toolhead: Replace max_accel_to_decel with minimum_cruise_ratio

The user facing max_accel_to_decel setting is complicated and
confusing.  Replace it with a new minimum_cruise_ratio parameter.
Internally this user-facing parameter will calculate the existing
low-level "accel_to_decel" mechanism.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 18 insertions, 7 deletions

diff --git a/docs/Config_Reference.md b/docs/Config_Reference.md
index 14b89200..1b833eaf 100644
--- a/docs/Config_Reference.md
+++ b/docs/Config_Reference.md
@@ -97,13 +97,22 @@ max_accel:
 #   will do so at the rate specified here. The value specified here
 #   may be changed at runtime using the SET_VELOCITY_LIMIT command.
 #   This parameter must be specified.
-#max_accel_to_decel:
-#   A pseudo acceleration (in mm/s^2) controlling how fast the
-#   toolhead may go from acceleration to deceleration. It is used to
-#   reduce the top speed of short zig-zag moves (and thus reduce
-#   printer vibration from these moves). The value specified here may
-#   be changed at runtime using the SET_VELOCITY_LIMIT command. The
-#   default is half of max_accel.
+#minimum_cruise_ratio: 0.5
+#   Most moves will accelerate to a cruising speed, travel at that
+#   cruising speed, and then decelerate. However, some moves that
+#   travel a short distance could nominally accelerate and then
+#   immediately decelerate. This option reduces the top speed of these
+#   moves to ensure there is always a minimum distance traveled at a
+#   cruising speed. That is, it enforces a minimum distance traveled
+#   at cruising speed relative to the total distance traveled. It is
+#   intended to reduce the top speed of short zigzag moves (and thus
+#   reduce printer vibration from these moves). For example, a
+#   minimum_cruise_ratio of 0.5 would ensure that a standalone 1.5mm
+#   move would have a minimum cruising distance of 0.75mm. Specify a
+#   ratio of 0.0 to disable this feature (there would be no minimum
+#   cruising distance enforced between acceleration and deceleration).
+#   The value specified here may be changed at runtime using the
+#   SET_VELOCITY_LIMIT command. The default is 0.5.
 #square_corner_velocity: 5.0
 #   The maximum velocity (in mm/s) that the toolhead may travel a 90
 #   degree corner at. A non-zero value can reduce changes in extruder
@@ -116,6 +125,8 @@ max_accel:
 #   decelerate to zero at each corner. The value specified here may be
 #   changed at runtime using the SET_VELOCITY_LIMIT command. The
 #   default is 5mm/s.
+#max_accel_to_decel:
+#   This parameter is deprecated and should no longer be used.
 ```
 
 ### [stepper]