From c3b1db31154b977d16fee91a756bb43b0f9575e9 Mon Sep 17 00:00:00 2001
From: Markus Quaritsch <markus.quaritsch@tugraz.at>
Date: Fri, 13 May 2016 09:31:48 +0200
Subject: [PATCH] simplified computation of average AirPowerLoss
---
.../Data/CrosswindCorrectionCdxALookup.cs | 20 +++++++------------
.../Data/CrosswindCorrectionVAirBeta.cs | 2 +-
.../Data/ICrossWindCorrection.cs | 2 +-
.../SimulationComponent/Impl/Vehicle.cs | 6 +++---
.../Simulation/MeasuredSpeedModeTest.cs | 12 +++++------
5 files changed, 18 insertions(+), 24 deletions(-)
diff --git a/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionCdxALookup.cs b/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionCdxALookup.cs
index 1a0977e7f8..d492bc5109 100644
--- a/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionCdxALookup.cs
+++ b/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionCdxALookup.cs
@@ -53,22 +53,16 @@ namespace TUGraz.VectoCore.Models.SimulationComponent.Data
public void SetDataBus(IDataBus dataBus) {}
- public Watt AverageAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2, Second dt)
+ public Watt AverageAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2)
{
var vAverage = (v1 + v2) / 2;
var cdA = EffectiveAirDragArea(vAverage);
- Watt averageAirDragPower;
- if (v1.IsEqual(v2)) {
- averageAirDragPower = (Physics.AirDensity / 2.0 * cdA * vAverage * vAverage * vAverage).Cast<Watt>();
- } else {
- // compute the average force within the current simulation interval
- // P(t) = k * CdA * v(t)^3 , v(t) = v0 + a * t // a != 0, P_avg = 1/T * Integral P(t) dt
- // => P_avg = (CdA * rho/2)/(4*a * dt) * (v2^4 - v1^4)
- var acceleration = (v2 - v1) / dt;
- averageAirDragPower =
- (Physics.AirDensity / 2.0 * cdA * (v2 * v2 * v2 * v2 - v1 * v1 * v1 * v1) / (4 * acceleration * dt)).Cast<Watt>();
- }
- return averageAirDragPower;
+
+ // compute the average force within the current simulation interval
+ // P(t) = k * CdA * v(t)^3 , v(t) = v0 + a * t // P_avg = 1/T * Integral P(t) dt
+ // => P_avg = (CdA * rho/2)/(4*a * dt) * (v2^4 - v1^4) // a = (v2-v1)/dt
+ // -> P_avg = (CdA * rho/2) * (v2^4 - v1^4) / (v2 - v1) = (CdA * rho/2) * (v1 + v2) * (v1^2 + v2^2)
+ return (Physics.AirDensity / (2.0 * 4) * cdA * (v1 + v2) * (v1 * v1 + v2 * v2)).Cast<Watt>();
}
protected internal SquareMeter EffectiveAirDragArea(MeterPerSecond x)
diff --git a/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionVAirBeta.cs b/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionVAirBeta.cs
index 58ff6a8531..b6627f1895 100644
--- a/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionVAirBeta.cs
+++ b/VectoCore/VectoCore/Models/SimulationComponent/Data/CrosswindCorrectionVAirBeta.cs
@@ -64,7 +64,7 @@ namespace TUGraz.VectoCore.Models.SimulationComponent.Data
get { return CrossWindCorrectionMode.VAirBetaLookupTable; }
}
- public Watt AverageAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2, Second dt)
+ public Watt AverageAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2)
{
if (DataBus == null) {
throw new VectoException("Databus is not set - can't access vAir, beta!");
diff --git a/VectoCore/VectoCore/Models/SimulationComponent/Data/ICrossWindCorrection.cs b/VectoCore/VectoCore/Models/SimulationComponent/Data/ICrossWindCorrection.cs
index 89d720a0e8..f664ebf1f2 100644
--- a/VectoCore/VectoCore/Models/SimulationComponent/Data/ICrossWindCorrection.cs
+++ b/VectoCore/VectoCore/Models/SimulationComponent/Data/ICrossWindCorrection.cs
@@ -43,6 +43,6 @@ namespace TUGraz.VectoCore.Models.SimulationComponent.Data
CrossWindCorrectionMode CorrectionMode { get; }
- Watt AverageAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2, Second dt);
+ Watt AverageAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2);
}
}
\ No newline at end of file
diff --git a/VectoCore/VectoCore/Models/SimulationComponent/Impl/Vehicle.cs b/VectoCore/VectoCore/Models/SimulationComponent/Impl/Vehicle.cs
index ccdb42b44a..6facbf6919 100644
--- a/VectoCore/VectoCore/Models/SimulationComponent/Impl/Vehicle.cs
+++ b/VectoCore/VectoCore/Models/SimulationComponent/Impl/Vehicle.cs
@@ -222,16 +222,16 @@ namespace TUGraz.VectoCore.Models.SimulationComponent.Impl
if (vAverage.IsEqual(0)) {
return 0.SI<Newton>();
}
- var result = ComputeAirDragPowerLoss(previousVelocity, previousVelocity + acceleration * dt, dt) /
+ var result = ComputeAirDragPowerLoss(previousVelocity, previousVelocity + acceleration * dt) /
vAverage;
Log.Debug("AirDragResistance: {0}", result);
return result;
}
- private Watt ComputeAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2, Second dt)
+ private Watt ComputeAirDragPowerLoss(MeterPerSecond v1, MeterPerSecond v2)
{
- return ModelData.CrossWindCorrectionCurve.AverageAirDragPowerLoss(v1, v2, dt);
+ return ModelData.CrossWindCorrectionCurve.AverageAirDragPowerLoss(v1, v2);
}
public class VehicleState
diff --git a/VectoCore/VectoCoreTest/Models/Simulation/MeasuredSpeedModeTest.cs b/VectoCore/VectoCoreTest/Models/Simulation/MeasuredSpeedModeTest.cs
index c73a60b201..0a380e6882 100644
--- a/VectoCore/VectoCoreTest/Models/Simulation/MeasuredSpeedModeTest.cs
+++ b/VectoCore/VectoCoreTest/Models/Simulation/MeasuredSpeedModeTest.cs
@@ -446,31 +446,31 @@ namespace TUGraz.VectoCore.Tests.Models.Simulation
dataBus.CycleData = new CycleData() { LeftSample = cycleEntry };
var pAvg =
- vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 20.KMPHtoMeterPerSecond(), 1.SI<Second>()).Value();
+ vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 20.KMPHtoMeterPerSecond()).Value();
Assert.AreEqual(509.259, pAvg, 1e-3);
pAvg =
- vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 21.KMPHtoMeterPerSecond(), 1.SI<Second>()).Value();
+ vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 21.KMPHtoMeterPerSecond()).Value();
Assert.AreEqual(521.990, pAvg, 1e-3);
pAvg =
- vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 30.KMPHtoMeterPerSecond(), 1.SI<Second>()).Value();
+ vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 30.KMPHtoMeterPerSecond()).Value();
Assert.AreEqual(636.574, pAvg, 1e-3);
cycleEntry.WindYawAngle = 20;
pAvg =
- vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 20.KMPHtoMeterPerSecond(), 1.SI<Second>()).Value();
+ vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 20.KMPHtoMeterPerSecond()).Value();
Assert.AreEqual(829.074, pAvg, 1e-3);
pAvg =
- vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 30.KMPHtoMeterPerSecond(), 1.SI<Second>()).Value();
+ vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 30.KMPHtoMeterPerSecond()).Value();
Assert.AreEqual(1036.343, pAvg, 1e-3);
cycleEntry.WindYawAngle = -120;
pAvg =
- vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 20.KMPHtoMeterPerSecond(), 1.SI<Second>()).Value();
+ vairbeta.AverageAirDragPowerLoss(20.KMPHtoMeterPerSecond(), 20.KMPHtoMeterPerSecond()).Value();
Assert.AreEqual(-1019.5370, pAvg, 1e-3);
}
}
--
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