i have tryed this also u can get close u will not get Servo performance/position resolutions but u can get close.. hence why they say servo like on VFDs spec sheets
and it does make a big diff what level of VFD you use also some are alot better at this than others.. Yaskawa do some very clearver VFDs with Vector/servo like performance control techniques or Emerson in US also do very good drives there Unidrive model i think it is depends how big a VFD you need and if you already have motors etc i guess.. as when looking at more fancy spec VFDs price does come into play and servo setup can be had for same sort of price some times.. rob On 19/01/2012 00:40, Leonardo Marsaglia wrote: > Hello to everybody on this list. > > I've been working for almost two years with LinuxCNC software (the old EMC > hehe) and steppers driving an old Schaudt cam/lobe grinding machine. Now > it's time to improve the system and change the steppers for something with > more speed, specially for the Z axis. Anyway, the idea is to keep the costs > as low as possible. That's the main reason to not to use servo motors. > > A year ago more or less, Andy Pugh showed that it's not a crazy idea to use > a conventional three phase induction motor and a VFD in closed loop with > LinuxCNC software for positioning. Anyway, Andy told that his VFD was old, > and it couldn't respond well below 200 rpm. Nevertheless, the experiment > that Andy did, was really good and impressive. Here is a video of that > http://www.youtube.com/watch?v=3oTJNEVpvYY. > > My question is, what do you guys think, about using an induction motor, > reduced with worm and gear and driven by a vectorial VFD, (also there are > newer ones that apparently can keep full torque at zero speed), to drive a > joint and control position with minimum increments of about 100 pulses of > encoder (I'm planning to use an encoder of about 1000 pulses per turn). So > this would be 1/10 of a motor turn. > > Do you think this is achievable taking all of this in consideration?. I > mean, the reduction with worm and gear reduces the inertia factor almost to > nothing, so the deceleration of the motor would be practically > instantaneous. And also the motor would need to turn mostly at high speeds > because of the worm, even better if a use full torque at zero speed VFD. > > I hope you can help me with this, since the idea is not to risk too much > spending money on solutions that can't work at all. I'll ve very thanked if > you could guide me with this replacement. > > Thanks in advance as always for your help! > -- ------------------------------------------- Innovative-RC Website: www.innovative-rc.co.uk E-mail: sa...@innovative-rc.co.uk Ebay Shop: www.stores.ebay.co.uk/innovative-rc -------------------------------------------- ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
