> From: Gene Heskett [mailto:ghesk...@shentel.net] > On Friday 05 March 2021 18:59:19 John Dammeyer wrote: > > > net a-index-enable <=> pid.a.index-enable > > net a-enable => pid.a.enable > > net a-pos-cmd => pid.a.command > > #net a-vel-cmd => pid.a.command-deriv > > net a-pos-fb => pid.a.feedback > > net a-output => pid.a.output > > So this is a position servo. Very similar to mine currently. > I have an idb module which does an Inverse Dead Band between a-output and > the pwmgen.value, with the amount at 9.5, about 2 short of making it > hunt. > > That idb gives an offset in the currant value according to the direction, > which helps to cancel the brush and bearing friction. The pwmgen is > still pinging the driver about 7% when the motor has stopped. From > either direction. I need to set the DEADBAND accordingly, as the idb > module, when in balance would then shut the pwm off completely. That's > the theory anyway. > > Thanks John D. > Stay safe and well. > > Cheers, Gene Heskett
Hi Gene, I don't know if the following comments are helpful at all. I've found with the step and direction (250 lines per rev or 1000 pulses per rev) that when my servos stop that there is still a certain amount of 'looseness'. If I adjust parameters like P I can make it stiffer but then when it stops it's often noisy. Like it's trying to move one encoder edge but can't quite mechanically get there. Or over shoot perhaps? Then try to get back and friction too much. The Bergerda spindle did that when it stopped. I'd grab the spindle at the end of the quill and just twist it a bit and the squeal would stop. The Bergerda App Engineer told me what parameter to tweak and the noise and that issue went away. But it sounds like you have PWM from LinuxCNC and the encoder is fed back to LinuxCNC? Not that it should make any difference whether the controller is the PC or standalone like what's in the STMBL drive Andy and I have on our 4th Axis. Although, perhaps a question for Andy is whether he's running smart serial or step/dir and does LinuxCNC get the encoder information back from the STMBL? And does LinuxCNC do anything with that? Perhaps Andy can provide his STMBL 4th axis LinuxCNC HAL information and that might help you tune yours? More questions than answers. Sorry. John Dammeyer _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
