On Saturday 25 January 2020 00:56:18 Chris Albertson wrote: > On Fri, Jan 24, 2020 at 8:29 PM Alan Condit <condit.a...@gmail.com> wrote: > > Chris, > > > > If I send 10000 steps to a smart X-axis controller, how does it stay > > in sync with a smart > > y-axis controller without someone controlling the synchronization > > between the two? > > As said, "steps" are the wrong thing to send. What they do is send > time, tagged points. Each point has a time tag on it. It is not > hard to synchronize clocks at the microsecond level. > > What they send is a list of target points. Assuming the machine > works in (x, y, z) space each point, you have "time", (x, y, z) and > (x', y', z') and (x'', y'', z''). A machine might have more or fewer > axis with different names, but same idea. Each controller can > handle up to some maximum number of axis and it wold not be until you > are over that limit that you'd have to split things. Doing six axis > on one controller is reasonable. > > The controller tries its best to hit the target points. It can happen > that a target is impossible. Also, some of ths data can be omitted. > Doing so wuld free the controller to do what it "wants". I think you > always want x,y,z but could maybe omit the prime (velocity) or double > prime (acceleration) This kind of path planning is what LinuxCNC > already does, but today it is reasonable to push this down into a $5 > chip. > > LinuxCNC is originally written used the exact oposite aproach and move > all the "smarts" upstream into a PC. > > The non-real-time part has to read the g-code or the conversational > interface or the hand pendant or video data and convert to a stream of > target points. > > That said, "steps" could work if each one had a time tag. But that > pushes the planning upstream and I think the better plan is to move as > much "smarts" as possible as close to the physical motor as possible. > So let the motor driver figure out what rate to drive each otor so > the targets are reached. > > Alan
I like this idea. But the com path must be two way so the planner can know if that target was reached for each time point, and must know also each axis;s limits for accel and top speed so the it can issue attainable targets. But wait, isn't that what lcnc is doing now? 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-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
