Stuart Stevenson wrote: > > > Gentlemen, > Thanks - Dave and Jon - just the info I was looking for. It looks > as if new amps will be cheaper-faster-better. Cheaper ? No. Faster? Quite likely. Better? If the Gettys amp is truly single phase, it is a disaster, and I think it would cause serious hair pulling to make it work with EMC. Any time the outer servo loop has more bandwidth than the inner loops, you get into maddening problems with the outer loops overcompensating and causing oscillation. With the bandwidth mismatch 100:1 the wrong way, I'd hate to see what would happen. > Jon, is it possible to parallel two of your amps to double their capacity? You are talking about the PWM servo amps? Hmmm, maybe. If you just ran the PWM and direction Opto's in series, the PWM controller should be able to drive them both. Or, it could drive the new version in parallel, as they need less current in the optos. Either way, that would have the PWM synchronized, and they each have their own current limiting, so they'd sort of share at their own limit points. I'd probably better try this here before I ship anything, but I believe that would work.
My PWM amps take a PWM signal as their input, and so you lose the velocity and torque loops of a true velocity servo amp. If the encoder has sufficient resolution, it is not a problem. If it is a lower resolution unit, then you will get step-wise motion at low speeds. I don't think you've worked with my PWM controller, just the PPMC. They are mostly similar, but the UPC is not modular like the PPMC. I have thought about making a new product that combines the analog velocity loop front end of my original analog velocity amp with the sign-magnitude PWM back end of my latest PWM servo amps. (That original velocity amp used synchronous antiphase PWM, and the output filters ran VERY hot! It had a few other problems as well.) I've never gotten the tuning of the thing as good as I'd like, there are some mechanical oscillatory poles in the system around 20 Hz that I've never been able to eliminate. If I damp the servo amplifier too much, then the EMC loops get unstable, if I damp less in the amplifier, then the mechanical resonances go wild. The thing is too close to the edge, and I've never been able to quite tame it. I probably just need to turn the gain down, but then the static error goes up, but maybe that is still small enough to be ignored. Anyway, that is just an idea, and I'd have to do serious testing before saying such a thing exists. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Register now and save $200. Hurry, offer ends at 11:59 p.m., Monday, April 7! Use priority code J8TLD2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
