Oh i didn't think about stepper. The equations are useful for DC, BLDC, PMSM, Asyncronous and probably also for switched reluctance.
On Sun, 19 Apr 2015 14:19:04 -0400 Gene Heskett <[email protected]> wrote: > On Sunday 19 April 2015 10:22:40 Karlsson & Wang wrote: > > Motor torque depends on current. Then increasing acceleration torque > > will also increase but how much depends on the inertia, there > > rotational inertia and the mass moved. It is also possible there are > > some viscous load which depend on speed of motion or rotational load. > > I assume current will increase but how much I have no idea. > > > > Electric motor generate a back EMF which depend on rotational speed so > > there is less voltage left to increase current/torque at high speed > > and more available voltage left to decrease speed. > > > > Here > > http://en.wikipedia.org/wiki/Brushed_DC_electric_motor#Torque_and_spee > >d_of_a_DC_motor the voltage balance and torque equations a little bit > > more than half way down in the document is incredibly good knowledge > > if working with servo motors. It is also useful to think about this > > equations then working with other types of electric motors. The > > equations are actually so important i think it would be a good idea to > > include them in the Linuxcnc manual maybe in the integrator chapter > > and I could provide some help if I have enough time. > > We are slightly at odds Nicklas. You are talking servo's correctly, and I > am talking steppers. These are different critters. > > The servo's you refer to will allow a small error and catch up when they > can, which may or may not wreck your part depending of the tolerances. > Steppers OTOH, will stall under the same conditions, wrecking the part > and likely breaking the tool too when the direction reverses at the end > of that move So one has to be quite considerably more cautious, even > paranoid, about how much you ask of them in the speed ranges where the > torque to stay precisely on the path may be iffy, particularly in a > complex part that may be quite a few loops thru the code to do the depth > the job needs. > > One of those consideration is available spindle horsepower, as in lack > thereof, its a 200 watt motor! I intend to switch it out at some point, > putting the 400 watter I took out of the lathe in its place, making it a > 2 speed range belt drive when I do, all of which I will have to design & > make. It, for some jobs, needs both 5x the rpms to get above any > framing resonances and a higher feed rate just to enhance the tool life > by cutting deeper into cooling wood when I am carving wood. The wood, > if the tool is sharp, doesn't burn, but the bit can turn straw colored > occassionaly. > > But thats off topic and I haven't really started on a design for that > yet. > > The higher voltage psu and a 5i25 card I just ordered are this springs > project. The motor is a different critter. > > > Regargs Nicklas Karlsson > > > > > > > > On Sun, 19 Apr 2015 05:55:31 -0400 > > > > Gene Heskett <[email protected]> wrote: > > > On Sunday 19 April 2015 02:58:14 Karlsson & Wang wrote: > > > > Increase in speed should almost certainly be 48/28 faster. I think > > > > this is true for acceleration to. Then you just have to hope for > > > > the electric motor to tolerate the higher voltage and for the > > > > mechanics to tolerate higher speed/acceleration. > > > > > > Humm, I would have to assume that since the motor currents would not > > > be similarly increased, that the accels, wouldn't be enhanced by > > > anywhere near that same ratio. > > > > > > The motors ultimate torque shouldn't change, just the speed at which > > > the torque falls off due to inductance? > > > > > > At present I do not believe the applied accels are modulated in the > > > TP to be slower at the higher motor speeds where torque is falling > > > off, so we need to use an accel it can handle in spite of the > > > falloff. This costs us time at the lower speeds where there is > > > generally plenty of torque. > > > > > > IMO, the accel should be applied with something that looks like a > > > t=rc time constant mapping, but that would not be optimum for the > > > needed decel since that would start a new t=rc curve, a fast slowing > > > at an rpm point where the torque is not available. > > > > > > Experimentally I have found I can move the existing setup at 22 ipm > > > in the range where table weights are well balanced if I use really > > > slow accels like 2 seconds or more to top speed. But for anything > > > like decent accel settings, I'll stall at 10 ipm or less so I > > > generally use sub 10 ipm moves now. One of the reasons for kicking > > > the motor voltage up closer to the limits of the drivers, 50 volts > > > in the case of the 2M542 driver. > > > > > > > Nicklas Karlsson > > > > > > Thanks Nicklas. At least I have a starting point now for how much > > > faster I can go. I got the new psu mounted with cooling arranged > > > yesterday, but not hooked up yet. > > > > > > Cheers, Gene Heskett > > > -- > > > "There are four boxes to be used in defense of liberty: > > > soap, ballot, jury, and ammo. Please use in that order." > > > -Ed Howdershelt (Author) > > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > > > -------------------------------------------------------------------- > > >---------- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM > > > EDT Develop your own process in accordance with the BPMN 2 standard > > > Learn Process modeling best practices with Bonita BPM through live > > > exercises > > > http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- > > > event?utm_ > > > source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_ > > >SF _______________________________________________ > > > Emc-users mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > ---------------------------------------------------------------------- > >-------- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT > > Develop your own process in accordance with the BPMN 2 standard > > Learn Process modeling best practices with Bonita BPM through live > > exercises > > http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- > > event?utm_ > > source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > Genes Web page <http://geneslinuxbox.net:6309/gene> > > ------------------------------------------------------------------------------ > BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT > Develop your own process in accordance with the BPMN 2 standard > Learn Process modeling best practices with Bonita BPM through live exercises > http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ > source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15&utm_medium=email&utm_campaign=VA_SF _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
