FTM_MINIMUM_CRUISE_RATIO

Marlin/Configuration_adv.h

@@ -1230,6 +1230,10 @@
     #define FTM_POLY6_ACCELERATION_OVERSHOOT 1.875f // Max acceleration overshoot factor for POLY6 (1.25 to 1.875)
   #endif
 
+  #define FTM_MINIMUM_CRUISE_RATIO 0.5f         // Minimum fraction of distance to spend at cruising speed (0.0f disables)
+                                                // Reduces vibrations and extrusion artefacts in short blocks like small surface
+                                                // features and thin solid infills
+
   /**
    * Advanced configuration
    */

Marlin/src/module/ft_motion/trajectory_trapezoidal.h

@@ -24,6 +24,10 @@
 #include "trajectory_generator.h"
 #include <math.h>
 
+#ifndef FTM_MINIMUM_CRUISE_RATIO
+  #define FTM_MINIMUM_CRUISE_RATIO 0
+#endif
+
 /**
  * Trapezoidal trajectory generator.
  * Provides continuous velocity, but acceleration is discontinuous.
@@ -41,10 +45,20 @@ class TrapezoidalTrajectoryGenerator : public TrajectoryGenerator {
     const float distance = distance_in;
     const float final_speed = final_speed_in; // just for consistency
 
-
     const float one_over_accel = 1.0f / acceleration;
     const float ldiff = distance + 0.5f * one_over_accel * (sq(initial_speed) + sq(final_speed));
 
+    if (FTM_MINIMUM_CRUISE_RATIO > 0) {
+      const float min_cruise_dist = distance * FTM_MINIMUM_CRUISE_RATIO;
+      const float max_nominal_from_ratio = (distance - min_cruise_dist) * acceleration
+                                           + 0.5f * (sq(initial_speed) + sq(final_speed));
+      float ratio_limited_speed = SQRT(max_nominal_from_ratio);
+      // Don’t allow it to go below endpoints (otherwise T1/T3 go negative)
+      const float v_floor = _MAX(initial_speed, final_speed);
+      NOLESS(ratio_limited_speed, v_floor);
+      NOMORE(nominal_speed, ratio_limited_speed);
+    }
+
     T2 = ldiff / nominal_speed - one_over_accel * nominal_speed;
     if (T2 < 0.0f) {
       T2 = 0.0f;