Partial dynamic brake bailoff

Dynamic brakes are complemented with air brakes proportionally to automatic brake demand

Author: cesarBLG

Source/Orts.Simulation/Simulation/RollingStocks/MSTSLocomotive.cs

@@ -372,6 +372,7 @@ public float OdometerM
         public float DynamicBrakeMaxCurrentA;
         public float DynamicBrakeDelayS;
         public bool DynamicBrakeAutoBailOff;
+        public bool DynamicBrakePartialBailOff;
         public bool UsingRearCab;
         public bool BrakeOverchargeSoundOn = false;
 
@@ -1019,6 +1020,7 @@ public override void Parse(string lowercasetoken, STFReader stf)
                 case "engine(dynamicbrakesmaximumforce": MaxDynamicBrakeForceN = stf.ReadFloatBlock(STFReader.UNITS.Force, null); break;
                 case "engine(dynamicbrakehasautobailoff":
                 case "engine(ortsdynamicbrakeshasautobailoff": DynamicBrakeAutoBailOff = stf.ReadBoolBlock(true); break;
+                case "engine(ortsdynamicbrakeshaspartialbailoff": DynamicBrakePartialBailOff = stf.ReadBoolBlock(false); break;
                 case "engine(dynamicbrakesdelaytimebeforeengaging": DynamicBrakeDelayS = stf.ReadFloatBlock(STFReader.UNITS.Time, null); break;
                 case "engine(dynamicbrakesresistorcurrentlimit": DynamicBrakeMaxCurrentA = stf.ReadFloatBlock(STFReader.UNITS.Current, null); break;
                 case "engine(numwheels": MSTSLocoNumDrvWheels = stf.ReadFloatBlock(STFReader.UNITS.None, 4.0f); if (MSTSLocoNumDrvWheels < 1) STFException.TraceWarning(stf, "Engine:NumWheels is less than 1, parts of the simulation may not function correctly"); break;
@@ -1138,6 +1140,7 @@ public override void Copy(MSTSWagon copy)
             ContinuousForceTimeFactor = locoCopy.ContinuousForceTimeFactor;
             DynamicBrakeForceCurves = locoCopy.DynamicBrakeForceCurves;
             DynamicBrakeAutoBailOff = locoCopy.DynamicBrakeAutoBailOff;
+            DynamicBrakePartialBailOff = locoCopy.DynamicBrakePartialBailOff;
             DynamicBrakeMaxCurrentA = locoCopy.DynamicBrakeMaxCurrentA;
             CombinedControlType = locoCopy.CombinedControlType;
             CombinedControlSplitPosition = locoCopy.CombinedControlSplitPosition;

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/Brakes/MSTS/AirSinglePipe.cs

@@ -561,9 +561,9 @@ public override void Update(float elapsedClockSeconds)
             }
             else
             {
+                bool isolateAutoBrake = false; 
                 if (Car is MSTSLocomotive loco && loco.EngineType != TrainCar.EngineTypes.Control)  // TODO - Control cars ned to be linked to power suppy requirements.
                 {
-                    bool isolateAutoBrake = false;
                     //    if (Car is MSTSLocomotive loco && loco.LocomotivePowerSupply.MainPowerSupplyOn)
                     if (loco.LocomotivePowerSupply.MainPowerSupplyOn)
                     {
@@ -588,20 +588,39 @@ public override void Update(float elapsedClockSeconds)
                         if (loco.DynamicBrakeAutoBailOff && loco.DynamicBrakePercent > 0 && Car.MaxBrakeForceN > 0)
                         {
                             var requiredBrakeForceN = Math.Min(AutoCylPressurePSI / MaxCylPressurePSI, 1) * Car.MaxBrakeForceN;
-                            var localBrakeForceN = loco.DynamicBrakeForceN + Math.Min(BrakeLine3PressurePSI / MaxCylPressurePSI, 1) * Car.MaxBrakeForceN;
+                            var localBrakeForceN = loco.DynamicBrakeForceN + Math.Min(CylPressurePSI / MaxCylPressurePSI, 1) * Car.MaxBrakeForceN;
                             if (localBrakeForceN > requiredBrakeForceN * 0.85f)
+                            {
                                 isolateAutoBrake = true;
+                                if (loco.DynamicBrakePartialBailOff)
+                                {
+                                    var compensatedPressurePSI = Math.Min(Math.Max((requiredBrakeForceN - loco.DynamicBrakeForceN)/Car.MaxBrakeForceN*MaxCylPressurePSI, 0), MaxCylPressurePSI);
+                                    if (CylPressurePSI < BrakeLine3PressurePSI)
+                                        CylPressurePSI = BrakeLine3PressurePSI;
+                                    if (compensatedPressurePSI < CylPressurePSI)
+                                    {
+                                        CylPressurePSI = Math.Max(CylPressurePSI - MaxReleaseRatePSIpS * elapsedClockSeconds, BrakeLine3PressurePSI);
+                                    }
+                                    else if (compensatedPressurePSI > CylPressurePSI + 4)
+                                    {
+                                        float dp = elapsedClockSeconds * MaxApplicationRatePSIpS;
+                                        if (BrakeLine2PressurePSI - dp * AuxBrakeLineVolumeRatio / AuxCylVolumeRatio < CylPressurePSI + dp)
+                                            dp = (BrakeLine2PressurePSI - CylPressurePSI) / (1 + AuxBrakeLineVolumeRatio / AuxCylVolumeRatio);
+                                        if (dp > compensatedPressurePSI - CylPressurePSI)
+                                            dp = compensatedPressurePSI - CylPressurePSI;
+                                        BrakeLine2PressurePSI -= dp * AuxBrakeLineVolumeRatio / AuxCylVolumeRatio;
+                                        CylPressurePSI += dp;
+                                    }
+                                }
+                                else
+                                {
+                                    CylPressurePSI = BrakeLine3PressurePSI;
+                                }
+                            }
                         }
                     }
-                    if (isolateAutoBrake)
-                        CylPressurePSI = BrakeLine3PressurePSI;
-                    else
-                        CylPressurePSI = Math.Max(AutoCylPressurePSI, BrakeLine3PressurePSI);
-                }
-                else
-                {
-                    CylPressurePSI = Math.Max(AutoCylPressurePSI, BrakeLine3PressurePSI);
                 }
+                if (!isolateAutoBrake) CylPressurePSI = Math.Max(AutoCylPressurePSI, BrakeLine3PressurePSI);
             }
 
             // During braking wheelslide control is effected throughout the train by additional equipment on each vehicle. In the piping to each pair of brake cylinders are fitted electrically operated