Or to think of it another way, closing the loop with a force meter, would be analogous to the air regulator on an air counterbalance.
Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: Todd Zuercher <to...@pgrahamdunn.com> Sent: Thursday, September 19, 2019 8:32 AM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] ADC - realtime for load cell I don't think closing the loop with force feedback would work, If the motor is applying x amount of force, adding more weight isn't going to change the amount of force read by the force feedback device. It will just push it down. The feedback will only be reading the force applied by the motor to resist the load, not the load itself, so changing the load will only cause acceleration. Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: Chris Albertson <albertson.ch...@gmail.com> Sent: Wednesday, September 18, 2019 8:31 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] ADC - realtime for load cell One way to measure force is with a spring. Force is measured by looking at spring displacement. It is kind of like the load cell idea but you use a spring scale. Another way that is not quite to accurate is to measure the current in the motor. Current is proportional to torque. On Wed, Sep 18, 2019 at 4:39 PM Curtis Dutton <curtd...@gmail.com> wrote: > my experiment is to use a force measuring device to proportionally > control torque output on a servo attached to a ball screw. > > as a thought experiment imagine a platform hoisted by said ball screw. > as you added weight to the platform the motor torque would increase to > offset the weight and keep it steady. or you could set the required > force equal to X kgs and with less than X kgs on the platform it would > travel up proportionally. the motor would increase torque to maintain > the force value. if more force than X the platform would travel down > proportionally. > the motor would decrease torque to maintain the set force value. > > in effect not a position commanded but a force commanded linear actuator. > > is there some othere device that would be better for this type of > force measurement? in the 0 to about 500kg range. > > On Wed, Sep 18, 2019, 11:51 AM Chris Albertson > <albertson.ch...@gmail.com> > wrote: > > > in any case, even with lower 16-bit precision, the most important > > part of the design is the analog portion that sits between the load > > cell and the A/D converter. > > > > > > > > On Wed, Sep 18, 2019 at 6:38 AM Curtis Dutton <curtd...@gmail.com> > wrote: > > > > > Chris thanks for the info. > > > > > > I'm not exactly certain at this point what precision I need. I'll > > > be determining that experimentally later. I will keep in mind what > > > you > have > > > said, I'll deal with it after I get my hardware running. > > > > > > > > > On Tue, Sep 17, 2019 at 6:17 PM Chris Albertson < > > albertson.ch...@gmail.com > > > > > > > wrote: > > > > > > > If you want better than 16-bits and 1KHz then you also are going > > > > to > > need > > > a > > > > very good quality analog signal conditioning and instrumentation > > > amplifier. > > > > The analog circuit between the A/D converts and the load cell > really > > > does > > > > matter. You have to reject common-mode or the low bits will > just > > be > > > > filled with 60Hz noise. And you can not simply use a "brick wall" > > filter > > > > or you will not get the desired bandwidth through. (If you are > needing > > > to > > > > sample at 1K then you must care about 500Hz bandwidth. > > > > > > > > This matters a LOT more than which A/D chip you use. > > > > > > > > 22 bits is better than one part per million. Do you really need that? > > It > > > > will be hard to isolate all of the electrical and mechanical > > > > noise especially > > > > > > > > On Tue, Sep 17, 2019 at 2:26 PM Curtis Dutton > > > > <curtd...@gmail.com> > > > wrote: > > > > > > > > > I have a pet project I'm starting that will involve reading a > > > > > load > > cell > > > > in > > > > > as near as real time as possible and using that input for > > > > > servo > > > control. > > > > > > > > > > I plan on using mesa hardware to interface to the equipment. > > > > > Does > > > anyone > > > > > know of a nice way to interface hotsmot2 to a load cell? > > > > > > > > > > I would like a fairly high resolution. 16 bit minimum, the > > > > > higher > the > > > > > better up to 22 bit I suppose. As well as the ability to > > > > > sample at > > the > > > > > servo thread rate of 1 Khz. > > > > > > > > > > > > > > > Thanks, > > > > > Curtis > > > > > > > > > > _______________________________________________ > > > > > Emc-users mailing list > > > > > Emc-users@lists.sourceforge.net > > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > > > > > > > > -- > > > > > > > > Chris Albertson > > > > Redondo Beach, California > > > > > > > > _______________________________________________ > > > > Emc-users mailing list > > > > Emc-users@lists.sourceforge.net > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
