random fixes related to current sensing

src/common/base_classes/CurrentSense.cpp

@@ -17,8 +17,12 @@ float CurrentSense::getDCCurrent(float motor_electrical_angle){
         i_alpha = current.a;  
         i_beta = _1_SQRT3 * current.a + _2_SQRT3 * current.b;
     }else{
-        i_alpha = 2*(current.a - (current.b - current.c))/3.0;    
-        i_beta = _2_SQRT3 *( current.b  - current.c );
+        // signal filtering using identity a + b + c = 0. Assumes measurement error is normally distributed.
+        float mid = (1.f/3) * (current.a + current.b + current.c);
+        float a = current.a - mid;
+        float b = current.b - mid;
+        i_alpha = a;
+        i_beta = _1_SQRT3 * a + _2_SQRT3 * b;
     }
 
     // if motor angle provided function returns signed value of the current
@@ -44,9 +48,13 @@ DQCurrent_s CurrentSense::getFOCCurrents(float angle_el){
         // if only two measured currents
         i_alpha = current.a;  
         i_beta = _1_SQRT3 * current.a + _2_SQRT3 * current.b;
-    }else{
-        i_alpha = 0.6666667*(current.a - (current.b - current.c));    
-        i_beta = _2_SQRT3 *( current.b  - current.c );
+    } else {
+        // signal filtering using identity a + b + c = 0. Assumes measurement error is normally distributed.
+        float mid = (1.f/3) * (current.a + current.b + current.c);
+        float a = current.a - mid;
+        float b = current.b - mid;
+        i_alpha = a;
+        i_beta = _1_SQRT3 * a + _2_SQRT3 * b;
     }
 
     // calculate park transform

src/current_sense/InlineCurrentSense.cpp

@@ -28,21 +28,23 @@ void InlineCurrentSense::init(){
 }
 // Function finding zero offsets of the ADC
 void InlineCurrentSense::calibrateOffsets(){
+    const int calibration_rounds = 1000;
+
     // find adc offset = zero current voltage
-    offset_ia =0;
-    offset_ib= 0;
-    offset_ic= 0;
+    offset_ia = 0;
+    offset_ib = 0;
+    offset_ic = 0;
     // read the adc voltage 1000 times ( arbitrary number )
-    for (int i = 0; i < 1000; i++) {
+    for (int i = 0; i < calibration_rounds; i++) {
         offset_ia += _readADCVoltage(pinA);
         offset_ib += _readADCVoltage(pinB);
         if(_isset(pinC)) offset_ic += _readADCVoltage(pinC);
         _delay(1);
     }
     // calculate the mean offsets
-    offset_ia = offset_ia / 1000.0;
-    offset_ib = offset_ib / 1000.0;
-    if(_isset(pinC)) offset_ic = offset_ic / 500.0;
+    offset_ia = offset_ia / calibration_rounds;
+    offset_ib = offset_ib / calibration_rounds;
+    if(_isset(pinC)) offset_ic = offset_ic / calibration_rounds;
 }
 
 // read all three phase currents (if possible 2 or 3)

src/current_sense/InlineCurrentSense.h

@@ -29,9 +29,9 @@ class InlineCurrentSense: public CurrentSense{
     // ADC measuremnet gain for each phase
     // support for different gains for different phases of more commonly - inverted phase currents
     // this should be automated later
-  	int gain_a; //!< phase A gain 
-  	int gain_b; //!< phase B gain 
-  	int gain_c; //!< phase C gain 
+    float gain_a; //!< phase A gain
+    float gain_b; //!< phase B gain
+    float gain_c; //!< phase C gain
 
   private: