1. Configuring LinuxCNC
  3. Basic Configuration
  5. MAX_ACCELERATION value?

MAX_ACCELERATION value?

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18 Mar 2019 14:22 #128900 by dm17ry
MAX_ACCELERATION value? was created by dm17ry
using current 2.8.
it looks to me that the actual axis acceleration is limited to exactly half of the value specified in [AXIS_X]MAX_ACCELERATION. attached is a picture with waveforms where [AXIS_X]MAX_ACCELERATION = 50000 (mm/s/s), which results in joint.0.acc-cmd swing between 25000 and -25000. is this intended behavior? not clear from the documentation...
also i noticed that corresponding [JOINT_0]MAX_VELOCITY and [JOINT_0]MAX_ACCELERATION have no effect, at least with trivkins.
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18 Mar 2019 17:59 - 18 Mar 2019 20:01 #128913 by dgarrett
Replied by dgarrett on topic MAX_ACCELERATION value?
I could reproduce in a sim for some planned (gcode or mdi) moves.
For instance, a single g0 move with enough travel distance to reach
full speed shows this behavior.

I think it is built-in trajectory planning behavior for some moves as
set here:

github.com/LinuxCNC/linuxcnc/blob/master/src/emc/tp/tp.c#L328
Last edit: 18 Mar 2019 20:01 by dgarrett.

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19 Mar 2019 02:45 - 19 Mar 2019 03:35 #128957 by dm17ry
Replied by dm17ry on topic MAX_ACCELERATION value?
hm. it seems that it is not the full story... something pretty weird is happening on the last segment of the trajectory. code:

f100000
g0 x0
g1 x200 ; acc/dec get limited to 1/2 of max
g4 p0.2
g1 x300 ; max acc
g1 x400 ; max dec, then 1/2 acc (sic!) then 1/2 dec

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Last edit: 19 Mar 2019 03:35 by dm17ry.

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  1. Configuring LinuxCNC
  3. Basic Configuration
  5. MAX_ACCELERATION value?
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