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 <[email protected]> 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 <[email protected]>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 <[email protected]> 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 <[email protected]> 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 >>>> [email protected] >>>> 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 >>> [email protected] >>> 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 >> [email protected] >> 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 > [email protected] > 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. 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