On 03/15/2014 04:44 PM, Peter Homann wrote: > Hi, > > If you are after closed loop spindle control for a KBIC style treadmill > controller a 5Hz PWM signal driving a PWM to analog converter is unlikely to > provide a satisfying result. Most close loop control systems use a 1KHz update > rate. You may get adequate results with a 100Hz update but 5Hz is too slow.
As a side note on KBIC controllers. I believe they have an analog feedback loop by sampling the forward voltage from the motor during the AC input zero crossing. Motor voltage = RPM. To me, its quite clever. I don't know if there are many analog designers any more, but I guess there is at least one. KB has a number of accessories available to go with the KBIC, so don't forget to check their website. (I have no connection to KB, but after studying the KBIC internals, I'm a bit of a fan) > Further to that, most converters including my DigiSpeeds filter the analog > output to smooth the control voltage. Also the KBIC controllers are also doing > the same thing resulting in a lag that will be hard to compensate for. Because the KBIC has an internal loop, if it works, it may not be worth fixing with another loop, but then again. Another thing, the KBIC is a Speed Controller as opposed to a servo drive that has four drive modes. It's really designed for applications that don't change speed or reverse quickly. It can be made to brake and reverse, but one is better off with a different drive for applications like rigid tapping. I think a Pico PWM drive might do nicely (but check with Jon on the filter caps and inductor heat for steady state applications). > That said you can have feedback that will help to maintain a constant speed > and correct the speed over a few seconds. Earlier Mach3 version had this > capability and it worked quite well. You could see the spindle speed creep up > to the set speed over a second or two. When the speed dropped as cutting > started, the speed would increase back to the set speed. > > Cheers, > > Peter Hey, Peter H. Glad to see that it seems you're doing well. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. Written by three acclaimed leaders in the field, this first edition is now available. Download your free book today! http://p.sf.net/sfu/13534_NeoTech _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
