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extruder: Don't assume start_v matches last end_v in pressure advance 

Due to minor differences in the extrude ratio, the last end velocity
of the filament may not exactly match the next move's start velocity
of the filament.  Implement more precise calculations for pressure
advance to take this into account.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2016-11-04 21:11:14 -04:00
parent a201385008
commit 93dd310add
1 changed files with 30 additions and 23 deletions
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53
klippy/extruder.py
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@ -44,38 +44,45 @@ class PrinterExtruder:
decel_v = cruise_v decel_v = cruise_v
# Update for pressure advance # Update for pressure advance
start_pos = self.extrude_pos
if (axis_d >= 0. and (move.axes_d[0] or move.axes_d[1]) if (axis_d >= 0. and (move.axes_d[0] or move.axes_d[1])
and self.pressure_advance): and self.pressure_advance):
# Increase accel_d and start_v when accelerating # Increase accel_d and start_v when accelerating
extra_accel_d = (cruise_v - start_v) * self.pressure_advance move_extrude_r = move.extrude_r
accel_d += extra_accel_d prev_pressure_d = start_pos - move.start_pos[3]
if accel_t: if accel_t:
start_v += extra_accel_d / accel_t npd = move.cruise_v * move_extrude_r * self.pressure_advance
extra_accel_d = npd - prev_pressure_d
if extra_accel_d > 0.:
accel_d += extra_accel_d
start_v += extra_accel_d / accel_t
prev_pressure_d += extra_accel_d
# Update decel and retract parameters when decelerating # Update decel and retract parameters when decelerating
if decel_t: if decel_t:
extra_decel_d = (cruise_v - end_v) * self.pressure_advance npd = move.end_v * move_extrude_r * self.pressure_advance
extra_decel_v = extra_decel_d / decel_t extra_decel_d = prev_pressure_d - npd
decel_v -= extra_decel_v if extra_decel_d > 0.:
end_v -= extra_decel_v extra_decel_v = extra_decel_d / decel_t
if decel_v <= 0.: decel_v -= extra_decel_v
# The entire decel phase is replaced with retraction end_v -= extra_decel_v
retract_t = decel_t if decel_v <= 0.:
retract_d = -(end_v + decel_v) * 0.5 * decel_t # The entire decel phase is replaced with retraction
retract_v = -decel_v retract_t = decel_t
decel_t = decel_d = 0. retract_d = -(end_v + decel_v) * 0.5 * decel_t
elif end_v < 0.: retract_v = -decel_v
# Split decel phase into decel and retraction decel_t = decel_d = 0.
retract_t = -end_v * inv_accel elif end_v < 0.:
retract_d = -end_v * 0.5 * retract_t # Split decel phase into decel and retraction
decel_t -= retract_t retract_t = -end_v * inv_accel
decel_d = decel_v * 0.5 * decel_t retract_d = -end_v * 0.5 * retract_t
else: decel_t -= retract_t
# There is still only a decel phase (no retraction) decel_d = decel_v * 0.5 * decel_t
decel_d -= extra_decel_d else:
# There is still only a decel phase (no retraction)
decel_d -= extra_decel_d
# Determine regular steps # Determine regular steps
forward_d = accel_d + cruise_d + decel_d forward_d = accel_d + cruise_d + decel_d
start_pos = self.extrude_pos
end_pos = start_pos + forward_d end_pos = start_pos + forward_d
inv_step_dist = self.stepper.inv_step_dist inv_step_dist = self.stepper.inv_step_dist
new_step_pos = int(end_pos*inv_step_dist + 0.5) new_step_pos = int(end_pos*inv_step_dist + 0.5)