On Thursday 23 March 2017 07:01:19 MH wrote: > Hello Everybody, > > what Sebastian so eloquently described is what I originally meant, > however what the other people that replied added is also relevant I > think. The linear velocity phase results in a constant acceleration > that will have a Dirac delta function in its first order derivative, > and that is not desirable, due to the frequencies introduced. > > I must admit that my understanding of DC motor internals is somewhat > buried, also the last time I implemented a state control is 15y > ago...So I ll not follow up on these suggestions, although they would > probably tackle the problem at the root. > > Many years ago I implemented a sin^2(x) acceleration profile that was > jerk free, I wondered if anybody else had implemented such a thing in > the linuxcnc's TP. > Speaking from my electronics/broadcasting experience, where we have used a single sine^2(x) pulse as a general test signal for over 50 years, I can testify that if we had that in the tp, (and in the siggen module as a 4th choice of test signal shapes) it would be a most welcome addition to linuxcnc. That single pulse on line 19 during the old ntsc vertical interval, picked out and viewed by the trained eye on an oscilloscope tells us everything we need to know about how well our transmitters were tuned. With the added advantage of being able to fine tune the transmitter while broadcasting a normal programming schedule.
If contributed to linuxcnc, that would be a major improvement milestone for linuxcnc. > But using the feed forward terms is a very nice suggestion from Eric, > ty for that, I ll do that today. > > BR > Max. > > Am 22.03.2017 um 20:03 schrieb Sebastian Kuzminsky: > > On 03/22/2017 12:50 PM, Nicklas Karlsson wrote: > >>> Hello, > >>> > >>> I want to ask if anybody has worked on different acceleration > >>> profiles for linuxcnc ? I am looking for something that would > >>> remove the discontinuity in the first derivative of the > >>> acceleration ? > >>> > >>> BR > >>> Max. > >> > >> I guess to start with the DC motor model for example here > >> https://www.electrical4u.com/torque-equation-of-dc-motor/ would be > >> a good idea. Driving this with a limited voltage and current would > >> probably be a good model for the limitations. > > > > I think Max is asking about changes to the LinuxCNC trajectory > > planner that implement variable (non-constant) acceleration, aka > > "limited jerk". > > > > Currently when you start from a stand-still, command a move, and > > come to rest at the end of the move, LinuxCNC implements a > > trapezoidal velocity profile. This starts with a > > constant-acceleration phase until it reaches the maximum speed for > > the move, then enters a constant-velocity, zero-acceleration "cruise > > phase", and finishes with a > > constant-deceleration phase back to zero velocity. Each phase > > transition has an instant of infinite jerk, when acceleration goes > > from one constant value to another in a single motion cycle. > > > > I think Yishin Li (https://github.com/yishinli) has done some work > > in the area of jerk-limited trajectory planning, but AFAIK it has > > not shown up as a pull request to our repo yet. > > ---------------------------------------------------------------------- >-------- Check out the vibrant tech community on one of the world's > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
