On Tue, 15 Apr 2008, John Kasunich wrote: > Date: Tue, 15 Apr 2008 21:58:45 -0400 > From: John Kasunich <[EMAIL PROTECTED]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: "Enhanced Machine Controller (EMC)" <[email protected]> > Subject: Re: [Emc-users] brushless motors > > Jon Elson wrote: >> Peter C. Wallace wrote: >>> If you are just driving a bare motor, try raising your sampling rate... >> Geez, the resonance seems to be about 40 Hz, my sampling rate is >> already 1 KHz, 25 X higher. But, yes, I can go to at least 5 >> KHz and see what happens. >> >> Jon >> > > Do you have current feedback or a current loop? (I doubt it.) If you > control current, you more-or-less eliminate one pole from the system > response. If you only control voltage, the system response is more > complex. Its pretty similar to the difference between current-mode and > voltage-mode control of switching power supplies. (see > http://encon.fke.utm.my/nikd/latest/OctCurrentMode.pdf) > > Regards, > > John Kasunich >
If you are used to brushed motors, AC servo motors typically have much higher inductance which will add more lag, especially if as JK says, you have voltage mode drive. Also you mentioned that you had some cogging. Is the resonance something that happens statically or only when moving at certain velocities? Is it possible that you have some non-linearity or even hysteresis in you drive - torque curve? To get our 3 phase driver to work well, we first had to first fix the VQ -> IQ nonlinearitys as best we could before closing the current loop. It was really lumpy at first... I wonder on a straight voltage mode drive, if you could have another feed forward term, kind of a high pass filter = derivative of requested torque, to counteract the delays cause by the motors inductance. > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by the 2008 JavaOne(SM) Conference > Don't miss this year's exciting event. There's still time to save $100. > Use priority code J8TL2D2. > 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 > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. 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
