Changing the thresholds to be bigger in the previous patch isn't

really useful unless we simultaneously change the per-iteration deltas
to be smaller.  Add another pseudo-tunable to control the speed with
which we change values across iterations.  As it turns out, this is
much more effective than the threshold tunable.  It does come at the
cost of lower solution performance, however.

diff --git a/src/FDM/YASim/Airplane.cpp b/src/FDM/YASim/Airplane.cpp
index 05c64df319e4a9084d60afebb7a938adfa611c85..6f3b68a07e5a573b76509622f7e6e44385cf38d6 100644 (file)
--- a/src/FDM/YASim/Airplane.cpp
+++ b/src/FDM/YASim/Airplane.cpp
@@ -15,6 +15,18 @@ namespace yasim {
 inline float norm(float f) { return f<1 ? 1/f : f; }
 inline float abs(float f) { return f<0 ? -f : f; }
 
+// Solver threshold.  How close to the solution are we trying
+// to get?  Trying too hard can result in oscillations about
+// the correct solution, which is bad.  Stick this in as a
+// compile time constant for now, and consider making it
+// settable per-model.
+const float STHRESH = 1;
+
+// How slowly do we change values in the solver.  Too slow, and
+// the solution converges very slowly.  Too fast, and it can
+// oscillate.
+const float SOLVE_TWEAK = 0.3226;
+
 Airplane::Airplane()
 {
     _emptyWeight = 0;
@@ -787,7 +799,7 @@ void Airplane::runApproach()
 
 void Airplane::applyDragFactor(float factor)
 {
-    float applied = Math::sqrt(factor);
+    float applied = Math::pow(factor, SOLVE_TWEAK);
     _dragFactor *= applied;
     _wing->setDragScale(_wing->getDragScale() * applied);
     _tail->setDragScale(_tail->getDragScale() * applied);
@@ -804,7 +816,7 @@ void Airplane::applyDragFactor(float factor)
 
 void Airplane::applyLiftRatio(float factor)
 {
-    float applied = Math::sqrt(factor);
+    float applied = Math::pow(factor, SOLVE_TWEAK);
     _liftRatio *= applied;
     _wing->setLiftRatio(_wing->getLiftRatio() * applied);
     _tail->setLiftRatio(_tail->getLiftRatio() * applied);
@@ -929,13 +941,6 @@ void Airplane::solve()
        applyDragFactor(dragFactor);
        applyLiftRatio(liftFactor);
 
-       // Solver threshold.  How close to the solution are we trying
-       // to get?  Trying too hard can result in oscillations about
-       // the correct solution, which is bad.  Stick this in as a
-       // compile time constant for now, and consider making it
-       // settable per-model.
-       float STHRESH = 1.6;
-
        // DON'T do the following until the above are sane
        if(normFactor(dragFactor) > STHRESH*1.0001
           || normFactor(liftFactor) > STHRESH*1.0001)
@@ -944,8 +949,8 @@ void Airplane::solve()
        }
 
        // OK, now we can adjust the minor variables:
-       _cruiseAoA += 0.5f*aoaDelta;
-       _tailIncidence += 0.5f*tailDelta;
+       _cruiseAoA += SOLVE_TWEAK*aoaDelta;
+       _tailIncidence += SOLVE_TWEAK*tailDelta;
        
        _cruiseAoA = clamp(_cruiseAoA, -0.175f, 0.175f);
        _tailIncidence = clamp(_tailIncidence, -0.175f, 0.175f);
@@ -960,7 +965,7 @@ void Airplane::solve()
                 break;
 
             // Otherwise, adjust and do the next iteration
-            _approachElevator.val += 0.8 * elevDelta;
+            _approachElevator.val += SOLVE_TWEAK * elevDelta;
             if(abs(_approachElevator.val) > 1) {
                 _failureMsg = "Insufficient elevator to trim for approach";
                 break;