Hi Tomp, I understand the process and the step response. One thing in the mix that we haven't discussed, and I really was hoping Jon Elson would chime in again, is exactly how much impact the servo drive has on all this.
The application of DC voltage to a motor and then measuring up to speed brings up the question as to how you know the motor is up to speed. But anyway. Could do it with the scope monitoring step pulses and using evenly spaced pulses as the up to speed indication. But that's all empirical tested until it works. I want the starting point. John > -----Original Message----- > From: Thomas J Powderly [mailto:tjt...@gmail.com] > Sent: July-22-20 11:19 PM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with > Bostomatic BD18-2 to linuxcnc > > John > > We used to measure the acceleration rather than calculate it. > > > We loaded the axis with whatever tooling and 'normal' work piece, > > then,� in open loop, > > we applied a voltage that would achieve the max velocity, very briefly. > > just a bit longer than necc to get to the max velocity ( some hundred of > millisecond, not whole seconds ) > > then we measured how long it took to get to the max velocity > > _that_ is your practical acceleration in one direction > > the test is called a ';step' response > > it has nothing to do with stepper motors > > it has to do with the immediate 0 to max velocity command > > that's the 'step' > > on a dual trace storage scope you should monitor the velocity command > and the velocity. > > hth > > tomp > > ( this acc will be greater than the whole machine can achieve turning > sharp corners and reversing > > �but its a real, practical start value ) > > > On 7/23/20 12:57 PM, John Dammeyer wrote: > > Hi Chris, > > > >> -----Original Message----- > >> From: Chris Albertson [mailto:albertson.ch...@gmail.com] > >> > >> Why on Earth do people still use US units? OK if your final result must > >> be expressed that way, but do the math in metric then convert at the end. > > <SNIP> > >> I taught high school science for a while and never once would ever talk > >> about US units like feet or pints or pounds. The students had no problems > >> with this as their middle school teachers did the same. No one who is > >> educated in the last few decades would know how to work with "feet per > >> second squared" > >> > > Appreciate the comments. But even if I used the servo motor 1.6Nm the > > pitch of the lead screw is 0.2" so I could easily convert > that to 5.08mm or 0.00508m for that matter. In Canada much of what we do is > metric. And my program has a check box that lets > a user switch along with converting all the imperial units to metric and back. > > > > But that's beside the point I think. None of what you said explains how to > > calculate the MAX_ACCELERATION in the INI file given > parameters like motor/leadscrew torque, leadscrew pitch, max speed and table > weight (mass). > > > > Any ideas? > > John > > > > > > > > > >> 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 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
