lambda conversion

firmware/Makefile

@@ -123,7 +123,7 @@ CPPSRC = $(ALLCPPSRC) \
           analog_input.cpp \
           can.cpp \
           can_helper.cpp \
-          lambda_lookup.cpp \
+          lambda_conversion.cpp \
           pwm.cpp \
           pump_dac.cpp \
           sampling.cpp \

firmware/lambda_conversion.cpp

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "sampling.h"
+
+static float GetPhi(float pumpCurrent)
+{
+    // This estimation is accurate within 0.5% from 0.8 to 1.0, and 0.01% from 1 to 1.2 lambda when compared to the lookup table in the Bosch datasheet
+    float gain = pumpCurrent > 0 ? -0.28299f : -0.44817f;
+
+    return gain * pumpCurrent + 0.99559f;
+}
+
+float GetLambda()
+{
+    float pumpCurrent = GetPumpNominalCurrent();
+
+    // Lambda is reciprocal of phi
+    return 1 / GetPhi(pumpCurrent);
+}

firmware/lambda_conversion.h

@@ -0,0 +1,3 @@
+#pragma once
+
+float GetLambda();

firmware/lambda_lookup.cpp

@@ -1,3 +0,0 @@
-
-static const float pumpCurrentMa[24] = { -2.0f, -1.602f, -1.243f, -0.927f, -0.8f, -0.652f, -0.405f, -0.183f, -0.106f, -0.04f, 0.0f, 0.015f, 0.097f, 0.193f, 0.25f, 0.329f, 0.671f, 0.938f, 1.15f, 1.385f, 1.7f, 2.0f, 2.15f, 2.25 };
-static const float phi[24] = { 1.538461538f, 1.428571429f, 1.333333333f, 1.25f, 1.216545012f, 1.176470588f, 1.111111111f, 1.052631579f, 1.030927835f, 1.01010101f, 0.997008973f, 0.99009901f, 0.952380952f, 0.909090909f, 0.883392226f, 0.848176421f, 0.699790063f, 0.587889477f, 0.502512563f, 0.410846343f, 0.292997363f, 0.185494342f, 0.133226752f, 0.098823994 };

firmware/main.cpp

@@ -7,6 +7,7 @@
 #include "pump_control.h"
 #include "pump_dac.h"
 #include "sampling.h"
+#include "lambda_conversion.h"
 
 static const UARTConfig uartCfg =
 {
@@ -58,7 +59,7 @@ int main() {
     }*/
 
     while(1) {
-        size_t writeCount = chsnprintf(strBuffer, 200, "%.4f\t%.2f\t%.2f\n", GetSensorInternalResistance(), nernstVolt, GetPumpNominalCurrent());
+        size_t writeCount = chsnprintf(strBuffer, 200, "%.4f\t%.2f\t%.3f\n", GetSensorInternalResistance(), GetNernstDc(), GetLambda());
         uartStartSend(&UARTD1, writeCount, strBuffer);
 
         chThdSleepMilliseconds(5);