The specification of velocities (and accelerations) is
confusing because of the multitude of ini settings available
in the [TRAJ], [AXIS_ll], [JOINTS_nn], and [DISPLAY] sections
of an ini file. Extra complications may occur because the
interpretation of items in the [DISPLAY] section may be
GUI-dependent.
Note that default values are silently applied (typically from
src/emc/nml_intf/emccfg.h) when not otherwise specified and
the defaults may not be applicable to a given machine. The
default values seem to be biased to machines with imperial units.
> Imho MAX_VELOCITY is the correct nomination, as a circular
> move may invoke several axis, is not linear
The axis letters X,Y,Z typically specify linear coordinates
and may be limited by trajectory planning according to
[TRAJ]MAX_LINEAR_VELOCITY.
For instance, in joints_axes branches, the velocity of a gcode
arc move (g2/g3) using x,y coordinates obeys the F number rate
OR is limited to the smallest value allowed by:
1) individual [AXIS_n]MAX_VELOCITY limits
or
2) [TRAJ]MAX_LINEAR_VELOCITY
or
3) feed override setting
or
4) maybe other items i don't know about
The [TRAJ]MAX_LINEAR_VELOCITY applies because a g2/g3 movement
is for linear coordinates (x,y,z).
If a rotary coordinate (typically A,B,C) is specified with g2
or g3, then the rotary travel is coordinated to end when the
x,y,z motion ends. As noted in the documentation for g2/g3,
"Lines of this sort are hardly ever programmed" It is more
common to use inverse feed rate mode (g94) when combining
linear and rotary moves.
To my knowledge, there is currently no non-gui code that uses
[TRAJ]MAX_ANGULAR_VELOCITY nor [TRAJ]DEFAULT_ANGULAR_VELOCITY:
$ cd my_git_root/src
$ find . -iname '*.*c' -exec grep -EH MAX_ANG\|DEFAULT_ANG {} \;
$ (nil)
The use of [TRAJ]MAX_LINEAR_VELOCITY and [TRAJ]DEFAULT_LINEAR_VELOCITY
was implemented long ago (cdc073dc6) in the joints_axes branch (I
suppose) as preparation for future inclusion of trajectory angular
coordinate settings should support for these be undertaken.
Accordingly, these future settings would be named
[TRAJ]MAX_ANGULAR_VELOCITY and [TRAJ]DEFAULT_ANGULAR_VELOCITY.
(Note, some guis do currently use [TRAJ]MAX_ANGULAR_VELOCITY and
[TRAJ]DEFAULT_ANGULAR_VELOCITY. For instance, the axis gui
uses these items as candidates for setting jog slider start
and limiting values.)
-----------------------------------------------------------------
I verified some comments above using a simple ngc file:
#<fcirclerate> = 10000
f10000
g0x10y0z0a0
f#<fcirclerate>
g2i-10 a100
g0x10y0z0
m2
and experimented with settings for #<fcirclerate> and the ini
settings for [TRAJ]MAX_LINEAR_VELOCITY and [AXIS_nn]MAX_VELOCITY.
For the ini items, it is convenient to use sim_pin, for example:
$ sim_pin ini.traj_max_velocity \
ini.x.max_velocity \
ini.y.max_velocity &
(Changes to ini.N.max_velocity values must be made when a
program is not running)
--
Dewey Garrett
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