Re: [Emc-users] variable reluctance motors
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 wrote: > > > --- On Fri, 5/3/13, N. Christopher Perry > wrote: > > > >> 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. > > > > > > 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
Re: [Emc-users] variable reluctance motors
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 wrote: > --- On Fri, 5/3/13, N. Christopher Perry wrote: > >> 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. > > > 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
Re: [Emc-users] variable reluctance motors
--- On Fri, 5/3/13, N. Christopher Perry wrote: > 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. 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
Re: [Emc-users] variable reluctance motors
Turns out that ripple compensation is very doable at steady speeds (which is why your new washing machine doesn't immediately shake itself to prices, where SR motors are most common these days) but is very hard to do in real-time at rapidly changing speeds, such as servoing applications. 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. There was a lot of thought put into trying to do ripple compensation at Otis Elevator when I was there. They care a lot about minimizing ripple torque given it very directly effects ride quality. In the end, proper motor architecture and design were identified as more effective at reducing torque ripple. I'm sure there is academic work being done to explore other potential control schemes, but none I've heard of solves these problems yet. N. Christopher Perry On May 3, 2013, at 5:15, Roland Jollivet wrote: > Ok, I did not know that. > I would think though, that ripple and resolution are software issues which > should be readily solvable for a particular motor with the complexity > afforded by micros today, and only needs to be done once. The material cost > savings though, accumulate. > > Regards > Roland > > > > On 2 May 2013 23:04, N. Christopher Perry wrote: > >> They have a lot of torque ripple and are harder to micro step. Given >> these factors their development is usually very targeted, so you won't >> generally find them lying about in surplus piles. >> >> For things like plasma and torch cutters they are probably a very cost >> effective alternative, if you can find them. >> >> N. Christopher Perry >> >> On May 2, 2013, at 14:38, Cogoman wrote: >> >>> I believe I have seen them used to advance the roller on an electric >> typewriter. When the current is off, there's no cogging like hybrid >> steppers have. That makes adjust paper height by hand seem normal for a >> typewriter. >>> Sent from my Kyocera Rise >>> >>> Roland Jollivet wrote: >>> Hi All Can anyone tell me if they are actually using variable reluctance >> motors as servos on CNC machines. I find it odd that such a simple motor is not in greater use. The only place I've ever seen them used was to position the head on old 8in >> floppy drives. Maybe they just don't have a good power to size ratio? Regards Roland >> -- Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 ___ 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 > -- > 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 troubleshoot
[Emc-users] variable reluctance motors
Ok, I did not know that. I would think though, that ripple and resolution are software issues which should be readily solvable for a particular motor with the complexity afforded by micros today, and only needs to be done once. The material cost savings though, accumulate. Regards Roland On 2 May 2013 23:04, N. Christopher Perry wrote: > They have a lot of torque ripple and are harder to micro step. Given > these factors their development is usually very targeted, so you won't > generally find them lying about in surplus piles. > > For things like plasma and torch cutters they are probably a very cost > effective alternative, if you can find them. > > N. Christopher Perry > > On May 2, 2013, at 14:38, Cogoman wrote: > > > I believe I have seen them used to advance the roller on an electric > typewriter. When the current is off, there's no cogging like hybrid > steppers have. That makes adjust paper height by hand seem normal for a > typewriter. > > Sent from my Kyocera Rise > > > > Roland Jollivet wrote: > > > >> Hi All > >> > >> Can anyone tell me if they are actually using variable reluctance > motors as > >> servos on CNC machines. > >> > >> I find it odd that such a simple motor is not in greater use. The only > >> place I've ever seen them used was to position the head on old 8in > floppy > >> drives. > >> Maybe they just don't have a good power to size ratio? > >> > >> Regards > >> Roland > >> > -- > >> Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET > >> Get 100% visibility into your production application - at no cost. > >> Code-level diagnostics for performance bottlenecks with <2% overhead > >> Download for free and get started troubleshooting in minutes. > >> http://p.sf.net/sfu/appdyn_d2d_ap1 > >> ___ > >> 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 > -- 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
Re: [Emc-users] variable reluctance motors
They have a lot of torque ripple and are harder to micro step. Given these factors their development is usually very targeted, so you won't generally find them lying about in surplus piles. For things like plasma and torch cutters they are probably a very cost effective alternative, if you can find them. N. Christopher Perry On May 2, 2013, at 14:38, Cogoman wrote: > I believe I have seen them used to advance the roller on an electric > typewriter. When the current is off, there's no cogging like hybrid steppers > have. That makes adjust paper height by hand seem normal for a typewriter. > Sent from my Kyocera Rise > > Roland Jollivet wrote: > >> Hi All >> >> Can anyone tell me if they are actually using variable reluctance motors as >> servos on CNC machines. >> >> I find it odd that such a simple motor is not in greater use. The only >> place I've ever seen them used was to position the head on old 8in floppy >> drives. >> Maybe they just don't have a good power to size ratio? >> >> Regards >> Roland >> -- >> Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET >> Get 100% visibility into your production application - at no cost. >> Code-level diagnostics for performance bottlenecks with <2% overhead >> Download for free and get started troubleshooting in minutes. >> http://p.sf.net/sfu/appdyn_d2d_ap1 >> ___ >> 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
Re: [Emc-users] variable reluctance motors
I believe I have seen them used to advance the roller on an electric typewriter. When the current is off, there's no cogging like hybrid steppers have. That makes adjust paper height by hand seem normal for a typewriter. Sent from my Kyocera Rise Roland Jollivet wrote: >Hi All > >Can anyone tell me if they are actually using variable reluctance motors as >servos on CNC machines. > >I find it odd that such a simple motor is not in greater use. The only >place I've ever seen them used was to position the head on old 8in floppy >drives. >Maybe they just don't have a good power to size ratio? > >Regards >Roland >-- >Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET >Get 100% visibility into your production application - at no cost. >Code-level diagnostics for performance bottlenecks with <2% overhead >Download for free and get started troubleshooting in minutes. >http://p.sf.net/sfu/appdyn_d2d_ap1 >___ >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
[Emc-users] variable reluctance motors
Hi All Can anyone tell me if they are actually using variable reluctance motors as servos on CNC machines. I find it odd that such a simple motor is not in greater use. The only place I've ever seen them used was to position the head on old 8in floppy drives. Maybe they just don't have a good power to size ratio? Regards Roland -- Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
