Dear Developers, mostly to Cradek:

The trajectory command for a circle is not really a circle. The higher
feedrate, the bigger the radial contour errors are.

When I run the G-code (feedrate=100mm/s, radius=40mm)
G2 x40 y0 i-40 j0 f6000,

I record the trajectory comands rx and ry from
axis.0.motor-pos-cmd
axis.1.motor-pos-cmd

then I calculate the contour error, i.e,
error=sqrt(rx*rx+ry*ry)-40

I found the reference input is a circle  with a slightly smaller
radius than the desired value (radius=40mm). Although these errors are
quite small for low feedrate (feedrate=20mm/s,  error=0.16 micron),
these errors are quite big for high feedrate (feedrate=100mm/s,
error=4 micron). We can imagine, with bigger radius and higher
feedrates, these errors will be even bigger. As the circular reference
inputs are calcuated from cosine and sine function, they should be
"perfect" with respect to the "float" type storage resolution in C.

Not sure whether anyone else found this. It would be great that
someone will help to fix this problem.

Best regards
Xuecheng

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