total lookahead is a boundless problem, just as creating a 3d preview of the commanded toolpaths is a boundless problem (the backplot). the controller on some level can handle the ngc file in its entirety, so why not deal with machine acceleration limits on the same level, or machine limits in general - feed, movement bounds, spindle speeds, tool numbers, etc.
so commanded feedrates in a file are upper bounds, and within those bounds, maximum feedrates are always possible. --- On Fri, 4/20/12, Jon Elson <el...@pico-systems.com> wrote: > From: Jon Elson <el...@pico-systems.com> > Subject: Re: [Emc-users] Trajectory planning and other topics from a > EMC(LinuxCNC) newbie (TheNewbie) > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Date: Friday, April 20, 2012, 9:54 AM > andy pugh wrote: > > As I said earlier, I don't think this is a "Lookahead" > problem, it is > > a "must be able to stop inside the next code block" > problem. > > And I am not convinced that being able to stop the > machine within the > > next code block is necessarily a sensible requirement. > > > Exactly! It is a safe scheme, but becomes a > limitation. Total > lookahead is a boundless > problem, so I can see that is not sensible. What I can > imagine is a > method of lookahead > where each vector is examined for acceleration, and it keeps > running > ahead until a large > acceleration would be required. Some kind of mark is > made for that > vector so the > traj planner knows a deceleration would be required coming > up on that > point. Perhaps > this accel scanning could put the mark back the required > number of > blocks so that when > the traj planner hits that mark it begins the decel > then. This all is > complicated by the > feedrate override that is implemented at the moment. > But, the scanning > could probably > just assume 100% speed (or whatever the max override > allows). > > Jon > > ------------------------------------------------------------------------------ > For Developers, A Lot Can Happen In A Second. > Boundary is the first to Know...and Tell You. > Monitor Your Applications in Ultra-Fine Resolution. Try it > FREE! > http://p.sf.net/sfu/Boundary-d2dvs2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
