Tests augmented.

src/main/java/org/openpnp/model/MotionProfile.java

@@ -491,6 +491,7 @@ public void solveProfile(final int iterations, final double vtol, final double t
             System.out.println("Vmax symmetrical move, immediate solution");
             return;
         }
+
         // Need to solve this numerically. Because the solution can have many roots and local minimae, we need to split it into multiple
         // regions with known qualities.
 
@@ -656,7 +657,7 @@ else if (t[5] > (-t[4]*0.25)) {
             if (sValid0 && sValid1 &&
                     Math.min(vEffEntry, vEffExit) <= vPeak0 
                     && Math.max(vEffEntry, vEffExit) >= vPeak1
-                    && vPeak0 != 0 && vPeak1 != 0) {
+                    /*&& vPeak0 != 0 && vPeak1 != 0*/) {
                 // We're between two valid entry/exit velocities. There may be an invalid region in the middle.
                 // --> Find it!
                 // Work hypothesis (from observing many curves empirically): 
@@ -680,16 +681,19 @@ else if (t[5] > (-t[4]*0.25)) {
                     tResult = time;
                     if (sResult < 0) {
                         // Great, we found it.
+                        System.out.println("    found invalid mid area "+vSearch+" s "+sResult+" t "+tResult);
                         break;
                     }
                     if (sResult > sSecant) {
                         // Raising result -> overshoot, this means there is no invalid section. 
+                        System.out.println("    overshot invalid mid area "+vSearch+" s "+sResult+" t "+tResult);
                         break;
                     }
                     // Apply secant method. 
                     double gradient = (sResult-sSecant)/(vSecant-vSearch);
                     if (Math.abs(gradient) < vttol) {
                         // Stuck in a local minimum. This must be a near miss situation (otherwise we should see overshoot).
+                        System.out.println("    stuck local minimum invalid mid area "+vSearch+" s "+sResult+" t "+tResult);
                         break;
                     }
                     double delta = -sResult/gradient;
@@ -745,6 +749,10 @@ else if (t[5] > (-t[4]*0.25)) {
             System.out.println("  re-establish");
             computeProfile(bestVelocity, vEffEntry, vEffExit, tMin);
         }
+        if (tMin > time - ttol) {
+            // The solver may have slightly approximated. Stretch the profile into the exact minimum time. 
+            retimeProfile(tMin);
+        }
         // Result is now stored in the profile i.e. you can get v[4], a[2], a[6] to get the (signed) solution.
         solvingTime = NanosecondTime.getRuntimeSeconds() - tStart;
         setOption(ProfileOption.Solved);
@@ -1317,9 +1325,6 @@ protected static boolean isCoordinated(MotionProfile[] profile1) {
 
     public void computeProfile(double vPeak, double vEffEntry, double vEffExit, double tMin) {
 
-        // Determine the direction of travel.
-        double signum = Math.signum(vPeak);
-
         // Compare effective entry/exit velocities to vMax to know whether we need to accelerate or decelerate on entry/exit.
         double signumEntry, signumExit;
         signumEntry = Math.signum(vPeak - vEffEntry);

src/test/java/AdvancedMotionTest.java

@@ -129,6 +129,12 @@ public void testMotionProfiles() throws Exception {
                 0.0, Double.POSITIVE_INFINITY, 0);
         testProfile("recheck solution", profile2);
 
+        // Impossible move.
+        profile = new MotionProfile(
+                20, 0, 0, -181.71043395996094, 0, 0,
+                0, 1000, 700, 2000, 2000, 15000, 0.277342, Double.POSITIVE_INFINITY, 0);
+        testProfile("Impossible move", profile);
+
         for (int s = -1; s <= 401; s++) {
             Double tf = profile.getForwardCrossingTime(s, true);
             Double tb = profile.getBackwardCrossingTime(s, true);