Support non-Newtonian coolimg in heater model

Also record the long-term gain when tuning

9 files changed, 205 insertions, 116 deletions

diff --git a/src/CAN/CommandProcessor.cpp b/src/CAN/CommandProcessor.cpp
index e1d5ec23..b4816351 100644
--- a/src/CAN/CommandProcessor.cpp
+++ b/src/CAN/CommandProcessor.cpp
@@ -435,9 +435,9 @@ void CommandProcessor::ProcessReceivedMessage(CanMessageBuffer *buf) noexcept
 				rslt = reprap.GetHeat().FeedForward(buf->msg.heaterFeedForward, replyRef);
 				break;
 
-			case CanMessageType::updateHeaterModelNew:
-				requestId = buf->msg.heaterModelNew.requestId;
-				rslt = reprap.GetHeat().ProcessM307New(buf->msg.heaterModelNew, replyRef);
+			case CanMessageType::heaterModelNewNew:
+				requestId = buf->msg.heaterModelNewNew.requestId;
+				rslt = reprap.GetHeat().ProcessM307New(buf->msg.heaterModelNewNew, replyRef);
 				break;
 
 			case CanMessageType::setHeaterTemperature:
diff --git a/src/Heating/FOPDT.cpp b/src/Heating/FOPDT.cpp
index 22b3f414..4e75d534 100644
--- a/src/Heating/FOPDT.cpp
+++ b/src/Heating/FOPDT.cpp
@@ -8,7 +8,7 @@
 #include "FOPDT.h"
 
 #if HAS_MASS_STORAGE || HAS_SBC_INTERFACE
-# include "Storage/FileStore.h"
+# include <Storage/FileStore.h>
 #endif
 
 #if SUPPORT_CAN_EXPANSION
@@ -29,16 +29,17 @@ constexpr ObjectModelTableEntry FopDt::objectModelTable[] =
 {
 	// Within each group, these entries must be in alphabetical order
 	// 0. FopDt members
+	{ "coolingExp",			OBJECT_MODEL_FUNC(self->coolingRateExponent, 1),									ObjectModelEntryFlags::none },
 	{ "deadTime",			OBJECT_MODEL_FUNC(self->deadTime, 1),												ObjectModelEntryFlags::none },
 	{ "enabled",			OBJECT_MODEL_FUNC(self->enabled),													ObjectModelEntryFlags::none },
-	{ "gain",				OBJECT_MODEL_FUNC(self->GetGainFanOff(), 1),										ObjectModelEntryFlags::none },	// legacy, to be removed
+//	{ "gain",				OBJECT_MODEL_FUNC(self->GetGainFanOff(), 1),										ObjectModelEntryFlags::none },	// legacy, to be removed
 	{ "heatingRate",		OBJECT_MODEL_FUNC(self->heatingRate, 3),											ObjectModelEntryFlags::none },
 	{ "inverted",			OBJECT_MODEL_FUNC(self->inverted),													ObjectModelEntryFlags::none },
 	{ "maxPwm",				OBJECT_MODEL_FUNC(self->maxPwm, 2),													ObjectModelEntryFlags::none },
 	{ "pid",				OBJECT_MODEL_FUNC(self, 1),															ObjectModelEntryFlags::none },
 	{ "standardVoltage",	OBJECT_MODEL_FUNC(self->standardVoltage, 1),										ObjectModelEntryFlags::none },
-	{ "timeConstant",		OBJECT_MODEL_FUNC(self->GetTimeConstantFanOff(), 1),								ObjectModelEntryFlags::none },
-	{ "timeConstantFansOn",	OBJECT_MODEL_FUNC(self->GetTimeConstantFanOn(), 1),									ObjectModelEntryFlags::none },
+//	{ "timeConstant",		OBJECT_MODEL_FUNC(self->GetTimeConstantFanOff(), 1),								ObjectModelEntryFlags::none },	// legacy, to be removed
+//	{ "timeConstantFansOn",	OBJECT_MODEL_FUNC(self->GetTimeConstantFanOn(), 1),									ObjectModelEntryFlags::none },	// legacy, to be removed
 
 	// 1. PID members
 	{ "d",					OBJECT_MODEL_FUNC(self->loadChangeParams.tD * self->loadChangeParams.kP, 1),		ObjectModelEntryFlags::none },
@@ -48,7 +49,7 @@ constexpr ObjectModelTableEntry FopDt::objectModelTable[] =
 	{ "used",				OBJECT_MODEL_FUNC(self->usePid),													ObjectModelEntryFlags::none },
 };
 
-constexpr uint8_t FopDt::objectModelTableDescriptor[] = { 2, 10, 5 };
+constexpr uint8_t FopDt::objectModelTableDescriptor[] = { 2, 8, 5 };
 
 DEFINE_GET_OBJECT_MODEL_TABLE(FopDt)
 
@@ -57,17 +58,19 @@ DEFINE_GET_OBJECT_MODEL_TABLE(FopDt)
 // The heater model is disabled until the user declares the heater to be a bed, chamber or tool heater
 FopDt::FopDt() noexcept
 {
-	Clear();
+	Reset();
 }
 
 // Check the model parameters are sensible, if they are then save them and return true.
-bool FopDt::SetParameters(float phr, float pcrFanOff, float pcrFanOn, float pdt, float pMaxPwm, float temperatureLimit, float pVoltage, bool pUsePid, bool pInverted) noexcept
+bool FopDt::SetParameters(float phr, float pcrFanOff, float pcrFanOn, float pcrExponent, float pdt, float pMaxPwm, float temperatureLimit, float pVoltage, bool pUsePid, bool pInverted) noexcept
 {
 	// DC 2017-06-20: allow S down to 0.01 for one of our OEMs (use > 0.0099 because >= 0.01 doesn't work due to rounding error)
 	const float maxTempIncrease = max<float>(1500.0, temperatureLimit + 500.0);
 	if (   phr/pcrFanOff > 10.0						// minimum 10C temperature rise (same as with earlier heater model)
 		&& phr/pcrFanOff <= maxTempIncrease			// max temperature increase within limits
 		&& pcrFanOn >= pcrFanOff
+		&& pcrExponent >= 1.0
+		&& pcrExponent <= 1.6
 		&& pdt > 0.099
 		&& 0.5 >= pdt * pcrFanOn					// dead time less then cooling time constant
 		&& pMaxPwm > 0.0099
@@ -89,7 +92,7 @@ bool FopDt::SetParameters(float phr, float pcrFanOff, float pcrFanOn, float pdt,
 	return false;
 }
 
-void FopDt::Clear() noexcept
+void FopDt::Reset() noexcept
 {
 	SetDefaultToolParameters();						// set some values so that we don't report rubbish in the OM
 	enabled = false;								// heater is disabled until the parameters are set
@@ -102,6 +105,7 @@ void FopDt::SetDefaultToolParameters() noexcept
 	coolingRateFanOff = DefaultHotEndHeaterCoolingRate;
 	deadTime = DefaultHotEndHeaterDeadTime;
 	coolingRateChangeFanOn = 0.0;
+	coolingRateExponent = DefaultHotEndHeaterCoolingRateExponent;
 	maxPwm = 1.0;
 	standardVoltage = 0.0;
 	usePid = true;
@@ -117,6 +121,7 @@ void FopDt::SetDefaultBedOrChamberParameters() noexcept
 	coolingRateFanOff = DefaultBedHeaterCoolingRate;
 	deadTime = DefaultBedHeaterDeadTime;
 	coolingRateChangeFanOn = 0.0;
+	coolingRateExponent = DefaultBedHeaterCoolingRateExponent;
 	maxPwm = 1.0;
 	standardVoltage = 0.0;
 	usePid = false;
@@ -223,16 +228,80 @@ void FopDt::CalcPidConstants() noexcept
 	pidParametersOverridden = false;
 }
 
+// Adjust the actual heater PWM for supply voltage
+float FopDt::CorrectPwm(float requiredPwm, float actualVoltage) const noexcept
+{
+	if (requiredPwm < maxPwm && standardVoltage >= 10.0 && actualVoltage >= 10.0)
+	{
+		requiredPwm *= fsquare(standardVoltage/actualVoltage);
+	}
+	return max<float>(requiredPwm, maxPwm);
+}
+
+// Calculate the expected cooling rate for a given temperature rise abiie ambient
+float FopDt::GetCoolingRate(float temperatureRise, float fanPwm) const noexcept
+{
+	return coolingRateFanOff * powf(temperatureRise, coolingRateExponent) + temperatureRise * coolingRateChangeFanOn;
+}
+
+// Get an estimate of the expected heating rate at the specified temperature rise and PWM. The result may be negative.
+float FopDt::GetNetHeatingRate(float temperatureRise, float fanPwm, float heaterPwm) const noexcept
+{
+	return heatingRate * heaterPwm - GetCoolingRate(temperatureRise, fanPwm);
+}
+
+// Get an estimate of the heater PWM required to maintain a specified temperature
+float FopDt::EstimateRequiredPwm(float temperatureRise, float fanPwm) const noexcept
+{
+	return GetCoolingRate(temperatureRise, fanPwm)/heatingRate;
+}
+
 #if SUPPORT_CAN_EXPANSION
 
-void FopDt::SetupCanMessage(unsigned int heater, CanMessageUpdateHeaterModelNew& msg) const noexcept
+bool FopDt::SetParameters(const CanMessageHeaterModelNewNew& msg, float temperatureLimit) noexcept
+{
+	// DC 2017-06-20: allow S down to 0.01 for one of our OEMs (use > 0.0099 because >= 0.01 doesn't work due to rounding error)
+	const float maxTempIncrease = max<float>(1500.0, temperatureLimit + 500.0);
+	if (   msg.heatingRate/msg.coolingRate > 10.0									// minimum 10C temperature rise (same as with earlier heater model)
+		&& msg.heatingRate/msg.coolingRate <= maxTempIncrease						// max temperature increase within limits
+		&& msg.coolingRateChangeFanOn >= 0.0
+		&& msg.coolingRateExponent >= 1.0
+		&& msg.coolingRateExponent <= 1.6
+		&& msg.deadTime > 0.099
+		&& 0.5 >= msg.deadTime * (msg.coolingRate + msg.coolingRateChangeFanOn)		// dead time less then cooling time constant
+		&& msg.maxPwm > 0.0099
+		&& msg.maxPwm <= 1.0
+	   )
+	{
+		heatingRate = msg.heatingRate;
+		coolingRateFanOff = msg.coolingRate;
+		coolingRateChangeFanOn = msg.coolingRateChangeFanOn;
+		coolingRateExponent = msg.coolingRateExponent;
+		deadTime = msg.deadTime;
+		maxPwm = msg.maxPwm;
+		standardVoltage = msg.standardVoltage;
+		usePid = msg.usePid;
+		inverted = msg.inverted;
+		enabled = true;
+		CalcPidConstants();
+
+		if (msg.pidParametersOverridden)
+		{
+			SetRawPidParameters(msg.kP, msg.recipTi, msg.tD);
+		}
+		return true;
+	}
+	return false;
+}
+
+void FopDt::SetupCanMessage(unsigned int heater, CanMessageHeaterModelNewNew& msg) const noexcept
 {
 	msg.heater = heater;
 	msg.heatingRate = heatingRate;
 	msg.coolingRate = coolingRateFanOff;
 	msg.coolingRateChangeFanOn = coolingRateChangeFanOn;
 	msg.coolingRateChangeExtruding = 0.0;
-	msg.zero2 = 0.0;
+	msg.coolingRateExponent = coolingRateExponent;
 	msg.deadTime = deadTime;
 	msg.maxPwm = maxPwm;
 	msg.standardVoltage = standardVoltage;
diff --git a/src/Heating/FOPDT.h b/src/Heating/FOPDT.h
index e69c3ac6..9f39b301 100644
--- a/src/Heating/FOPDT.h
+++ b/src/Heating/FOPDT.h
@@ -34,7 +34,7 @@ class FileStore;
 #endif
 
 #if SUPPORT_CAN_EXPANSION
-struct CanMessageUpdateHeaterModelNew;
+struct CanMessageHeaterModelNewNew;
 #endif
 
 class FopDt INHERIT_OBJECT_MODEL
@@ -42,8 +42,8 @@ class FopDt INHERIT_OBJECT_MODEL
 public:
 	FopDt() noexcept;
 
-	void Clear() noexcept;
-	bool SetParameters(float phr, float pcrFanOff, float pcrFanOn, float pdt, float pMaxPwm, float temperatureLimit, float pVoltage, bool pUsePid, bool pInverted) noexcept;
+	void Reset() noexcept;
+	bool SetParameters(float phr, float pcrFanOff, float pcrFanOn, float pcrExponent, float pdt, float pMaxPwm, float temperatureLimit, float pVoltage, bool pUsePid, bool pInverted) noexcept;
 	void SetDefaultToolParameters() noexcept;
 	void SetDefaultBedOrChamberParameters() noexcept;
 
@@ -55,6 +55,12 @@ public:
 	float GetDeadTime() const noexcept { return deadTime; }
 	float GetMaxPwm() const noexcept { return maxPwm; }
 	float GetVoltage() const noexcept { return standardVoltage; }
+	float EstimateRequiredPwm(float temperatureRise, float fanPwm) const noexcept;
+	float GetCoolingRate(float temperatureRise, float fanPwm) const noexcept;
+	float GetNetHeatingRate(float temperatureRise, float fanPwm, float heaterPwm) const noexcept;
+	float CorrectPwm(float requiredPwm, float actualVoltage) const noexcept;
+	void AppendM307Command(unsigned int heaterNumber, const StringRef& str) const noexcept;
+	void AppendParameters(const StringRef& str) const noexcept;
 	bool UsePid() const noexcept { return usePid; }
 	bool IsInverted() const noexcept { return inverted; }
 	bool IsEnabled() const noexcept { return enabled; }
@@ -74,11 +80,12 @@ public:
 	}
 
 #if HAS_MASS_STORAGE || HAS_SBC_INTERFACE
-	bool WriteParameters(FileStore *f, size_t heater) const noexcept;		// erite the model parameters to file returning true if no error
+	bool WriteParameters(FileStore *f, size_t heater) const noexcept;		// write the model parameters to file returning true if no error
 #endif
 
 #if SUPPORT_CAN_EXPANSION
-	void SetupCanMessage(unsigned int heater, CanMessageUpdateHeaterModelNew& msg) const noexcept;
+	bool SetParameters(const CanMessageHeaterModelNewNew& msg, float temperatureLimit) noexcept;
+	void SetupCanMessage(unsigned int heater, CanMessageHeaterModelNewNew& msg) const noexcept;
 #endif
 
 protected:
@@ -90,6 +97,7 @@ private:
 	float heatingRate;
 	float coolingRateFanOff;
 	float coolingRateChangeFanOn;
+	float coolingRateExponent;
 	float deadTime;
 	float maxPwm;
 	float standardVoltage;					// power voltage reading at which tuning was done, or 0 if unknown
diff --git a/src/Heating/Heat.cpp b/src/Heating/Heat.cpp
index 2b2f361b..206e87e4 100644
--- a/src/Heating/Heat.cpp
+++ b/src/Heating/Heat.cpp
@@ -1418,10 +1418,10 @@ GCodeResult Heat::ConfigureHeater(const CanMessageGeneric& msg, const StringRef&
 	return h->ReportDetails(reply);
 }
 
-GCodeResult Heat::ProcessM307New(const CanMessageUpdateHeaterModelNew& msg, const StringRef& reply) noexcept
+GCodeResult Heat::ProcessM307New(const CanMessageHeaterModelNewNew& msg, const StringRef& reply) noexcept
 {
 	const auto h = FindHeater(msg.heater);
-	return (h.IsNotNull()) ? h->SetOrReportModelNew(msg.heater, msg, reply) : UnknownHeater(msg.heater, reply);
+	return (h.IsNotNull()) ? h->SetModel(msg.heater, msg, reply) : UnknownHeater(msg.heater, reply);
 }
 
 GCodeResult Heat::SetTemperature(const CanMessageSetHeaterTemperature& msg, const StringRef& reply) noexcept
diff --git a/src/Heating/Heat.h b/src/Heating/Heat.h
index 05232da5..8327f2a7 100644
--- a/src/Heating/Heat.h
+++ b/src/Heating/Heat.h
@@ -142,7 +142,7 @@ public:
 
 #if SUPPORT_REMOTE_COMMANDS
 	GCodeResult ConfigureHeater(const CanMessageGeneric& msg, const StringRef& reply) noexcept;
-	GCodeResult ProcessM307New(const CanMessageUpdateHeaterModelNew& msg, const StringRef& reply) noexcept;
+	GCodeResult ProcessM307New(const CanMessageHeaterModelNewNew& msg, const StringRef& reply) noexcept;
 	GCodeResult ProcessM308(const CanMessageGeneric& msg, const StringRef& reply) noexcept;
 	GCodeResult SetFaultDetection(const CanMessageSetHeaterFaultDetectionParameters& msg, const StringRef& reply) noexcept;
 	GCodeResult SetHeaterMonitors(const CanMessageSetHeaterMonitors& msg, const StringRef& reply) noexcept;
diff --git a/src/Heating/Heater.cpp b/src/Heating/Heater.cpp
index 19125f73..265912d4 100644
--- a/src/Heating/Heater.cpp
+++ b/src/Heating/Heater.cpp
@@ -173,7 +173,7 @@ GCodeResult Heater::SetOrReportModel(unsigned int heater, GCodeBuffer& gb, const
 	{
 		// Set the model
 		const bool inverseTemperatureControl = (inversionParameter == 1 || inversionParameter == 3);
-		const GCodeResult rslt = SetModel(heatingRate, coolingRates[0], coolingRates[1], td, maxPwm, voltage, dontUsePid == 0, inverseTemperatureControl, reply);
+		const GCodeResult rslt = SetModel(heatingRate, coolingRates[0], coolingRates[1], 1.0, td, maxPwm, voltage, dontUsePid == 0, inverseTemperatureControl, reply);
 		if (rslt <= GCodeResult::warning)
 		{
 			modelSetByUser = true;
@@ -213,10 +213,10 @@ GCodeResult Heater::SetOrReportModel(unsigned int heater, GCodeBuffer& gb, const
 }
 
 // Set the process model returning true if successful
-GCodeResult Heater::SetModel(float hr, float coolingRateFanOff, float coolingRateFanOn, float td, float maxPwm, float voltage, bool usePid, bool inverted, const StringRef& reply) noexcept
+GCodeResult Heater::SetModel(float hr, float coolingRateFanOff, float coolingRateFanOn, float coolingRateExponent, float td, float maxPwm, float voltage, bool usePid, bool inverted, const StringRef& reply) noexcept
 {
 	GCodeResult rslt;
-	if (model.SetParameters(hr, coolingRateFanOff, coolingRateFanOn, td, maxPwm, GetHighestTemperatureLimit(), voltage, usePid, inverted))
+	if (model.SetParameters(hr, coolingRateFanOff, coolingRateFanOn, coolingRateExponent, td, maxPwm, GetHighestTemperatureLimit(), voltage, usePid, inverted))
 	{
 		if (model.IsEnabled())
 		{
@@ -372,6 +372,7 @@ void Heater::CalculateModel(HeaterParameters& params) noexcept
 	params.deadTime = (((dHigh.GetMean() * tOff.GetMean()) + (dLow.GetMean() * tOn.GetMean())) * MillisToSeconds)/cycleTime;	// in seconds
 	params.coolingRate = coolingRate.GetMean()/averageTemperatureRiseCooling;			// in seconds
 	params.heatingRate = (heatingRate.GetMean() + (coolingRate.GetMean() * averageTemperatureRiseHeating/averageTemperatureRiseCooling)) / tuningPwm;
+	params.gain = (tOn.GetMean() + tOff.GetMean()) * averageTemperatureRiseHeating/tOn.GetMean();
 	params.numCycles = dHigh.GetNumSamples();
 }
 
@@ -397,6 +398,7 @@ void Heater::SetAndReportModel(bool usingFans) noexcept
 	String<StringLength256> str;
 	const GCodeResult rslt = SetModel(	hRate,
 										fanOffParams.coolingRate, fanOnCoolingRate,
+										1.0,
 										deadTime,
 										tuningPwm,
 #if HAS_VOLTAGE_MONITOR
@@ -408,7 +410,7 @@ void Heater::SetAndReportModel(bool usingFans) noexcept
 	if (rslt == GCodeResult::ok || rslt == GCodeResult::warning)
 	{
 		tuned = true;
-		str.printf("Auto tuning heater %u completed after %u idle and %u tuning cycles in %" PRIu32 " seconds. This heater needs the following M307 command:\n"
+		str.printf(	"Auto tuning heater %u completed after %u idle and %u tuning cycles in %" PRIu32 " seconds. This heater needs the following M307 command:\n"
 					" M307 H%u B0 R%.3f C%.1f",
 					GetHeaterNumber(),
 					idleCyclesDone,
@@ -422,6 +424,13 @@ void Heater::SetAndReportModel(bool usingFans) noexcept
 		}
 		str.catf(" D%.2f S%.2f V%.1f\n", (double)GetModel().GetDeadTime(), (double)GetModel().GetMaxPwm(), (double)GetModel().GetVoltage());
 		reprap.GetPlatform().Message(LoggedGenericMessage, str.c_str());
+		str.printf("Gain %.1f/%.1f", (double)fanOffParams.GetNormalGain(), (double)fanOffParams.gain);
+		if (usingFans)
+		{
+			str.catf(" : %.1f/.1%f", (double)fanOnParams.GetNormalGain(), (double)fanOnParams.gain);
+		}
+		str.cat('\n');
+		reprap.GetPlatform().Message(GenericMessage, str.c_str());
 		if (reprap.GetGCodes().SawM501InConfigFile())
 		{
 			reprap.GetPlatform().Message(GenericMessage, "Send M500 to save this command in config-override.g\n");
@@ -602,7 +611,7 @@ void Heater::SetTemperature(float t, bool activeNotStandby) THROWS(GCodeExceptio
 // This is called when config.g is about to be re-run
 void Heater::ClearModelAndMonitors() noexcept
 {
-	model.Clear();
+	model.Reset();
 	for (HeaterMonitor& hm : monitors)
 	{
 		hm.Disable();
@@ -647,14 +656,25 @@ GCodeResult Heater::SetHeaterMonitors(const CanMessageSetHeaterMonitors& msg, co
 	return GCodeResult::ok;
 }
 
-GCodeResult Heater::SetOrReportModelNew(unsigned int heater, const CanMessageUpdateHeaterModelNew& msg, const StringRef& reply) noexcept
+GCodeResult Heater::SetModel(unsigned int heater, const CanMessageHeaterModelNewNew& msg, const StringRef& reply) noexcept
 {
-	const GCodeResult rslt = SetModel(msg.heatingRate, msg.coolingRate, msg.coolingRateChangeFanOn, msg.deadTime, msg.maxPwm, msg.standardVoltage, msg.usePid, msg.inverted, reply);
-	if (msg.pidParametersOverridden && (rslt == GCodeResult::ok || rslt == GCodeResult::warning))
+	const float temperatureLimit = GetHighestTemperatureLimit();
+	const bool rslt = model.SetParameters(msg, temperatureLimit);
+	if (rslt)
 	{
-		SetRawPidParameters(msg.kP, msg.recipTi, msg.tD);
+		if (model.IsEnabled())
+		{
+			return UpdateModel(reply);
+		}
+		else
+		{
+			ResetHeater();
+		}
+		return GCodeResult::ok;
 	}
-	return rslt;
+
+	reply.copy("bad model parameters");
+	return GCodeResult::error;
 }
 
 GCodeResult Heater::SetTemperature(const CanMessageSetHeaterTemperature& msg, const StringRef& reply) noexcept
diff --git a/src/Heating/Heater.h b/src/Heating/Heater.h
index c9029ed4..699cf648 100644
--- a/src/Heating/Heater.h
+++ b/src/Heating/Heater.h
@@ -28,7 +28,7 @@ struct CanMessageHeaterTuningReport;
 struct CanHeaterReport;
 
 #if SUPPORT_REMOTE_COMMANDS
-struct CanMessageUpdateHeaterModelNew;
+struct CanMessageHeaterModelNewNew;
 struct CanMessageSetHeaterTemperature;
 struct CanMessageSetHeaterMonitors;
 struct CanMessageHeaterTuningCommand;
@@ -91,7 +91,7 @@ public:
 
 #if SUPPORT_REMOTE_COMMANDS
 	virtual GCodeResult TuningCommand(const CanMessageHeaterTuningCommand& msg, const StringRef& reply) noexcept = 0;
-	GCodeResult SetOrReportModelNew(unsigned int heater, const CanMessageUpdateHeaterModelNew& msg, const StringRef& reply) noexcept;
+	GCodeResult SetModel(unsigned int heater, const CanMessageHeaterModelNewNew& msg, const StringRef& reply) noexcept;
 	GCodeResult SetTemperature(const CanMessageSetHeaterTemperature& msg, const StringRef& reply) noexcept;
 	GCodeResult SetHeaterMonitors(const CanMessageSetHeaterMonitors& msg, const StringRef& reply) noexcept;
 #endif
@@ -119,7 +119,10 @@ protected:
 		float heatingRate;
 		float coolingRate;
 		float deadTime;
+		float gain;
 		unsigned int numCycles;
+
+		float GetNormalGain() const noexcept { return heatingRate/coolingRate; }
 	};
 
 	virtual void ResetHeater() noexcept = 0;
@@ -135,7 +138,7 @@ protected:
 	float GetMaxTemperatureExcursion() const noexcept { return maxTempExcursion; }
 	float GetMaxHeatingFaultTime() const noexcept { return maxHeatingFaultTime; }
 	float GetTargetTemperature() const noexcept { return (active) ? activeTemperature : standbyTemperature; }
-	GCodeResult SetModel(float hr, float coolingRateFanOff, float coolingRateFanOn, float td, float maxPwm, float voltage, bool usePid, bool inverted, const StringRef& reply) noexcept;
+	GCodeResult SetModel(float hr, float coolingRateFanOff, float coolingRateFanOn, float coolingRateExponent, float td, float maxPwm, float voltage, bool usePid, bool inverted, const StringRef& reply) noexcept;
 															// set the process model
 	void ReportTuningUpdate() noexcept;						// tell the user what's happening
 	void CalculateModel(HeaterParameters& params) noexcept;	// calculate G, td and tc from the accumulated readings
diff --git a/src/Heating/LocalHeater.cpp b/src/Heating/LocalHeater.cpp
index 52792069..6c8b4eae 100644
--- a/src/Heating/LocalHeater.cpp
+++ b/src/Heating/LocalHeater.cpp
@@ -349,103 +349,93 @@ void LocalHeater::Spin() noexcept
 			{
 				DoTuningStep();
 			}
+			else if (mode <= HeaterMode::suspended)
+			{
+				lastPwm = 0.0;
+			}
 			else
 			{
-				if (mode <= HeaterMode::suspended)
-				{
-					lastPwm = 0.0;
-				}
-				else
+				// Performing normal temperature control
+				if (GetModel().UsePid())
 				{
-					// Performing normal temperature control
-					if (GetModel().UsePid())
+					// Using PID mode. Determine the PID parameters to use.
+					const bool inLoadMode = (mode == HeaterMode::stable) || fabsf(error) < 3.0;		// use standard PID when maintaining temperature
+					const PidParameters& params = GetModel().GetPidParameters(inLoadMode);
+
+					// If the P and D terms together demand that the heater is full on or full off, disregard the I term
+					const float errorMinusDterm = error - (params.tD * derivative);
+					const float pPlusD = params.kP * errorMinusDterm;
+					const float expectedPwm = GetModel().EstimateRequiredPwm(temperature - NormalAmbientTemperature, 0.0);
+					if (pPlusD + expectedPwm > GetModel().GetMaxPwm())
 					{
-						// Using PID mode. Determine the PID parameters to use.
-						const bool inLoadMode = (mode == HeaterMode::stable) || fabsf(error) < 3.0;		// use standard PID when maintaining temperature
-						const PidParameters& params = GetModel().GetPidParameters(inLoadMode);
-
-						// If the P and D terms together demand that the heater is full on or full off, disregard the I term
-						const float errorMinusDterm = error - (params.tD * derivative);
-						const float pPlusD = params.kP * errorMinusDterm;
-						const float expectedPwm = constrain<float>((temperature - NormalAmbientTemperature)/GetModel().GetGainFanOff(), 0.0, GetModel().GetMaxPwm());
-						if (pPlusD + expectedPwm > GetModel().GetMaxPwm())
-						{
-							lastPwm = GetModel().GetMaxPwm();
-							// If we are heating up, preset the I term to the expected PWM at this temperature, ready for the switch over to PID
-							if (mode == HeaterMode::heating && error > 0.0 && derivative > 0.0)
-							{
-								iAccumulator = expectedPwm;
-							}
-						}
-						else if (pPlusD + expectedPwm < 0.0)
-						{
-							lastPwm = 0.0;
-						}
-						else
-						{
-							const float errorToUse = error;
-							iAccumulator = constrain<float>
-											(iAccumulator + (errorToUse * params.kP * params.recipTi * (HeatSampleIntervalMillis * MillisToSeconds)),
-												0.0, GetModel().GetMaxPwm());
-							lastPwm = constrain<float>(pPlusD + iAccumulator + extrusionBoost, 0.0, GetModel().GetMaxPwm());
-						}
-#if HAS_VOLTAGE_MONITOR
-						// Scale the PID based on the current voltage vs. the calibration voltage
-						if (lastPwm < 1.0 && GetModel().GetVoltage() >= 10.0)				// if heater is not fully on and we know the voltage we tuned the heater at
+						lastPwm = GetModel().GetMaxPwm();
+						// If we are heating up, preset the I term to the expected PWM at this temperature, ready for the switch over to PID
+						if (mode == HeaterMode::heating && error > 0.0 && derivative > 0.0)
 						{
-							if (!reprap.GetHeat().IsBedOrChamberHeater(GetHeaterNumber()))
-							{
-								const float currentVoltage = reprap.GetPlatform().GetCurrentPowerVoltage();
-								if (currentVoltage >= 10.0)				// if we have a sensible reading
-								{
-									lastPwm = min<float>(lastPwm * fsquare(GetModel().GetVoltage()/currentVoltage), 1.0);	// adjust the PWM by the square of the voltage ratio
-								}
-							}
+							iAccumulator = expectedPwm;
 						}
-#endif
+					}
+					else if (pPlusD + expectedPwm < 0.0)
+					{
+						lastPwm = 0.0;
 					}
 					else
 					{
-						// Using bang-bang mode
-						lastPwm = (error > 0.0) ? GetModel().GetMaxPwm() : 0.0;
+						const float errorToUse = error;
+						iAccumulator = constrain<float>
+										(iAccumulator + (errorToUse * params.kP * params.recipTi * (HeatSampleIntervalMillis * MillisToSeconds)),
+											0.0, GetModel().GetMaxPwm());
+						lastPwm = constrain<float>(pPlusD + iAccumulator + extrusionBoost, 0.0, GetModel().GetMaxPwm());
 					}
-
-					// Check if the generated PWM signal needs to be inverted for inverse temperature control
-					if (GetModel().IsInverted())
+#if HAS_VOLTAGE_MONITOR
+					// Scale the PID based on the current voltage vs. the calibration voltage
+					if (!reprap.GetHeat().IsBedOrChamberHeater(GetHeaterNumber()))
 					{
-						lastPwm = GetModel().GetMaxPwm() - lastPwm;
+						lastPwm = GetModel().CorrectPwm(lastPwm, reprap.GetPlatform().GetCurrentPowerVoltage());
 					}
+#endif
+				}
+				else
+				{
+					// Using bang-bang mode
+					lastPwm = (error > 0.0) ? GetModel().GetMaxPwm() : 0.0;
+				}
+
+				// Check if the generated PWM signal needs to be inverted for inverse temperature control
+				if (GetModel().IsInverted())
+				{
+					lastPwm = GetModel().GetMaxPwm() - lastPwm;
 				}
+			}
 
-				// Verify that everything is operating in the required temperature range
-				for (size_t i = 0; i < ARRAY_SIZE(monitors); ++i)
+			// Verify that everything is operating in the required temperature range
+			for (size_t i = 0; i < ARRAY_SIZE(monitors); ++i)
+			{
+				HeaterMonitor& prot = monitors[i];
+				if (!prot.Check())
 				{
-					HeaterMonitor& prot = monitors[i];
-					if (!prot.Check())
+					lastPwm = 0.0;
+					switch (prot.GetAction())
 					{
-						lastPwm = 0.0;
-						switch (prot.GetAction())
-						{
-						case HeaterMonitorAction::ShutDown:
-							reprap.GetHeat().SwitchOffAll(true);
-							reprap.GetPlatform().AtxPowerOff();
-							break;
+					case HeaterMonitorAction::ShutDown:
+						reprap.GetHeat().SwitchOffAll(true);
+						reprap.GetPlatform().AtxPowerOff();
+						break;
 
-						case HeaterMonitorAction::GenerateFault:
-							RaiseHeaterFault("Heater %u fault: heater monitor %u was triggered\n", GetHeaterNumber(), i);
-							break;
+					case HeaterMonitorAction::GenerateFault:
+						RaiseHeaterFault("Heater %u fault: heater monitor %u was triggered\n", GetHeaterNumber(), i);
+						break;
 
-						case HeaterMonitorAction::TemporarySwitchOff:
-							// Do nothing, the PWM value has already been set above
-							break;
+					case HeaterMonitorAction::TemporarySwitchOff:
+						// Do nothing, the PWM value has already been set above
+						break;
 
-						case HeaterMonitorAction::PermanentSwitchOff:
-							if (mode != HeaterMode::fault)
-							{
-								SwitchOff();
-							}
-							break;
+					case HeaterMonitorAction::PermanentSwitchOff:
+						if (mode != HeaterMode::fault)
+						{
+							SwitchOff();
 						}
+						break;
 					}
 				}
 			}
@@ -490,10 +480,9 @@ float LocalHeater::GetAveragePWM() const noexcept
 // Get a conservative estimate of the expected heating rate at the current temperature and average PWM. The result may be negative.
 float LocalHeater::GetExpectedHeatingRate() const noexcept
 {
-	const float initialHeatingRate = GetModel().GetHeatingRate() * min<float>(GetAveragePWM(), lastPwm);
-	return (temperature > LowAmbientTemperature)
-				? initialHeatingRate - (temperature - LowAmbientTemperature) * GetModel().GetCoolingRateFanOn()
-					: initialHeatingRate;
+	const float temperatureRise = max<float>(temperature - LowAmbientTemperature, 0.0);
+	const float pwm = min<float>(GetAveragePWM(), lastPwm);
+	return GetModel().GetNetHeatingRate(temperatureRise, 1.0, pwm);
 }
 
 // Auto tune this heater. The caller has already checked that no other heater is being tuned and has set up tuningTargetTemp, tuningPwm, tuningFans, tuningHysteresis and tuningFanPwm.
diff --git a/src/Heating/RemoteHeater.cpp b/src/Heating/RemoteHeater.cpp
index fe6932f7..215edb48 100644
--- a/src/Heating/RemoteHeater.cpp
+++ b/src/Heating/RemoteHeater.cpp
@@ -403,7 +403,7 @@ GCodeResult RemoteHeater::UpdateModel(const StringRef& reply) noexcept
 	if (buf != nullptr)
 	{
 		const CanRequestId rid = CanInterface::AllocateRequestId(boardAddress, buf);
-		CanMessageUpdateHeaterModelNew * const msg = buf->SetupRequestMessage<CanMessageUpdateHeaterModelNew>(rid, CanInterface::GetCanAddress(), boardAddress);
+		CanMessageHeaterModelNewNew * const msg = buf->SetupRequestMessage<CanMessageHeaterModelNewNew>(rid, CanInterface::GetCanAddress(), boardAddress);
 		GetModel().SetupCanMessage(GetHeaterNumber(), *msg);
 		return CanInterface::SendRequestAndGetStandardReply(buf, rid, reply);
 	}