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.

-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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