Gene, I would like to better understand your problem and have been thinking about this. I have some questions.
> > > > I don't think the fact that there is a worm gear matters. The problem, I > > bet is the large inertia of the system. > Hmm I am not sure about the inertia. I think if you have a large gear reduction then the inertia reflected across the gears should appear low from the motors point of view. > > > > Aside from proper tuning of the PID gains you could change the system to > > use a nested or "cascade" PID. THis allows the velocity setpoint to be > > controlled by the position error > > see the section "cascade" in the wiki article > > https://en.wikipedia.org/wiki/PID_controller > > > > I think you want a very fast loop i=for the inner PID. LIkely it > > wouldbe in external hardwarelike a microcontroller or FPGA. (does MESA > do > > the PID algorithm in the FPGA? It should.) > > > > > > > > On Sun, Sep 19, 2021 at 3:39 PM Gene Heskett <ghesk...@shentel.net> > wrote: > > > >> Greetings all; > >> As most of you know, I built a servo from scratch for a BS-1. > BS-1? What is this? Is this like a Grizzly BS-1 dividing head? Did you mount the servo motor to this? > >> > >> But I am not at all happy with its performance. > >> It is a motor with a worm output, driving the worm of the bs-1. And it > >> has an A/B quad encoder in it. > So you have a 2 worm gear reduction. Where in this system is the encoder mounted? What are the encoder counts per rev of the encoder? What are the motor characteristics? >> > >> But I must rather severely limit its run speed because the PID doesn't > >> see the null coming near fast enough to slow it and stop a couple > When you say null coming what do you mean? Is this the point where the desired position is reached according to the motion planner in LinuxCNC? > >> arcseconds early. I can't allow it to use reverse to stop as the motor > >> seems to be a near short circuit then, crowbarring the power supply, > How do you prevent the PWM from reversing the voltage on the motor? Is the motor driven from a PWM in only one polarity? How is the PWM and the switches arranged? Regards, John Figie _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
