On Sep 16 2013 11:04 AM, andy pugh wrote: > On 16 September 2013 17:49, Jon Elson <[email protected]> wrote: > >> 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. > > I don't think that is especially naïve, and I think is the basis of > the PVT trajectory scheme. > I think that your look-ahead only has to run as far ahead as the > current stopping distance, and then it propagates a modified speed > back up the chain.
I would add a little more time than that, but you and I are thinking along the same lines. The thing that got me thinking some time back was calculating how much you have to slow down when you have segments joining at different angles. If the lines are basically collinear, then you do not *have* to slow down. If they meet at say a 5 degree maybe a bit, and at 90, you nearly have to stop. It is calculating this that I find the most interesting... 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
