Dave wrote: > On 1/5/2010 11:49 AM, Flying Electron wrote: >> >> Since you have a mesa card, maybe you or anyone else that has a mesa >> card can explain how the servo PID works with the mesa in EMC. Does EMC >> do the PID calculations and just send a command to the mesa board or >> does the mesa board do the PID calculations and just tell EMC where the >> servo currently is? I guess another way to rephrase that is, is the >> mesa board closing the loop or does it need EMC to close the loop? > > As far as I know, all EMC2 servo solutions solve the motion PIDs within > the PC, not on any cards.
EMC2 can run either way - closing the servo loop on PC inside emc2, or letting the servo controller do it. Mesa cards (and other similar hardware) expose the servo encoder to emc2; emc2 does the PID calculation and computes a signed-magnitude motor control value; this gets fed to the motor amps. This is nice because you get full insight into what the motor is doing, and you can easily tune the PID controller. I dont know for sure, but I suspect that emc2's PID controller is better than most embedded solutions; it has first- and second-order feedforward etc. Gecko servo controllers (and other similar hardware) consume the servo encoder information; do their own PID calculation; and feed the motor the proper power. In this case, emc2 communicates only "desired position" information to the controller, usually via step/dir signals. This is nice because it makes it very simple to get the motor up and running. -- Sebastian Kuzminsky ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
