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toolhead: Limit lookahead optimization to moves with similar extrude ratios 

Only skip acceleration between moves if both moves perform a similar
amount of extrusion.  This ensures the extruder has sufficient time to
accelerate to and from each extrude move.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2016-07-12 12:04:06 -04:00
parent 589017a3d6
commit c847606311
1 changed files with 12 additions and 3 deletions
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15
klippy/toolhead.py
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@ -6,6 +6,8 @@
import math, logging, time import math, logging, time
import cartesian import cartesian
EXTRUDE_DIFF_IGNORE = 1.02
# Common suffixes: _d is distance (in mm), _v is velocity (in # Common suffixes: _d is distance (in mm), _v is velocity (in
# mm/second), _t is time (in seconds), _r is ratio (scalar between # mm/second), _t is time (in seconds), _r is ratio (scalar between
# 0.0 and 1.0) # 0.0 and 1.0)
@ -18,6 +20,7 @@ class Move:
self.move_d = move_d self.move_d = move_d
self.axes_d = axes_d self.axes_d = axes_d
self.accel = accel self.accel = accel
self.extrude_r = axes_d[3] / move_d
# Junction speeds are velocities squared. The junction_delta # Junction speeds are velocities squared. The junction_delta
# is the maximum amount of this squared-velocity that can # is the maximum amount of this squared-velocity that can
# change in this move. # change in this move.
@ -25,8 +28,14 @@ class Move:
self.junction_delta = 2.0 * move_d * accel self.junction_delta = 2.0 * move_d * accel
self.junction_start_max = 0. self.junction_start_max = 0.
def calc_junction(self, prev_move): def calc_junction(self, prev_move):
# Find max start junction velocity using approximated # Find max junction_start_velocity between two moves
# centripetal velocity as described at: if (self.extrude_r > prev_move.extrude_r * EXTRUDE_DIFF_IGNORE
or prev_move.extrude_r > self.extrude_r * EXTRUDE_DIFF_IGNORE):
# Extrude ratio between moves is too different
return
self.extrude_r = prev_move.extrude_r
# Find max velocity using approximated centripetal velocity as
# described at:
# https://onehossshay.wordpress.com/2011/09/24/improving_grbl_cornering_algorithm/ # https://onehossshay.wordpress.com/2011/09/24/improving_grbl_cornering_algorithm/
junction_cos_theta = -((self.axes_d[0] * prev_move.axes_d[0] junction_cos_theta = -((self.axes_d[0] * prev_move.axes_d[0]
+ self.axes_d[1] * prev_move.axes_d[1]) + self.axes_d[1] * prev_move.axes_d[1])
@ -34,7 +43,7 @@ class Move:
if junction_cos_theta > 0.999999: if junction_cos_theta > 0.999999:
return return
junction_cos_theta = max(junction_cos_theta, -0.999999) junction_cos_theta = max(junction_cos_theta, -0.999999)
sin_theta_d2 = math.sqrt(0.5*(1.0-junction_cos_theta)); sin_theta_d2 = math.sqrt(0.5*(1.0-junction_cos_theta))
R = self.toolhead.junction_deviation * sin_theta_d2 / (1. - sin_theta_d2) R = self.toolhead.junction_deviation * sin_theta_d2 / (1. - sin_theta_d2)
self.junction_start_max = min( self.junction_start_max = min(
R * self.accel, self.junction_max, prev_move.junction_max) R * self.accel, self.junction_max, prev_move.junction_max)