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extruder: Don't do pressure advance on velocity changes due to cornering 

Due to the lookahead, small changes in the direction of the toolhead
cause minor changes in toolhead velocity.  These "cornering" velocity
changes cause the current extruder code to trigger pressure advance
and its associated pressure retract.  This causes the extruder to
rapidly "jerk" the filament.

This code change updates the extruder to detect velocity changes due
solely to cornering and avoid pressure advance.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2016-11-04 22:43:50 -04:00
parent 93dd310add
commit 345fc41482
2 changed files with 9 additions and 9 deletions
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7
docs/Todo.md
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@ -150,13 +150,6 @@ Hardware features
Misc features
=============
* The "pressure advance" algorithm does improve extruder
functionality. However, it's interaction with lookahead is not ideal
as it can cause rapid jerks of the filament when the head speed
changes briefly during cornering. Ideally, pressure advance would
interact better with lookahead to avoid advance during transient
speed changes.
* Possibly use cubic functions instead of quadratic functions in step
compression code.

11
klippy/extruder.py
View File

@ -59,8 +59,15 @@ class PrinterExtruder:
prev_pressure_d += extra_accel_d
# Update decel and retract parameters when decelerating
if decel_t:
npd = move.end_v * move_extrude_r * self.pressure_advance
extra_decel_d = prev_pressure_d - npd
if move.corner_min:
npd = move.corner_max*move_extrude_r * self.pressure_advance
extra_decel_d = prev_pressure_d - npd
if move.end_v > move.corner_min:
extra_decel_d *= ((move.cruise_v - move.end_v)
/ (move.cruise_v - move.corner_min))
else:
npd = move.end_v * move_extrude_r * self.pressure_advance
extra_decel_d = prev_pressure_d - npd
if extra_decel_d > 0.:
extra_decel_v = extra_decel_d / decel_t
decel_v -= extra_decel_v