On Friday 22 November 2019 18:50:39 Herzog Raoul wrote: > dear Gene, > > I agree with you, OpenCN is not meant for stepper motor applications, > since there is no feedback control using encoders. > And unmentioned, but even more important is the fact that what feedback we have is quantized at 10% of the rate you are achieving with ethercat running at 10 kilohertz.
That alone is a huge difference in the controlability of the system. I learned that lesson quickly when I replaced just the AB of an optical encoder (268 edges) on the spindle shaft of my G0704 with a 1000 line encoder (4000 edges) on the rear of the motor. That required "scale" changes driven by switches on the gear shift knob. It also took my PID Pgain from 3 to 40, but I run at 20 now. And the noise level that had me convinced I was about to tear it all down and replace all the $1 bearings with $20 ones, is completely gone. That's a 90 volt 9.7 amp at 1 hp rated motor, but the psu I built is much higher, but I am only aware I have pushed it too hard when rigid tapping with a big tap, when the pico system pwm-servo chirps the iron by going into its current limit at about 17 amps and 126 volts. Below that load limit, there is no slowdown or increase in mechanical noise. Its actually a bit startling to hear the chirp and understand why. Even the plastic gears are not complaining. I hope I can buy metal ones when they to strip out their hubs. If I still care. I am a retired television CE, a C.E.T. and now 85 yo, about to get a new aortic valve next month, this ones leaking back about 70%. That was this old mans education about what a hi-res encoder can do for control. Nothing short of amazing. > In my application I even use "dual feedback" with a rotary encoder on > the motor axis, AND a linear encoder for each axis ! I'm definitely > working in a high end appkication range, and it was my objective to > modify LinuxCNC for these high end applications. > And that it appears is exactly what you've done. > best regards, > > Raoul > > -----Message d'origine----- > De : Gene Heskett <[email protected]> > Envoyé : samedi 23 novembre 2019 00:36 > À : [email protected] > Objet : Re: [Emc-developers] announcement OpenCN, a new fork of > LinuxCNC --> Jerk control > > On Friday 22 November 2019 18:01:41 Herzog Raoul wrote: > > dear Nicklas, > > > > a given DC bus voltage for the drives is indeed *one* reason why the > > jerk *must* be limited, otherwise excessive tracking error occurs. > > But another reason for jerk control is to avoid machine vibration. > > > > best regards, > > > > Raoul > > This all sounds as if its is only applicable to servo systems, us > hobbyists with steppers running everything might as well sit back and > enjoy the "what ifs" since steppers have their own insurmountable jerk > problems when useing common $40 50 volt drivers, and mesa cards. > Watching your 5 axis work that block of brass is certainly a > revelation. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law > respectable. - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers > > > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
