W/ DQ control most of these problems become FAR simpler problems to deal with. But at that point you might as well go 'whole hog' and servo an induction motor. VR motors are attractive becasue they use cheap & simple controls. Once you need a real processor an induction machine does a better job once you accept it takes a little more math to control it. Google universial field oriented (UFO) control if anyone is more interested in it.
All motors have temperature, position, and flux level dependencies/non-linearities. But they can be fairly easily dealt w/ in the proper control. When we were doing ULTRA low slip induction motors drives we started w/ an extra loop of wire on the face of the poles to sense the gap flux. But the mathematical models of the motors were so good, calculated equaled measured and we did away w/ the extra expense of putting the windings in the motor and the ckts to measure them. And that was nearly 20yrs ago. I would have killed for the processors we use today;) SMD On Sat, May 4, 2013 at 2:01 AM, N. Christopher Perry < n_christopher_pe...@me.com> wrote: > As I said, trying to align injected harmonic content to a signal in > real-time with the required accuracy, while the fundamental frequency is > rapidly changing, is not algorithmically possible given existing control > schemes. Even if you could figure out how to fix that, no one has come up > with a way to evaluate the frequency content of a plant's response under > these conditions, so the controller does't have enough information to > calculate phase and magnitude information for that injected harmonic. It > doesn't matter how close you get the controller to the motor. > > Mapping schemes aren't terribly effective because torque ripple ends up > being dependent on more than just rotor position and torque. Temperature > dependencies in the permeability of the stator & rotor laminations, > localized saturation, positionally dependent gap variations all contribute > and more. > > If you figure out how, you could make a hell of a lot of money > > N. Christopher Perry > > On May 3, 2013, at 23:44, Gregg Eshelman <g_ala...@yahoo.com> wrote: > > > --- On Fri, 5/3/13, N. Christopher Perry <n_christopher_pe...@me.com> > wrote: > > <clip> > >> The main scheme for accomplishing ripple reduction is > >> harmonic injection, but that requires very accurate phase > >> and magnitude targets, both of which can be expected to > >> change as a function of speed and torque. Where speed > >> is changing, it's hard to even define phase in a control > >> space. > > <clip> > > > > How about building it into the motor? If it's going to be used as a > servo motor, it already has the setup to sense the RPM and velocity > changes. Should be possible to measure the torque in realtime too. > > > > Have all that connected into an on-motor power conditioning system that > gets instant feedback, modifying as required by external commands for > direction and speed changes. > > > > The thing could be programmed to emulate any kind of servo or stepper > and with the right sort of additional circuitry could run as an AC or DC > servo. > > > > That'd make those the first truly universal motors. > > > > > ------------------------------------------------------------------------------ > > Get 100% visibility into Java/.NET code with AppDynamics Lite > > It's a free troubleshooting tool designed for production > > Get down to code-level detail for bottlenecks, with <2% overhead. > > Download for free and get started troubleshooting in minutes. > > http://p.sf.net/sfu/appdyn_d2d_ap2 > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > ------------------------------------------------------------------------------ > Get 100% visibility into Java/.NET code with AppDynamics Lite > It's a free troubleshooting tool designed for production > Get down to code-level detail for bottlenecks, with <2% overhead. > Download for free and get started troubleshooting in minutes. > http://p.sf.net/sfu/appdyn_d2d_ap2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite It's a free troubleshooting tool designed for production Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
