there is a limitation of 'too short' Rob explained it in a dev email
(discusing the Q part of G64)..
Unfortunately, the new TP still has the restriction that you have to touch
each segment at least once. A small NCD tolerance is still useful to
combine stupidly short segments, in particular ones that would be skipped
over in a single cycle of the trajectory planner.
A quick theoretical example: If we want to follow a path at 60 IPM (1 IPS),
with a servo rate of 1kHz, then a segment that is shorter than 0.001" could
be skipped entirely during a single cycle update. Therefore, an NCD
tolerance of roughly 0.001" would eliminate these very short segments,
letting the TP maintain the desired speed.
Given this benefit, I don't think we can totally eliminate it. However,
since the tolerance can be much smaller than the blend tolerance and still
work well, it seems to me like another argument to decouple them.
-Rob
sam
On 03/21/2014 01:31 PM, Bertho Stultiens wrote:
> On 03/21/2014 07:06 PM, sam sokolik wrote:
>> I was wondering how I could check that.. I don't know - but I can tell
>> you this..
>> At G64p.002q0
>> P is in mm and my config. 30in/s^2 and 500ipm per axis..
>> the velocity just starts to dip - just wiggles between 3000 and
>> 2999mm/min. If I do p.001q0 it fluxuates around 2200mm/min. The
>> accelleration graph looks a but harry at that thoug though.. (wipping
>> around to try to keep up the path tolerance and velocity up..)
> [snip]
>> so with the path programmed - it can follow at cutting speed with
>> tollerances below what is sane... (with that config)
> That looks pretty impressive to follow within 50 micrometer. I prepared
> a few versions of the same patters. Each with a different angular
> interval to generate the curve from 10deg...0.2deg steps. That results
> in linear segments with lengths from ~0.75mm to ~0.01mm.
>
> http://media.vagrearg.org/gcmc/trochoidal-steps.tar.gz
>
> I wonder if the smallest angular interval would improve the following
> and where the breakdown occurs.
>
>
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