatform/slashdotnewsletter _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
