Add injector model class (#1687)

* stub injector model

* tests

Co-authored-by: Matthew Kennedy <makenne@microsoft.com>

firmware/controllers/algo/algo.mk

@@ -17,3 +17,4 @@ CONTROLLERS_ALGO_SRC_CPP = $(PROJECT_DIR)/controllers/algo/advance_map.cpp \
 	$(PROJECT_DIR)/controllers/algo/airmass/speed_density_airmass.cpp \
 	$(PROJECT_DIR)/controllers/algo/airmass/speed_density_base.cpp \
 	$(PROJECT_DIR)/controllers/algo/fuel/fuel_computer.cpp \
+	$(PROJECT_DIR)/controllers/algo/fuel/injector_model.cpp \

firmware/controllers/algo/fuel/injector_model.cpp

@@ -0,0 +1,35 @@
+#include "injector_model.h"
+
+EXTERN_ENGINE;
+
+void InjectorModelBase::prepare() {
+	m_massFlowRate = getInjectorMassFlowRate();
+	m_deadtime = getDeadtime();
+}
+
+constexpr float convertToGramsPerSecond(float ccPerMinute) {
+	float ccPerSecond = ccPerMinute / 60;
+	return ccPerSecond * 0.72f;	// 0.72g/cc fuel density
+}
+
+float InjectorModel::getInjectorMassFlowRate() const {
+	// TODO: injector flow dependent upon rail pressure (and temperature/ethanol content?)
+	auto injectorVolumeFlow = CONFIG(injector.flow);
+	return convertToGramsPerSecond(injectorVolumeFlow);
+}
+
+float InjectorModel::getDeadtime() const {
+	return interpolate2d(
+		"lag",
+		ENGINE(sensors.vBatt),
+		engineConfiguration->injector.battLagCorrBins,
+		engineConfiguration->injector.battLagCorr
+	);
+}
+
+float InjectorModelBase::getInjectionDuration(float fuelMassGram) const {
+	// TODO: support injector nonlinearity correction
+
+	floatms_t baseDuration = fuelMassGram / m_massFlowRate * 1000;
+	return baseDuration + m_deadtime;
+}

firmware/controllers/algo/fuel/injector_model.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "engine.h"
+
+class InjectorModelBase {
+public:
+	void prepare();
+	floatms_t getInjectionDuration(float fuelMassGram) const;
+
+	virtual floatms_t getDeadtime() const = 0;
+	virtual float getInjectorMassFlowRate() const = 0;
+
+private:
+	float m_deadtime = 0;
+	float m_massFlowRate = 0;
+};
+
+class InjectorModel : public InjectorModelBase {
+public:
+	DECLARE_ENGINE_PTR;
+
+	floatms_t getDeadtime() const override;
+	float getInjectorMassFlowRate() const override;
+};

firmware/controllers/algo/fuel_math.cpp

@@ -28,6 +28,7 @@
 #include "speed_density_airmass.h"
 #include "fuel_math.h"
 #include "fuel_computer.h"
+#include "injector_model.h"
 #include "interpolation.h"
 #include "engine_configuration.h"
 #include "allsensors.h"
@@ -193,6 +194,7 @@ AirmassModelBase* getAirmassModel(DECLARE_ENGINE_PARAMETER_SIGNATURE) {
 }
 
 static FuelComputer fuelComputer(afrMap);
+static InjectorModel injectorModel;
 
 /**
  * per-cylinder fuel amount
@@ -370,7 +372,9 @@ void initFuelMap(DECLARE_ENGINE_PARAMETER_SIGNATURE) {
 	INJECT_ENGINE_REFERENCE(&sdAirmass);
 	INJECT_ENGINE_REFERENCE(&mafAirmass);
 	INJECT_ENGINE_REFERENCE(&alphaNAirmass);
+
 	INJECT_ENGINE_REFERENCE(&fuelComputer);
+	INJECT_ENGINE_REFERENCE(&injectorModel);
 
 #if (IGN_LOAD_COUNT == FUEL_LOAD_COUNT) && (IGN_RPM_COUNT == FUEL_RPM_COUNT)
 	fuelPhaseMap.init(config->injectionPhase, config->injPhaseLoadBins, config->injPhaseRpmBins);

unit_tests/tests/ignition_injection/test_injector_model.cpp

@@ -0,0 +1,55 @@
+#include "engine_test_helper.h"
+#include "injector_model.h"
+#include "mocks.h"
+
+#include "gtest/gtest.h"
+
+using ::testing::StrictMock;
+
+class MockInjectorModel : public InjectorModelBase {
+public:
+	MOCK_METHOD(floatms_t, getDeadtime, (), (const, override));
+	MOCK_METHOD(float, getInjectorMassFlowRate, (), (const, override));
+};
+
+TEST(InjectorModel, Prepare) {
+	StrictMock<MockInjectorModel> dut;
+
+	EXPECT_CALL(dut, getDeadtime());
+	EXPECT_CALL(dut, getInjectorMassFlowRate());
+
+	dut.prepare();
+}
+
+TEST(InjectorModel, getInjectionDuration) {
+	StrictMock<MockInjectorModel> dut;
+
+	EXPECT_CALL(dut, getDeadtime())
+		.WillRepeatedly(Return(2.0f));
+	EXPECT_CALL(dut, getInjectorMassFlowRate())
+		.WillRepeatedly(Return(4.8f)); // 400cc/min
+
+	dut.prepare();
+
+	EXPECT_NEAR(dut.getInjectionDuration(0.01f), 10 / 4.8f + 2.0f, EPS4D);
+	EXPECT_NEAR(dut.getInjectionDuration(0.02f), 20 / 4.8f + 2.0f, EPS4D);
+}
+
+TEST(InjectorModel, Deadtime) {
+	WITH_ENGINE_TEST_HELPER(TEST_ENGINE);
+
+	// Some test data in the injector correction table
+	for (size_t i = 0; i < efi::size(engineConfiguration->injector.battLagCorr); i++) {
+		CONFIG(injector.battLagCorr)[i] = 2 * i;
+		CONFIG(injector.battLagCorrBins)[i] = i;
+	}
+
+	InjectorModel dut;
+	INJECT_ENGINE_REFERENCE(&dut);
+
+	engine->sensors.vBatt = 3;
+	EXPECT_EQ(dut.getDeadtime(), 6);
+
+	engine->sensors.vBatt = 7;
+	EXPECT_EQ(dut.getDeadtime(), 14);
+}

unit_tests/tests/tests.mk

@@ -13,6 +13,7 @@ TESTS_SRC_CPP = \
 	tests/ignition_injection/test_ignition_scheduling.cpp \
 	tests/ignition_injection/test_fuelCut.cpp \
 	tests/ignition_injection/test_fuel_computer.cpp \
+	tests/ignition_injection/test_injector_model.cpp \
 	tests/test_util.cpp \
 	tests/test_ion.cpp \
 	tests/test_aux_valves.cpp \