On Sep 16 2013 10:49 AM, Jon Elson wrote: > sam sokolik wrote: >> I think a larger read-ahead is the priority. >> > Yes, there are only two ways to deal with this. The safe way > requires the > interpreter to sanitize the tool path before handing it to the > trajectory planner, > so there will be no surprises while moving at high velocity.
this is the only safe way. > The other way is to assume the CAM system never generates code the > machine can't follow, and if it occurs, then you have a massive > velocity > discontinuity. This might make some people quite happy, as they > could > do high speed contouring that you can't do now with LinuxCNC. > But, of course, it is a bit dangerous, the "trust me, I know what I'm > doing" mode of operation. it might not be a commercial CAM operation, but hand written code, or something that is generated from a computer model that is never run through a proper CAM. > The problem with the "larger read-ahead" is that there is no best > choice for how much read-ahead you need, and doing it in real > time gets pretty complicated. It is conceivable that you could need > 1000 blocks of read ahead in some contouring programs, and I > don't think you can have the TP do this for every line and arc > segment. My naive scheme was to have a big buffer of the > trajectory moves, and when you hit a part that required slowing > down, you could then work backwards to figure out when you > needed to begin the slowing down. There would be a velocity > for each move, and this working backwards scheme would edit > those velocities down to accommodate the need for acceleration > in the future. Not sure if this makes sense, but that was what > seemed to be the mechanism that made the problem tractable > to me. it depends on where this happens. If it is on a PC, then remember memory is cheap as long as you use it reasonably (like dynamic memory allocation). It is likely that you can read the entire program in (even if it is 100's of thousands of blocks, and then analyze it. There will be natural breaks where the problem can be broken up (like tool changes), that could both reduce and complicate the analysis. EBo -- ------------------------------------------------------------------------------ LIMITED TIME SALE - Full Year of Microsoft Training For Just $49.99! 1,500+ hours of tutorials including VisualStudio 2012, Windows 8, SharePoint 2013, SQL 2012, MVC 4, more. BEST VALUE: New Multi-Library Power Pack includes Mobile, Cloud, Java, and UX Design. Lowest price ever! Ends 9/20/13. http://pubads.g.doubleclick.net/gampad/clk?id=58041151&iu=/4140/ostg.clktrk _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
