On Wed, Mar 3, 2010 at 2:01 AM, Chris Morley <[email protected]>wrote:
> > > > Judging from the traces, I suspect you have velocity mode servo amps, > > > and I suspect their velocity loops aren't tuned. It doesn't make > > > sense to tune EMC's position loop when the drive velocity loop isn't > > > right - the position loop builds on the foundation provided by the > > > drive. > > > > > > If you can tell us about your drives (and ideally post a link to a > > > copy of the drive manual and/or specs), we can probably help more. > > > > > > > The servo drives are from Advanced Motion Controls. They are Direct PWM > > Brushless DC Servo Drives Model# BD30A8. The datasheet can be read at > > http://www.a-m-c.com/download/datasheet/bd30a8.pdf . I talked to their > tech > > support and there is no current loop or velocity loop in the drive. They > > told me the PWM signal directly controls the amount of time the MOSFETs > are > > turned on. If it was a brushed DC motor, I understand that the PWM duty > > cycle would have a linear relationship to the average voltage and hence > > average speed of the motor, but since it's a brushless DC motor, I don't > > understand if that same relationship holds or not. > > > > > AMC has instructions on their web site (little hard to find the right one) > > on how to tune the servo drive itself. > > Are you sure the drive is set right for velocity mode? > > From my understanding the drives don't have a velocity mode or a current mode. The PWM signal directly turns the MOSFETS on and off. I've set up the servo PID loop with a Pgain of 2, some FF1 and FF2 and it's gotten good enough to position the machine where it needs to be. I was way off with the Pgain of 8 that I started with. Thanks everyone for all your help! Lawrence ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
