Fixed bug with incorrect heater feedforward when fan speed changes

4 files changed, 8 insertions, 8 deletions

diff --git a/src/Heating/FOPDT.cpp b/src/Heating/FOPDT.cpp
index 804eab14..2d83c4e8 100644
--- a/src/Heating/FOPDT.cpp
+++ b/src/Heating/FOPDT.cpp
@@ -298,15 +298,15 @@ void FopDt::CalcPidConstants(float targetTemperature) noexcept
 {
 	if (!pidParametersOverridden)
 	{
-		// Calculate the cooling rate per degC at this temperature. We assume the fan is off because that is the worst case i.e. longest time constant and less stable.
-		const float temperatureRise = targetTemperature - NormalAmbientTemperature;
+		// Calculate the cooling rate per degC at this temperature. We assume the fan is at 20% speed.
+		const float temperatureRise = max<float>(targetTemperature - NormalAmbientTemperature, 1.0);		// avoid division by zero!
 		const float averageCoolingRatePerDegC = GetCoolingRate(temperatureRise, 0.2)/temperatureRise;
 		loadChangeParams.kP = 0.7/(heatingRate * deadTime);
-		loadChangeParams.recipTi = powf(averageCoolingRatePerDegC, 0.25)/(1.14 * powf(deadTime, 0.75));	// Ti = 1.14 * timeConstant^0.25 * deadTime^0.75 (Ho et al)
+		loadChangeParams.recipTi = powf(averageCoolingRatePerDegC, 0.25)/(1.14 * powf(deadTime, 0.75));		// Ti = 1.14 * timeConstant^0.25 * deadTime^0.75 (Ho et al)
 		loadChangeParams.tD = deadTime * 0.7;
 
 		setpointChangeParams.kP = 0.7/(heatingRate * deadTime);
-		setpointChangeParams.recipTi = powf(averageCoolingRatePerDegC, 0.5)/powf(deadTime, 0.5);	// Ti = timeConstant^0.5 * deadTime^0.5
+		setpointChangeParams.recipTi = powf(averageCoolingRatePerDegC, 0.5)/powf(deadTime, 0.5);			// Ti = timeConstant^0.5 * deadTime^0.5
 		setpointChangeParams.tD = deadTime * 0.7;
 	}
 }
@@ -323,7 +323,7 @@ float FopDt::CorrectPwmForVoltage(float requiredPwm, float actualVoltage) const
 
 float FopDt::GetPwmCorrectionForFan(float temperatureRise, float fanPwmChange) const noexcept
 {
-	return temperatureRise * 0.01 * fanCoolingRate / heatingRate;
+	return temperatureRise * 0.01 * fanCoolingRate * fanPwmChange / heatingRate;
 }
 
 // Calculate the expected cooling rate for a given temperature rise above ambient
diff --git a/src/Heating/Heater.cpp b/src/Heating/Heater.cpp
index 5f02fa5e..ed868737 100644
--- a/src/Heating/Heater.cpp
+++ b/src/Heating/Heater.cpp
@@ -290,7 +290,7 @@ GCodeResult Heater::StartAutoTune(GCodeBuffer& gb, const StringRef& reply, FansB
 	tuningFans = fans;
 	tuningPwm = (gb.Seen('P')) ? gb.GetLimitedFValue('P', 0.1, 1.0) : GetModel().GetMaxPwm();
 	tuningHysteresis = (gb.Seen('Y')) ? gb.GetLimitedFValue('Y', 1.0, 20.0) : DefaultTuningHysteresis;
-	tuningFanPwm = (gb.Seen('F')) ? gb.GetLimitedFValue('F', 0.1, 1.0) : 1.0;
+	tuningFanPwm = (gb.Seen('F')) ? gb.GetLimitedFValue('F', 0.1, 1.0) : DefaultTuningFanPwm;
 
 	const GCodeResult rslt = StartAutoTune(reply, seenA, ambientTemp);
 	if (rslt == GCodeResult::ok)
diff --git a/src/Heating/Heater.h b/src/Heating/Heater.h
index 220164a4..28c27933 100644
--- a/src/Heating/Heater.h
+++ b/src/Heating/Heater.h
@@ -157,8 +157,8 @@ protected:
 	static constexpr unsigned int MinTuningHeaterCycles = 5;
 	static constexpr unsigned int MaxTuningHeaterCycles = 25;
 	static constexpr float DefaultTuningHysteresis = 5.0;
+	static constexpr float DefaultTuningFanPwm = 0.7;
 	static constexpr float TuningPeakTempDrop = 2.0;		// must be well below TuningHysteresis
-	static constexpr float FeedForwardMultiplier = 1.3;		// how much we over-compensate feedforward to allow for heat reservoirs during tuning
 	static constexpr float HeaterSettledCoolingTimeRatio = 0.93;
 
 	// Variables used during heater tuning
diff --git a/src/Heating/LocalHeater.cpp b/src/Heating/LocalHeater.cpp
index 8930c066..45c73d1a 100644
--- a/src/Heating/LocalHeater.cpp
+++ b/src/Heating/LocalHeater.cpp
@@ -557,7 +557,7 @@ void LocalHeater::FeedForwardAdjustment(float fanPwmChange, float extrusionChang
 {
 	if (mode == HeaterMode::stable)
 	{
-		const float boost = GetModel().GetPwmCorrectionForFan(GetTargetTemperature() - NormalAmbientTemperature, fanPwmChange) * FeedForwardMultiplier;
+		const float boost = GetModel().GetPwmCorrectionForFan(GetTargetTemperature() - NormalAmbientTemperature, fanPwmChange) * FanFeedForwardMultiplier;
 #if 0
 		if (reprap.Debug(moduleHeat))
 		{