Merge pull request #436 from rosflight/ptt/pitotspeed

Changes pitot velocity to indicated air speed (ias)

Author: iandareid

include/sensors.h

@@ -146,7 +146,7 @@ class Sensors : public ParamListenerInterface
     float imu_temperature = 0;
     uint64_t imu_time = 0;
 
-    float diff_pressure_velocity = 0;
+    float diff_pressure_ias = 0;
     float diff_pressure = 0;
     float diff_pressure_temp = 0;
 

src/comm_manager.cpp

@@ -404,7 +404,7 @@ void CommManager::send_rc_raw(void)
 
 void CommManager::send_diff_pressure(void)
 {
-  comm_link_.send_diff_pressure(sysid_, RF_.sensors_.data().diff_pressure_velocity,
+  comm_link_.send_diff_pressure(sysid_, RF_.sensors_.data().diff_pressure_ias,
                                 RF_.sensors_.data().diff_pressure,
                                 RF_.sensors_.data().diff_pressure_temp);
 }

src/sensors.cpp

@@ -558,10 +558,9 @@ void Sensors::correct_diff_pressure()
   if (!diff_pressure_calibrated_) { calibrate_diff_pressure(); }
   data_.diff_pressure -= rf_.params_.get_param_float(PARAM_DIFF_PRESS_BIAS);
 
-  float atm = 101325.0f;
-  if (data_.baro_present) { atm = data_.baro_pressure; }
-  data_.diff_pressure_velocity = turbomath::fsign(data_.diff_pressure) * 24.574f
-    / turbomath::inv_sqrt((turbomath::fabs(data_.diff_pressure) * data_.diff_pressure_temp / atm));
+  // compute indicated air speed
+  data_.diff_pressure_ias = turbomath::fsign(data_.diff_pressure)
+    * sqrt((fabs(data_.diff_pressure)/(0.5*1.225)));
 }
 
 void Sensors::update_battery_monitor_multipliers()